From 994e0467c9c5e8024348af24ac7004057e314b87 Mon Sep 17 00:00:00 2001
From: mike kowalski <michal_kowalski@hotmail.com>
Date: Thu, 17 Nov 2022 21:09:26 -0800
Subject: [PATCH] Add syntax coloring to the XML Dialog

Co-authored-by: Rafael Siejakowski <rs@rs-math.net>

Use GTKSourceView4 to implement syntax highlighting in the XML Dialog
for CSS editing (both the contents of the <style> tag and inline styles)
as well as for the SVG path `d` attribute and the `points` attribute of
poly{line|gon} elements. Consistently-styled XML coloring is also used
in the XML tree shown in the dialog, by recognizing XML elements and
attributes.

Several additional UI improvements are made to the XML Dialog:

* When editing the `d` attribute, a number-rounding button is available.
* The `d` attribute and inline CSS are automatically reformatted for
  better readability.
* The attribute editing popover does not close on Enter press in these
  modes. Its resizing behavior and timings are improved.
* The superfluous `svg:` namespace prefix is not shown in the XML tree.
  When the user creates a new node via the dialog, the prefix is
  accepted but not required.
* A validation step is added for new element nodes in SVG namespace; any
  invalid elements are highlighted as errors.

The user can select the coloring theme and the monospaced font for use
in the XML Dialog. Two custom made, Inkscape-specific themes are added,
one for dark and one for light UI mode. The GTKSourceView4 library is
added as a dependency in the msys2 and Snap packaging environments.

Closes https://gitlab.com/inkscape/inbox/-/issues/4263
Closes https://gitlab.com/inkscape/inbox/-/issues/4264
---
 CMakeLists.txt                                |   2 +
 CMakeScripts/DefineDependsandFlags.cmake      |  12 +
 CMakeScripts/InstallMSYS2.cmake               |   4 +
 buildtools/msys2installdeps.sh                |   1 +
 config.h.cmake                                |   3 +
 po/POTFILES.ui.in                             |   1 +
 .../hicolor/scalable/actions/rounding.svg     |  83 +++
 .../symbolic/actions/rounding-symbolic.svg    |  83 +++
 .../symbolic/actions/rounding-symbolic.svg    |  83 +++
 share/ui/CMakeLists.txt                       |   5 +-
 share/ui/attribute-edit-component.glade       | 335 +++++++++
 share/ui/inline-css.lang                      |  10 +
 share/ui/style.css                            |  21 +-
 share/ui/svgd.lang                            | 229 ++++++
 share/ui/svgpoints.lang                       |  47 ++
 share/ui/syntax-themes/syntax-theme-dark.xml  |  77 ++
 share/ui/syntax-themes/syntax-theme-light.xml |  79 ++
 share/ui/syntax-themes/syntax-theme-none.xml  |  17 +
 snap/snapcraft.yaml                           |   3 +
 src/attribute-rel-util.cpp                    |  33 +
 src/attribute-rel-util.h                      |  27 +-
 src/inkscape.cpp                              |   9 +-
 src/object/sp-factory.cpp                     |  19 +-
 src/object/sp-factory.h                       |   1 +
 src/preferences.h                             |  15 +
 src/ui/CMakeLists.txt                         |   2 +
 src/ui/dialog/attrdialog.cpp                  | 697 +++++++++++-------
 src/ui/dialog/attrdialog.h                    |  74 +-
 src/ui/dialog/inkscape-preferences.cpp        |  70 +-
 src/ui/dialog/inkscape-preferences.h          |   1 +
 src/ui/dialog/xml-tree.cpp                    | 193 +++--
 src/ui/dialog/xml-tree.h                      |  19 +-
 src/ui/icon-loader.cpp                        |   5 +
 src/ui/shortcuts.cpp                          |   4 +-
 src/ui/syntax.cpp                             | 395 ++++++++++
 src/ui/syntax.h                               | 134 ++++
 src/ui/themes.cpp                             |  73 +-
 src/ui/themes.h                               |  53 +-
 src/ui/util.cpp                               |  28 +-
 src/ui/util.h                                 |  19 +-
 src/ui/widget/shapeicon.cpp                   |  25 +-
 src/ui/widget/shapeicon.h                     |  13 +-
 src/widgets/sp-xmlview-tree.cpp               | 140 +++-
 src/widgets/sp-xmlview-tree.h                 |  12 +-
 44 files changed, 2698 insertions(+), 458 deletions(-)
 create mode 100644 share/icons/hicolor/scalable/actions/rounding.svg
 create mode 100644 share/icons/hicolor/symbolic/actions/rounding-symbolic.svg
 create mode 100644 share/icons/multicolor/symbolic/actions/rounding-symbolic.svg
 create mode 100644 share/ui/attribute-edit-component.glade
 create mode 100644 share/ui/inline-css.lang
 create mode 100644 share/ui/svgd.lang
 create mode 100644 share/ui/svgpoints.lang
 create mode 100644 share/ui/syntax-themes/syntax-theme-dark.xml
 create mode 100644 share/ui/syntax-themes/syntax-theme-light.xml
 create mode 100644 share/ui/syntax-themes/syntax-theme-none.xml
 create mode 100644 src/ui/syntax.cpp
 create mode 100644 src/ui/syntax.h

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2fb79b801b..5dcbf95ed7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -123,6 +123,7 @@ option(WITH_LIBCDR "Compile with support of libcdr for CorelDRAW Diagrams" ON)
 option(WITH_LIBVISIO "Compile with support of libvisio for Microsoft Visio Diagrams" ON)
 option(WITH_LIBWPG "Compile with support of libwpg for WordPerfect Graphics" ON)
 option(WITH_GSPELL "Compile with support of gspell" ON)
+option(WITH_GSOURCEVIEW "Compile with support of gsourceview (text syntax coloring)" ON)
 option(WITH_NLS "Compile with Native Language Support (using gettext)" ON)
 option(WITH_JEMALLOC "Compile with JEMALLOC support" OFF)
 option(WITH_ASAN "Compile with Clang's AddressSanitizer (for debugging purposes)" OFF)
@@ -282,6 +283,7 @@ message("ENABLE_POPPLER:          ${ENABLE_POPPLER}")
 message("ENABLE_POPPLER_CAIRO:    ${ENABLE_POPPLER_CAIRO}")
 message("WITH_GNU_READLINE:       ${WITH_GNU_READLINE}")
 message("WITH_GSPELL:             ${WITH_GSPELL}")
+message("WITH_GSOURCEVIEW:        ${WITH_GSOURCEVIEW}")
 message("WITH_IMAGE_MAGICK:       ${WITH_IMAGE_MAGICK}")
 message("WITH_GRAPHICS_MAGICK:    ${WITH_GRAPHICS_MAGICK}")
 message("WITH_LIBCDR:             ${WITH_LIBCDR}")
diff --git a/CMakeScripts/DefineDependsandFlags.cmake b/CMakeScripts/DefineDependsandFlags.cmake
index ee4ca22582..de815251bf 100644
--- a/CMakeScripts/DefineDependsandFlags.cmake
+++ b/CMakeScripts/DefineDependsandFlags.cmake
@@ -283,6 +283,18 @@ if(WITH_GSPELL)
     endif()
 endif()
 
+if(WITH_GSOURCEVIEW)
+    pkg_check_modules(GSOURCEVIEW gtksourceview-4)
+    if("${GSOURCEVIEW_FOUND}")
+        message(STATUS "Using gtksourceview-4")
+        list(APPEND INKSCAPE_INCS_SYS ${GSOURCEVIEW_INCLUDE_DIRS})
+        sanitize_ldflags_for_libs(GSOURCEVIEW_LDFLAGS)
+        list(APPEND INKSCAPE_LIBS ${GSOURCEVIEW_LDFLAGS})
+    else()
+        set(WITH_GSOURCEVIEW OFF)
+    endif()
+endif()
+
 find_package(Boost 1.19.0 REQUIRED COMPONENTS filesystem)
 
 if (CMAKE_COMPILER_IS_GNUCC AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 7 AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 9)
diff --git a/CMakeScripts/InstallMSYS2.cmake b/CMakeScripts/InstallMSYS2.cmake
index 2d732ac6af..99d74b2621 100644
--- a/CMakeScripts/InstallMSYS2.cmake
+++ b/CMakeScripts/InstallMSYS2.cmake
@@ -59,6 +59,7 @@ if(WIN32)
     ${MINGW_BIN}/libgspell-1-[0-9]*.dll
     ${MINGW_BIN}/libgtk-3-[0-9]*.dll
     ${MINGW_BIN}/libgtkmm-3.0-[0-9]*.dll
+    ${MINGW_BIN}/libgtksourceview-4-[0-9]*.dll
     ${MINGW_BIN}/libharfbuzz-[0-9]*.dll
     ${MINGW_BIN}/libheif.dll
     ${MINGW_BIN}/libiconv-[0-9]*.dll
@@ -200,6 +201,9 @@ if(WIN32)
   install(DIRECTORY ${MINGW_PATH}/share/glib-2.0/schemas
     DESTINATION share/glib-2.0)
 
+  install(DIRECTORY ${MINGW_PATH}/share/gtksourceview-4
+    DESTINATION share)
+
   # fontconfig
   install(DIRECTORY ${MINGW_PATH}/etc/fonts
     DESTINATION etc
diff --git a/buildtools/msys2installdeps.sh b/buildtools/msys2installdeps.sh
index 98dd4c5623..7d68e3d640 100644
--- a/buildtools/msys2installdeps.sh
+++ b/buildtools/msys2installdeps.sh
@@ -66,6 +66,7 @@ $ARCH-libwpg \
 $ARCH-aspell \
 $ARCH-aspell-en \
 $ARCH-gspell \
+$ARCH-gtksourceview4 \
 $ARCH-graphicsmagick \
 $ARCH-libjxl
 
diff --git a/config.h.cmake b/config.h.cmake
index 29a5826e4a..5035015589 100644
--- a/config.h.cmake
+++ b/config.h.cmake
@@ -71,6 +71,9 @@
 /* enable gtk spelling widget and built-in spellchecker */
 #cmakedefine WITH_GSPELL 1
 
+/* enable gtk syntax coloring text view widget */
+#cmakedefine WITH_GSOURCEVIEW 1
+
 /* Image/Graphics Magick++ support for bitmap effects */
 #cmakedefine WITH_MAGICK 1
 
diff --git a/po/POTFILES.ui.in b/po/POTFILES.ui.in
index 493cdb5b47..7eea602a5c 100644
--- a/po/POTFILES.ui.in
+++ b/po/POTFILES.ui.in
@@ -1,3 +1,4 @@
+../share/ui/attribute-edit-component.glade
 ../share/ui/color-palette.glade
 ../share/ui/command-palette-operation.glade
 ../share/ui/completion-box.glade
diff --git a/share/icons/hicolor/scalable/actions/rounding.svg b/share/icons/hicolor/scalable/actions/rounding.svg
new file mode 100644
index 0000000000..233d16fa00
--- /dev/null
+++ b/share/icons/hicolor/scalable/actions/rounding.svg
@@ -0,0 +1,83 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!-- Created with Inkscape (http://www.inkscape.org/) and export_objects.py -->
+
+<svg
+   version="1.1"
+   id="svg1"
+   width="16"
+   height="16"
+   viewBox="0 0 16 16"
+   sodipodi:docname="rounding-symbolic.svg"
+   inkscape:version="1.2 (dc2aeda, 2022-05-15)"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:svg="http://www.w3.org/2000/svg">
+  <defs
+     id="defs140" />
+  <sodipodi:namedview
+     objecttolerance="10"
+     gridtolerance="10"
+     guidetolerance="10"
+     id="namedview"
+     showgrid="true"
+     inkscape:zoom="51.72747"
+     inkscape:cx="4.407716"
+     inkscape:cy="11.367268"
+     inkscape:window-width="1424"
+     inkscape:window-height="703"
+     inkscape:window-x="0"
+     inkscape:window-y="38"
+     inkscape:window-maximized="0"
+     inkscape:current-layer="svg1"
+     pagecolor="#ffffff"
+     bordercolor="#000000"
+     borderopacity="0.25"
+     inkscape:showpageshadow="2"
+     inkscape:pageopacity="0.0"
+     inkscape:pagecheckerboard="0"
+     inkscape:deskcolor="#d1d1d1">
+    <inkscape:grid
+       type="xygrid"
+       id="grid" />
+  </sodipodi:namedview>
+  <path
+     inkscape:connector-curvature="0"
+     id="gtk-edit"
+     d="M 0,4.058274e-4 H 16 V 16.00031 H 0 Z"
+     style="opacity:0;fill:none;stroke-width:0.999997" />
+  <g
+     id="g1389"
+     transform="matrix(0.625581,0.22774992,-0.22774992,0.625581,6.6459276,2.9316306)"
+     style="stroke-width:1.50207">
+    <path
+       inkscape:connector-curvature="0"
+       d="m -1.1859356,8.0378199 c -0.1104384,1.1352791 0.60859818,1.941859 1.61593659,1.831088 L 7.9646425,9.2204517 8.8554893,11.709436 11.085942,11.398158 10.041742,8.9747891 12.647291,8.6938208 11.86024,6.6550523 9.2159925,7.0530498 6.0102511,0.20363107 C 5.6024626,-0.72404869 4.5444759,-0.9435496 3.6164643,-0.28018086 L 7.1154601,7.2852992 Z"
+       id="path12477"
+       style="stroke-width:1.50207" />
+    <path
+       d="m 10.928696,5.0545541 c -0.828428,1.4348802 -0.142947,3.3815712 1.531071,4.3480657 1.674017,0.9664942 3.702642,0.5867935 4.53107,-0.8480868 0.82843,-1.43488 0.142946,-3.3815717 -1.53107,-4.3480657 -1.674018,-0.9664945 -3.702643,-0.5867936 -4.531071,0.8480868 z m 1.73204,0.999994 c 0.35503,-0.6149273 1.224823,-0.7774629 1.941888,-0.3634653 0.71793,0.4144973 1.011202,1.248529 0.656173,1.8634563 C 14.903769,8.1694665 14.034841,8.3325022 13.31691,7.9180046 12.599845,7.504007 12.305708,6.6694755 12.660736,6.0545481 Z"
+       id="path61250"
+       inkscape:connector-curvature="0"
+       style="stroke-width:1.50207" />
+    <path
+       id="path61253"
+       d="m 6.9286961,11.982758 c -0.8284285,1.43488 -0.1429467,3.381571 1.5310709,4.348066 1.674017,0.966494 3.702642,0.586793 4.531071,-0.848088 0.828428,-1.43488 0.142946,-3.381571 -1.531071,-4.348066 -1.6740176,-0.966494 -3.7026424,-0.586793 -4.5310709,0.848088 z m 1.7320405,0.999994 c 0.3550285,-0.614928 1.2248222,-0.777463 1.9418874,-0.363466 0.717931,0.414497 1.011202,1.248529 0.656173,1.863456 C 10.903769,15.09767 10.03484,15.260705 9.3169104,14.846208 8.5998452,14.432211 8.3057082,13.597679 8.6607366,12.982752 Z"
+       inkscape:connector-curvature="0"
+       style="stroke-width:1.50207" />
+  </g>
+  <g
+     aria-label="12"
+     id="text1445"
+     style="fill:#000000;stroke-width:0.977807"
+     transform="matrix(1.0226962,0,0,1.0226962,-0.18044148,-1.1812468)">
+    <path
+       d="m 0.67883548,3.1089373 q 0.30062665,0 0.58455212,-0.050104 Q 1.5473128,3.0087285 1.7727828,2.8918181 2.0066035,2.7749077 2.1652676,2.5911914 2.3322824,2.4074751 2.3823868,2.1402514 H 3.1590057 V 7.9857697 H 2.1151632 V 3.860504 H 0.67883548 Z"
+       id="path1647"
+       style="fill:#000000;stroke-width:0.977807" />
+    <path
+       d="M 7.9797421,7.9857697 H 3.9880881 Q 3.9964389,7.2592553 4.3388192,6.7164572 4.6811996,6.1736591 5.2741022,5.7728235 5.5580273,5.564055 5.8670047,5.371988 6.1759821,5.1715702 6.4348551,4.9461002 6.693728,4.7206302 6.8607428,4.4617573 7.0277576,4.1945336 7.0361084,3.8521532 q 0,-0.158664 -0.041754,-0.3340296 Q 6.9609517,3.3344073 6.8523921,3.184094 6.7438325,3.0254299 6.5517654,2.925221 6.3596984,2.8166614 6.050721,2.8166614 q -0.2839252,0 -0.4759922,0.1169104 Q 5.3910125,3.0421314 5.2741022,3.2425492 5.1655425,3.4346162 5.1070873,3.7018399 5.0569829,3.9690636 5.0486322,4.278041 H 4.0966478 q 0,-0.4843429 0.1252611,-0.8935292 Q 4.3555207,2.9669747 4.6143937,2.6663481 4.8732666,2.3657214 5.2406992,2.1987066 5.6164825,2.0233411 6.1091762,2.0233411 q 0.5344474,0 0.8935292,0.1753655 0.3590819,0.1753656 0.5762011,0.4425893 0.22547,0.2672237 0.3173282,0.5845518 0.091858,0.3089774 0.091858,0.5929026 0,0.3507311 -0.1085596,0.6346562 Q 7.7709735,4.7373317 7.5872573,4.9795032 7.403541,5.2133239 7.1697202,5.4137417 6.9358995,5.6141595 6.6853773,5.789525 6.4348551,5.9648906 6.1843329,6.1235546 5.9338107,6.2822187 5.7166914,6.4408828 5.5079229,6.5995468 5.3492588,6.7749124 5.1905948,6.9419272 5.1321396,7.1339942 h 2.8476025 z"
+       id="path1649"
+       style="fill:#000000;stroke-width:0.977807" />
+  </g>
+</svg>
diff --git a/share/icons/hicolor/symbolic/actions/rounding-symbolic.svg b/share/icons/hicolor/symbolic/actions/rounding-symbolic.svg
new file mode 100644
index 0000000000..233d16fa00
--- /dev/null
+++ b/share/icons/hicolor/symbolic/actions/rounding-symbolic.svg
@@ -0,0 +1,83 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!-- Created with Inkscape (http://www.inkscape.org/) and export_objects.py -->
+
+<svg
+   version="1.1"
+   id="svg1"
+   width="16"
+   height="16"
+   viewBox="0 0 16 16"
+   sodipodi:docname="rounding-symbolic.svg"
+   inkscape:version="1.2 (dc2aeda, 2022-05-15)"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:svg="http://www.w3.org/2000/svg">
+  <defs
+     id="defs140" />
+  <sodipodi:namedview
+     objecttolerance="10"
+     gridtolerance="10"
+     guidetolerance="10"
+     id="namedview"
+     showgrid="true"
+     inkscape:zoom="51.72747"
+     inkscape:cx="4.407716"
+     inkscape:cy="11.367268"
+     inkscape:window-width="1424"
+     inkscape:window-height="703"
+     inkscape:window-x="0"
+     inkscape:window-y="38"
+     inkscape:window-maximized="0"
+     inkscape:current-layer="svg1"
+     pagecolor="#ffffff"
+     bordercolor="#000000"
+     borderopacity="0.25"
+     inkscape:showpageshadow="2"
+     inkscape:pageopacity="0.0"
+     inkscape:pagecheckerboard="0"
+     inkscape:deskcolor="#d1d1d1">
+    <inkscape:grid
+       type="xygrid"
+       id="grid" />
+  </sodipodi:namedview>
+  <path
+     inkscape:connector-curvature="0"
+     id="gtk-edit"
+     d="M 0,4.058274e-4 H 16 V 16.00031 H 0 Z"
+     style="opacity:0;fill:none;stroke-width:0.999997" />
+  <g
+     id="g1389"
+     transform="matrix(0.625581,0.22774992,-0.22774992,0.625581,6.6459276,2.9316306)"
+     style="stroke-width:1.50207">
+    <path
+       inkscape:connector-curvature="0"
+       d="m -1.1859356,8.0378199 c -0.1104384,1.1352791 0.60859818,1.941859 1.61593659,1.831088 L 7.9646425,9.2204517 8.8554893,11.709436 11.085942,11.398158 10.041742,8.9747891 12.647291,8.6938208 11.86024,6.6550523 9.2159925,7.0530498 6.0102511,0.20363107 C 5.6024626,-0.72404869 4.5444759,-0.9435496 3.6164643,-0.28018086 L 7.1154601,7.2852992 Z"
+       id="path12477"
+       style="stroke-width:1.50207" />
+    <path
+       d="m 10.928696,5.0545541 c -0.828428,1.4348802 -0.142947,3.3815712 1.531071,4.3480657 1.674017,0.9664942 3.702642,0.5867935 4.53107,-0.8480868 0.82843,-1.43488 0.142946,-3.3815717 -1.53107,-4.3480657 -1.674018,-0.9664945 -3.702643,-0.5867936 -4.531071,0.8480868 z m 1.73204,0.999994 c 0.35503,-0.6149273 1.224823,-0.7774629 1.941888,-0.3634653 0.71793,0.4144973 1.011202,1.248529 0.656173,1.8634563 C 14.903769,8.1694665 14.034841,8.3325022 13.31691,7.9180046 12.599845,7.504007 12.305708,6.6694755 12.660736,6.0545481 Z"
+       id="path61250"
+       inkscape:connector-curvature="0"
+       style="stroke-width:1.50207" />
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+       inkscape:connector-curvature="0"
+       style="stroke-width:1.50207" />
+  </g>
+  <g
+     aria-label="12"
+     id="text1445"
+     style="fill:#000000;stroke-width:0.977807"
+     transform="matrix(1.0226962,0,0,1.0226962,-0.18044148,-1.1812468)">
+    <path
+       d="m 0.67883548,3.1089373 q 0.30062665,0 0.58455212,-0.050104 Q 1.5473128,3.0087285 1.7727828,2.8918181 2.0066035,2.7749077 2.1652676,2.5911914 2.3322824,2.4074751 2.3823868,2.1402514 H 3.1590057 V 7.9857697 H 2.1151632 V 3.860504 H 0.67883548 Z"
+       id="path1647"
+       style="fill:#000000;stroke-width:0.977807" />
+    <path
+       d="M 7.9797421,7.9857697 H 3.9880881 Q 3.9964389,7.2592553 4.3388192,6.7164572 4.6811996,6.1736591 5.2741022,5.7728235 5.5580273,5.564055 5.8670047,5.371988 6.1759821,5.1715702 6.4348551,4.9461002 6.693728,4.7206302 6.8607428,4.4617573 7.0277576,4.1945336 7.0361084,3.8521532 q 0,-0.158664 -0.041754,-0.3340296 Q 6.9609517,3.3344073 6.8523921,3.184094 6.7438325,3.0254299 6.5517654,2.925221 6.3596984,2.8166614 6.050721,2.8166614 q -0.2839252,0 -0.4759922,0.1169104 Q 5.3910125,3.0421314 5.2741022,3.2425492 5.1655425,3.4346162 5.1070873,3.7018399 5.0569829,3.9690636 5.0486322,4.278041 H 4.0966478 q 0,-0.4843429 0.1252611,-0.8935292 Q 4.3555207,2.9669747 4.6143937,2.6663481 4.8732666,2.3657214 5.2406992,2.1987066 5.6164825,2.0233411 6.1091762,2.0233411 q 0.5344474,0 0.8935292,0.1753655 0.3590819,0.1753656 0.5762011,0.4425893 0.22547,0.2672237 0.3173282,0.5845518 0.091858,0.3089774 0.091858,0.5929026 0,0.3507311 -0.1085596,0.6346562 Q 7.7709735,4.7373317 7.5872573,4.9795032 7.403541,5.2133239 7.1697202,5.4137417 6.9358995,5.6141595 6.6853773,5.789525 6.4348551,5.9648906 6.1843329,6.1235546 5.9338107,6.2822187 5.7166914,6.4408828 5.5079229,6.5995468 5.3492588,6.7749124 5.1905948,6.9419272 5.1321396,7.1339942 h 2.8476025 z"
+       id="path1649"
+       style="fill:#000000;stroke-width:0.977807" />
+  </g>
+</svg>
diff --git a/share/icons/multicolor/symbolic/actions/rounding-symbolic.svg b/share/icons/multicolor/symbolic/actions/rounding-symbolic.svg
new file mode 100644
index 0000000000..233d16fa00
--- /dev/null
+++ b/share/icons/multicolor/symbolic/actions/rounding-symbolic.svg
@@ -0,0 +1,83 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!-- Created with Inkscape (http://www.inkscape.org/) and export_objects.py -->
+
+<svg
+   version="1.1"
+   id="svg1"
+   width="16"
+   height="16"
+   viewBox="0 0 16 16"
+   sodipodi:docname="rounding-symbolic.svg"
+   inkscape:version="1.2 (dc2aeda, 2022-05-15)"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:svg="http://www.w3.org/2000/svg">
+  <defs
+     id="defs140" />
+  <sodipodi:namedview
+     objecttolerance="10"
+     gridtolerance="10"
+     guidetolerance="10"
+     id="namedview"
+     showgrid="true"
+     inkscape:zoom="51.72747"
+     inkscape:cx="4.407716"
+     inkscape:cy="11.367268"
+     inkscape:window-width="1424"
+     inkscape:window-height="703"
+     inkscape:window-x="0"
+     inkscape:window-y="38"
+     inkscape:window-maximized="0"
+     inkscape:current-layer="svg1"
+     pagecolor="#ffffff"
+     bordercolor="#000000"
+     borderopacity="0.25"
+     inkscape:showpageshadow="2"
+     inkscape:pageopacity="0.0"
+     inkscape:pagecheckerboard="0"
+     inkscape:deskcolor="#d1d1d1">
+    <inkscape:grid
+       type="xygrid"
+       id="grid" />
+  </sodipodi:namedview>
+  <path
+     inkscape:connector-curvature="0"
+     id="gtk-edit"
+     d="M 0,4.058274e-4 H 16 V 16.00031 H 0 Z"
+     style="opacity:0;fill:none;stroke-width:0.999997" />
+  <g
+     id="g1389"
+     transform="matrix(0.625581,0.22774992,-0.22774992,0.625581,6.6459276,2.9316306)"
+     style="stroke-width:1.50207">
+    <path
+       inkscape:connector-curvature="0"
+       d="m -1.1859356,8.0378199 c -0.1104384,1.1352791 0.60859818,1.941859 1.61593659,1.831088 L 7.9646425,9.2204517 8.8554893,11.709436 11.085942,11.398158 10.041742,8.9747891 12.647291,8.6938208 11.86024,6.6550523 9.2159925,7.0530498 6.0102511,0.20363107 C 5.6024626,-0.72404869 4.5444759,-0.9435496 3.6164643,-0.28018086 L 7.1154601,7.2852992 Z"
+       id="path12477"
+       style="stroke-width:1.50207" />
+    <path
+       d="m 10.928696,5.0545541 c -0.828428,1.4348802 -0.142947,3.3815712 1.531071,4.3480657 1.674017,0.9664942 3.702642,0.5867935 4.53107,-0.8480868 0.82843,-1.43488 0.142946,-3.3815717 -1.53107,-4.3480657 -1.674018,-0.9664945 -3.702643,-0.5867936 -4.531071,0.8480868 z m 1.73204,0.999994 c 0.35503,-0.6149273 1.224823,-0.7774629 1.941888,-0.3634653 0.71793,0.4144973 1.011202,1.248529 0.656173,1.8634563 C 14.903769,8.1694665 14.034841,8.3325022 13.31691,7.9180046 12.599845,7.504007 12.305708,6.6694755 12.660736,6.0545481 Z"
+       id="path61250"
+       inkscape:connector-curvature="0"
+       style="stroke-width:1.50207" />
+    <path
+       id="path61253"
+       d="m 6.9286961,11.982758 c -0.8284285,1.43488 -0.1429467,3.381571 1.5310709,4.348066 1.674017,0.966494 3.702642,0.586793 4.531071,-0.848088 0.828428,-1.43488 0.142946,-3.381571 -1.531071,-4.348066 -1.6740176,-0.966494 -3.7026424,-0.586793 -4.5310709,0.848088 z m 1.7320405,0.999994 c 0.3550285,-0.614928 1.2248222,-0.777463 1.9418874,-0.363466 0.717931,0.414497 1.011202,1.248529 0.656173,1.863456 C 10.903769,15.09767 10.03484,15.260705 9.3169104,14.846208 8.5998452,14.432211 8.3057082,13.597679 8.6607366,12.982752 Z"
+       inkscape:connector-curvature="0"
+       style="stroke-width:1.50207" />
+  </g>
+  <g
+     aria-label="12"
+     id="text1445"
+     style="fill:#000000;stroke-width:0.977807"
+     transform="matrix(1.0226962,0,0,1.0226962,-0.18044148,-1.1812468)">
+    <path
+       d="m 0.67883548,3.1089373 q 0.30062665,0 0.58455212,-0.050104 Q 1.5473128,3.0087285 1.7727828,2.8918181 2.0066035,2.7749077 2.1652676,2.5911914 2.3322824,2.4074751 2.3823868,2.1402514 H 3.1590057 V 7.9857697 H 2.1151632 V 3.860504 H 0.67883548 Z"
+       id="path1647"
+       style="fill:#000000;stroke-width:0.977807" />
+    <path
+       d="M 7.9797421,7.9857697 H 3.9880881 Q 3.9964389,7.2592553 4.3388192,6.7164572 4.6811996,6.1736591 5.2741022,5.7728235 5.5580273,5.564055 5.8670047,5.371988 6.1759821,5.1715702 6.4348551,4.9461002 6.693728,4.7206302 6.8607428,4.4617573 7.0277576,4.1945336 7.0361084,3.8521532 q 0,-0.158664 -0.041754,-0.3340296 Q 6.9609517,3.3344073 6.8523921,3.184094 6.7438325,3.0254299 6.5517654,2.925221 6.3596984,2.8166614 6.050721,2.8166614 q -0.2839252,0 -0.4759922,0.1169104 Q 5.3910125,3.0421314 5.2741022,3.2425492 5.1655425,3.4346162 5.1070873,3.7018399 5.0569829,3.9690636 5.0486322,4.278041 H 4.0966478 q 0,-0.4843429 0.1252611,-0.8935292 Q 4.3555207,2.9669747 4.6143937,2.6663481 4.8732666,2.3657214 5.2406992,2.1987066 5.6164825,2.0233411 6.1091762,2.0233411 q 0.5344474,0 0.8935292,0.1753655 0.3590819,0.1753656 0.5762011,0.4425893 0.22547,0.2672237 0.3173282,0.5845518 0.091858,0.3089774 0.091858,0.5929026 0,0.3507311 -0.1085596,0.6346562 Q 7.7709735,4.7373317 7.5872573,4.9795032 7.403541,5.2133239 7.1697202,5.4137417 6.9358995,5.6141595 6.6853773,5.789525 6.4348551,5.9648906 6.1843329,6.1235546 5.9338107,6.2822187 5.7166914,6.4408828 5.5079229,6.5995468 5.3492588,6.7749124 5.1905948,6.9419272 5.1321396,7.1339942 h 2.8476025 z"
+       id="path1649"
+       style="fill:#000000;stroke-width:0.977807" />
+  </g>
+</svg>
diff --git a/share/ui/CMakeLists.txt b/share/ui/CMakeLists.txt
index 4e1843894d..2a4627b68b 100644
--- a/share/ui/CMakeLists.txt
+++ b/share/ui/CMakeLists.txt
@@ -1,6 +1,9 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
-file(GLOB _FILES "*.xml" "*.rc" "*.css" "*.ui" "*.glade" "*.svg" "*.ini")
+file(GLOB _FILES "*.xml" "*.rc" "*.css" "*.ui" "*.glade" "*.svg" "*.ini" "*.lang")
 install(FILES ${_FILES} DESTINATION ${INKSCAPE_SHARE_INSTALL}/ui)
 
 file(GLOB _RESOURCES "resources/*.png" "resources/*.svg")
 install(FILES ${_RESOURCES} DESTINATION ${INKSCAPE_SHARE_INSTALL}/ui/resources)
+
+file(GLOB _SYNTAX_THEMES "syntax-themes/*.xml")
+install(FILES ${_SYNTAX_THEMES} DESTINATION ${INKSCAPE_SHARE_INSTALL}/ui/syntax-themes)
diff --git a/share/ui/attribute-edit-component.glade b/share/ui/attribute-edit-component.glade
new file mode 100644
index 0000000000..e4537d611a
--- /dev/null
+++ b/share/ui/attribute-edit-component.glade
@@ -0,0 +1,335 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!-- Generated with glade 3.40.0 -->
+<interface>
+  <requires lib="gtk+" version="3.24"/>
+  <!-- interface-css-provider-path style.css -->
+  <object class="GtkImage" id="image1">
+    <property name="visible">True</property>
+    <property name="can-focus">False</property>
+    <property name="icon-name">rounding</property>
+  </object>
+  <object class="GtkBox" id="main-box">
+    <property name="visible">True</property>
+    <property name="can-focus">False</property>
+    <property name="orientation">vertical</property>
+    <child>
+      <object class="GtkScrolledWindow" id="scrolled-wnd">
+        <property name="visible">True</property>
+        <property name="can-focus">True</property>
+        <property name="shadow-type">in</property>
+        <child>
+          <object class="GtkTreeView" id="tree-view">
+            <property name="visible">True</property>
+            <property name="can-focus">False</property>
+            <property name="headers-clickable">False</property>
+            <property name="enable-search">False</property>
+            <property name="hover-selection">True</property>
+            <property name="activate-on-single-click">True</property>
+            <child internal-child="selection">
+              <object class="GtkTreeSelection"/>
+            </child>
+          </object>
+        </child>
+      </object>
+      <packing>
+        <property name="expand">True</property>
+        <property name="fill">True</property>
+        <property name="position">0</property>
+      </packing>
+    </child>
+    <child>
+      <object class="GtkScrolledWindow" id="content-sw">
+        <property name="can-focus">True</property>
+        <property name="no-show-all">True</property>
+        <property name="shadow-type">in</property>
+        <child>
+          <placeholder/>
+        </child>
+        <style>
+          <class name="mono-font"/>
+        </style>
+      </object>
+      <packing>
+        <property name="expand">True</property>
+        <property name="fill">True</property>
+        <property name="position">1</property>
+      </packing>
+    </child>
+    <child>
+      <object class="GtkBox" id="status-box">
+        <property name="visible">True</property>
+        <property name="can-focus">False</property>
+        <child>
+          <object class="GtkLabel" id="status-label">
+            <property name="width-request">1</property>
+            <property name="visible">True</property>
+            <property name="can-focus">False</property>
+            <property name="halign">start</property>
+            <property name="valign">center</property>
+            <property name="use-markup">True</property>
+            <property name="wrap">True</property>
+            <style>
+              <class name="small-font"/>
+            </style>
+          </object>
+          <packing>
+            <property name="expand">True</property>
+            <property name="fill">True</property>
+            <property name="position">0</property>
+          </packing>
+        </child>
+      </object>
+      <packing>
+        <property name="expand">False</property>
+        <property name="fill">True</property>
+        <property name="padding">2</property>
+        <property name="pack-type">end</property>
+        <property name="position">2</property>
+      </packing>
+    </child>
+  </object>
+  <object class="GtkMenu" id="menu1">
+    <property name="visible">True</property>
+    <property name="can-focus">False</property>
+    <property name="reserve-toggle-size">False</property>
+    <child>
+      <object class="GtkMenuItem" id="_0">
+        <property name="visible">True</property>
+        <property name="can-focus">False</property>
+        <property name="label" translatable="yes">N</property>
+        <property name="use-underline">True</property>
+      </object>
+    </child>
+    <child>
+      <object class="GtkMenuItem" id="_1">
+        <property name="visible">True</property>
+        <property name="can-focus">False</property>
+        <property name="label" translatable="yes">N.N</property>
+        <property name="use-underline">True</property>
+      </object>
+    </child>
+    <child>
+      <object class="GtkMenuItem" id="_2">
+        <property name="visible">True</property>
+        <property name="can-focus">False</property>
+        <property name="label" translatable="yes">N.NN</property>
+        <property name="use-underline">True</property>
+      </object>
+    </child>
+    <child>
+      <object class="GtkMenuItem" id="_3">
+        <property name="visible">True</property>
+        <property name="can-focus">False</property>
+        <property name="label" translatable="yes">N.NNN</property>
+        <property name="use-underline">True</property>
+      </object>
+    </child>
+    <child>
+      <object class="GtkMenuItem" id="_4">
+        <property name="visible">True</property>
+        <property name="can-focus">False</property>
+        <property name="label" translatable="yes">N.NNNN</property>
+        <property name="use-underline">True</property>
+      </object>
+    </child>
+    <child>
+      <object class="GtkMenuItem" id="_5">
+        <property name="visible">True</property>
+        <property name="can-focus">False</property>
+        <property name="label" translatable="yes">N.NNNNN</property>
+        <property name="use-underline">True</property>
+      </object>
+    </child>
+  </object>
+  <object class="GtkPopover" id="popup">
+    <property name="can-focus">False</property>
+    <property name="relative-to">tree-view</property>
+    <property name="position">bottom</property>
+    <child>
+      <object class="GtkBox">
+        <property name="visible">True</property>
+        <property name="can-focus">False</property>
+        <property name="orientation">vertical</property>
+        <child>
+          <object class="GtkScrolledWindow" id="scroll-wnd">
+            <property name="visible">True</property>
+            <property name="can-focus">True</property>
+            <property name="margin-start">3</property>
+            <property name="margin-end">3</property>
+            <property name="margin-top">3</property>
+            <property name="margin-bottom">4</property>
+            <property name="vexpand">True</property>
+            <property name="propagate-natural-width">True</property>
+            <child>
+              <placeholder/>
+            </child>
+            <style>
+              <class name="mono-font"/>
+            </style>
+          </object>
+          <packing>
+            <property name="expand">False</property>
+            <property name="fill">True</property>
+            <property name="position">0</property>
+          </packing>
+        </child>
+        <child>
+          <object class="GtkBox">
+            <property name="visible">True</property>
+            <property name="can-focus">False</property>
+            <property name="margin-start">5</property>
+            <property name="margin-end">5</property>
+            <property name="margin-bottom">4</property>
+            <property name="spacing">6</property>
+            <child type="center">
+              <object class="GtkBox" id="rounding-box">
+                <property name="visible">True</property>
+                <property name="can-focus">False</property>
+                <property name="margin-end">5</property>
+                <child>
+                  <object class="GtkButton" id="btn-truncate">
+                    <property name="visible">True</property>
+                    <property name="can-focus">True</property>
+                    <property name="receives-default">True</property>
+                    <property name="tooltip-text" translatable="yes">Round selected numbers to N digits</property>
+                    <property name="image">image1</property>
+                    <property name="use-underline">True</property>
+                  </object>
+                  <packing>
+                    <property name="expand">False</property>
+                    <property name="fill">True</property>
+                    <property name="position">0</property>
+                  </packing>
+                </child>
+                <child>
+                  <object class="GtkMenuButton" id="btn-menu">
+                    <property name="visible">True</property>
+                    <property name="can-focus">True</property>
+                    <property name="focus-on-click">False</property>
+                    <property name="receives-default">True</property>
+                    <property name="margin-start">2</property>
+                    <property name="relief">none</property>
+                    <property name="popup">menu1</property>
+                    <child>
+                      <object class="GtkBox">
+                        <property name="visible">True</property>
+                        <property name="can-focus">False</property>
+                        <child>
+                          <object class="GtkLabel" id="precision">
+                            <property name="visible">True</property>
+                            <property name="can-focus">False</property>
+                            <property name="label" translatable="yes">N.NNNNN</property>
+                          </object>
+                          <packing>
+                            <property name="expand">False</property>
+                            <property name="fill">True</property>
+                            <property name="position">0</property>
+                          </packing>
+                        </child>
+                        <child>
+                          <object class="GtkImage">
+                            <property name="visible">True</property>
+                            <property name="can-focus">False</property>
+                            <property name="icon-name">pan-down-symbolic</property>
+                          </object>
+                          <packing>
+                            <property name="expand">False</property>
+                            <property name="fill">True</property>
+                            <property name="position">1</property>
+                          </packing>
+                        </child>
+                      </object>
+                    </child>
+                    <style>
+                      <class name="menu-btn-tight"/>
+                    </style>
+                  </object>
+                  <packing>
+                    <property name="expand">False</property>
+                    <property name="fill">True</property>
+                    <property name="position">1</property>
+                  </packing>
+                </child>
+              </object>
+              <packing>
+                <property name="expand">False</property>
+                <property name="fill">True</property>
+                <property name="position">9</property>
+              </packing>
+            </child>
+            <child>
+              <object class="GtkLabel" id="help">
+                <property name="visible">True</property>
+                <property name="can-focus">False</property>
+                <property name="label" translatable="yes">Shift+Return to close</property>
+                <property name="justify">center</property>
+                <property name="wrap">True</property>
+                <property name="max-width-chars">2</property>
+                <property name="yalign">0.5</property>
+              </object>
+              <packing>
+                <property name="expand">False</property>
+                <property name="fill">True</property>
+                <property name="position">0</property>
+              </packing>
+            </child>
+            <child>
+              <object class="GtkButton" id="btn-ok">
+                <property name="label" translatable="yes">OK</property>
+                <property name="visible">True</property>
+                <property name="can-focus">True</property>
+                <property name="receives-default">True</property>
+                <property name="use-underline">True</property>
+              </object>
+              <packing>
+                <property name="expand">False</property>
+                <property name="fill">True</property>
+                <property name="pack-type">end</property>
+                <property name="position">1</property>
+              </packing>
+            </child>
+            <child>
+              <object class="GtkButton" id="btn-cancel">
+                <property name="label" translatable="yes">Cancel</property>
+                <property name="visible">True</property>
+                <property name="can-focus">True</property>
+                <property name="receives-default">True</property>
+                <property name="use-underline">True</property>
+              </object>
+              <packing>
+                <property name="expand">False</property>
+                <property name="fill">True</property>
+                <property name="pack-type">end</property>
+                <property name="position">2</property>
+              </packing>
+            </child>
+            <style>
+              <class name="small-font"/>
+            </style>
+          </object>
+          <packing>
+            <property name="expand">False</property>
+            <property name="fill">True</property>
+            <property name="position">1</property>
+          </packing>
+        </child>
+      </object>
+    </child>
+  </object>
+  <object class="GtkSizeGroup">
+    <widgets>
+      <widget name="btn-cancel"/>
+      <widget name="btn-ok"/>
+    </widgets>
+  </object>
+  <object class="GtkListStore" id="store">
+    <columns>
+      <!-- column-name attr-name -->
+      <column type="gchararray"/>
+      <!-- column-name attr-value -->
+      <column type="gchararray"/>
+      <!-- column-name attr-value-renderer -->
+      <column type="gchararray"/>
+    </columns>
+  </object>
+</interface>
diff --git a/share/ui/inline-css.lang b/share/ui/inline-css.lang
new file mode 100644
index 0000000000..29a04df247
--- /dev/null
+++ b/share/ui/inline-css.lang
@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<language id="inline-css" _name="Inline CSS" version="2.0" _section="Markup">
+  <definitions>
+    <context id="inline-css">
+      <include>
+        <context ref="css:style-block-content"/>
+      </include>
+    </context>
+  </definitions>
+</language>
diff --git a/share/ui/style.css b/share/ui/style.css
index b19b8078b8..45c04cab7d 100644
--- a/share/ui/style.css
+++ b/share/ui/style.css
@@ -168,9 +168,8 @@ notebook.blink > header > tabs > tab:checked {
     color: inherit;
 }
 
-/* attribute dialog popup size */
-.attrpop textview {
-    font-size: 13px;
+.mono-font {
+    /* note: monospaced font is set by ThemeContext::adjust_global_font_scale() */
 }
 
 /* 
@@ -225,12 +224,12 @@ iconview *:hover {
 }
 
 .menu-category {
-    font-size: small;
+    font-size: smaller;
     font-weight: bold;
 }
 
 .small-heading {
-    font-size: small;
+    font-size: smaller;
     font-weight: bold;
     opacity: 0.5;
 }
@@ -250,7 +249,7 @@ iconview *:hover {
 }
 
 
-/* Selector and XML dialog */
+/* Selector dialog */
 #SelectorsAndStyleDialog button {
     padding: 4px;
     min-height: 16px;
@@ -266,14 +265,12 @@ iconview *:hover {
     padding-bottom: 0;
 }
 
-#XMLAndAttributesDialog .radio.image-button,
 #SelectorsAndStyleDialog .radio.image-button {
     margin: 0;
     padding: 0px;
     border-radius: 2px 0 0 2px;
 }
 
-#XMLAndAttributesDialog .radio.image-button:last-child,
 #SelectorsAndStyleDialog .radio.image-button:last-child {
     border-radius: 0 2px 2px 0;
     border-left-width: 0;
@@ -455,7 +452,7 @@ SPCanvas {
 #Objects .search {
   padding: 2px 4px;
   min-height: 16px;
-  font-size: small;
+  font-size: smaller;
 }
 
 #SimpleFilterModifier #InkSpinScale {
@@ -595,7 +592,7 @@ scale.tight-slider {
 
 /* add .small-marks class to Gtk::Scale to have smaller font used, since markup didn't work there */
 scale.small-marks.marks-after {
-    font-size: small;
+    font-size: smaller;
 }
 
 /* Square toolbar buttons: request square buttons for all toolbars. */
@@ -617,7 +614,7 @@ button.square-button image {
 }
 
 #StyleSwatch label {
-    font-size: small;
+    font-size: smaller;
 }
 
 #DocumentProperties #NotebookPage {
@@ -646,7 +643,7 @@ button.square-button image {
 }
 
 .small-font {
-    font-size: small;
+    font-size: smaller;
 }
 
 .toolbar-separator {
diff --git a/share/ui/svgd.lang b/share/ui/svgd.lang
new file mode 100644
index 0000000000..0c86bd8b66
--- /dev/null
+++ b/share/ui/svgd.lang
@@ -0,0 +1,229 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+ This file is part of Inkscape.
+
+ Authors:
+   Rafael Siejakowski <rs@rs-math.net>
+
+ Copyright (C) 2022 the Authors.
+
+ Released under GNU GPL v2+, read the file 'COPYING' for more information.
+-->
+<language id="svgd" _name="SVG path attribute 'd'" version="2.0" _section="Markup">
+  <styles>
+    <style id="command" _name="Path command" map-to="def:keyword"/>
+    <style id="error" _name="Error" map-to="def:error"/>
+    <style id="numeric" _name="Path node coordinate" map-to="def:number"/>
+    <style id="alternate-numeric" _name="Control point coordinate" map-to="def:special-constant"/>
+    <style id="angle" _name="Ellipse rotation angle" map-to="def:type"/>
+    <style id="flags" _name="Boolean flags" map-to="def:preprocessor"/>
+  </styles>
+
+  <default-regex-options case-sensitive="false"/>
+
+  <definitions>
+    <!-- Based on SVG2 specification, § 9.3.9. The grammar for path data. -->
+
+    <define-regex id="maybecwsp">(?m)[\s,\r\n]*</define-regex>
+    <define-regex id="exponent">e[+\-]?\d+</define-regex>
+    <define-regex id="fractional-constant">\d*\.\d+|\d+</define-regex>
+    <define-regex id="number">\%{fractional-constant}(\%{exponent})?</define-regex>
+    <define-regex id="coordinate">[+\-]?\%{number}</define-regex>
+    <define-regex id="positive-coordinate">\+?\%{number}</define-regex>
+    <define-regex id="command-letter">[MLHVCSQTAZ]</define-regex>
+    <define-regex id="invalid">[^\-+\s\r\n,\.MLHVCSQTAZmlhvcsqtaz0-9]</define-regex>
+    <define-regex id="command-end">(?m)(?=\%{command-letter}|\%{invalid})</define-regex>
+
+    <!-- Define error contexts -->
+    <context id="command-not-allowed" style-ref="error" extend-parent="false" end-parent="true">
+      <match>\%{command-letter}</match>
+    </context>
+
+    <context id="invalid-char" style-ref="error" extend-parent="false" end-parent="true">
+      <match>\%{invalid}</match>
+    </context>
+
+    <!-- Coordinate pair is defined as a region (allows for two numbers on separate lines). -->
+    <context id="point">
+      <start>\%{coordinate}</start>
+      <end>\%{coordinate}</end>
+      <include>
+        <context ref="command-not-allowed"/>
+        <context ref="invalid-char"/>
+        <context sub-pattern="0" where="start" style-ref="numeric"/>
+        <context sub-pattern="0" where="end" style-ref="numeric"/>
+      </include>
+    </context>
+
+    <!-- PRIVATE: A pair of numbers with different highlighting. -->
+    <context id="PRIVATE-heterochromic4-inner2" extend-parent="true" once-only="true">
+      <start>\%{coordinate}</start>
+      <end>\%{coordinate}</end>
+      <include>
+        <context ref="command-not-allowed"/>
+        <context ref="invalid-char"/>
+        <context sub-pattern="0" where="start" style-ref="alternate-numeric"/>
+        <context sub-pattern="0" where="end" style-ref="numeric"/>
+      </include>
+    </context>
+
+    <!-- A 4-tuple of numbers with different highlighting for the first two than for the last two. -->
+    <context id="heterochromic4" extend-parent="false">
+      <start>\%{coordinate}</start>
+      <end>\%{coordinate}</end>
+      <include>
+        <context ref="command-not-allowed"/>
+        <context ref="invalid-char"/>
+        <context id="heterochromic4-first" sub-pattern="0" where="start" style-ref="alternate-numeric"/>
+        <context id="heterochromic4-last" sub-pattern="0" where="end" style-ref="numeric"/>
+        <context ref="PRIVATE-heterochromic4-inner2"/>
+      </include>
+    </context>
+
+    <!-- PRIVATE: A pair of numbers with alternate highlighting. -->
+    <context id="PRIVATE-heterochromic6-inner4-inner2" extend-parent="true" once-only="true">
+      <start>\%{coordinate}</start>
+      <end>\%{coordinate}</end>
+      <include>
+        <context ref="command-not-allowed"/>
+        <context ref="invalid-char"/>
+        <context sub-pattern="0" where="start" style-ref="alternate-numeric"/>
+        <context sub-pattern="0" where="end" style-ref="alternate-numeric"/>
+      </include>
+    </context>
+
+    <!-- PRIVATE: A 4-tuple of numbers with different highlighting for the first three than for the last one. -->
+    <context id="PRIVATE-heterochromic6-inner4" extend-parent="true" once-only="true">
+      <start>\%{coordinate}</start>
+      <end>\%{coordinate}</end>
+      <include>
+        <context ref="command-not-allowed"/>
+        <context ref="invalid-char"/>
+        <context sub-pattern="0" where="start" style-ref="alternate-numeric"/>
+        <context sub-pattern="0" where="end" style-ref="numeric"/>
+        <context ref="PRIVATE-heterochromic6-inner4-inner2"/>
+      </include>
+    </context>
+
+    <!-- A 6-tuple of numbers with different highlighting for the first four than for the last two. -->
+    <context id="heterochromic6" extend-parent="false">
+      <start>\%{coordinate}</start>
+      <end>\%{coordinate}</end>
+      <include>
+        <context ref="command-not-allowed"/>
+        <context ref="invalid-char"/>
+        <context sub-pattern="0" where="start" style-ref="alternate-numeric"/>
+        <context sub-pattern="0" where="end" style-ref="numeric"/>
+        <context ref="PRIVATE-heterochromic6-inner4"/>
+      </include>
+    </context>
+
+    <!-- PRIVATE: The third shell of arcto arguments. -->
+    <context id="PRIVATE-arcto-shell3" extend-parent="true" once-only="true">
+      <start>\%{coordinate}</start><!-- rotation angle -->
+      <end>(0|1)\%{maybecwsp}(0|1)</end><!-- flags -->
+      <include>
+        <context ref="command-not-allowed"/>
+        <context ref="invalid-char"/>
+        <context sub-pattern="0" where="start" style-ref="angle"/>
+        <context sub-pattern="0" where="end" style-ref="flags"/>
+      </include>
+    </context>
+
+    <!-- PRIVATE: The second shell of arcto arguments. -->
+    <context id="PRIVATE-arcto-shell2" extend-parent="true" once-only="true">
+      <start>\%{positive-coordinate}</start><!-- ray y -->
+      <end>\%{coordinate}</end><!-- endpoint x -->
+      <include>
+        <context ref="command-not-allowed"/>
+        <context ref="invalid-char"/>
+        <context sub-pattern="0" where="start" style-ref="alternate-numeric"/>
+        <context sub-pattern="0" where="end" style-ref="numeric"/>
+        <context ref="PRIVATE-arcto-shell3"/>
+      </include>
+    </context>
+
+    <!-- The arguments of an arcto command. -->
+    <context id="arcto-args" extend-parent="false">
+      <start>\%{positive-coordinate}</start><!-- ray x -->
+      <end>\%{coordinate}</end><!-- endpoint y -->
+      <include>
+        <context ref="command-not-allowed"/>
+        <context ref="invalid-char"/>
+        <context sub-pattern="0" where="start" style-ref="alternate-numeric"/>
+        <context sub-pattern="0" where="end" style-ref="numeric"/>
+        <context ref="PRIVATE-arcto-shell2"/>
+      </include>
+    </context>
+
+    <!-- A valid SVG coordinate. -->
+    <context id="coord" style-ref="numeric">
+      <match>\%{coordinate}</match>
+    </context>
+
+    <!-- Start the SVG path `d` definition. -->
+    <context id="svgd">
+      <include>
+
+        <!-- An M, L or T command (expecting a sequence of points). -->
+        <context id="moveto">
+          <start>M|L|T</start>
+          <end>\%{command-end}</end>
+          <include>
+            <context sub-pattern="0" where="start" style-ref="command"/>
+            <context ref="point"/>
+          </include>
+        </context>
+
+        <!-- An H or V command (expecting a sequence of coordinates). -->
+        <context id="paraxial">
+          <start>H|V</start>
+          <end>\%{command-end}</end>
+          <include>
+            <context sub-pattern="0" where="start" style-ref="command"/>
+            <context ref="coord"/>
+          </include>
+        </context>
+
+        <!-- S and Q commands: expecting a sequence of **pairs** of points. -->
+        <context id="smooth-cubic-or-quadratic">
+          <start>S|Q</start>
+          <end>\%{command-end}</end>
+          <include>
+            <context sub-pattern="0" where="start" style-ref="command"/>
+            <!-- The argument of the S/Q command is 4*n numbers; in each 4-tuple we
+                 highlight the first two coords differently than the last two. -->
+            <context ref="heterochromic4"/>
+          </include>
+        </context>
+
+        <!-- C command: expecting a sequence of **triples** of points. -->
+        <context id="cubic-bezier">
+          <start>C</start>
+          <end>\%{command-end}</end>
+          <include>
+            <context sub-pattern="0" where="start" style-ref="command"/>
+            <!-- In each 6-tuple we highlight the first four numbers differently than the last two. -->
+            <context ref="heterochromic6"/>
+          </include>
+        </context>
+
+        <!-- A command: elliptical arc. -->
+        <context id="elliptical-arc">
+          <start>A</start>
+          <end>\%{command-end}</end>
+          <include>
+            <context sub-pattern="0" where="start" style-ref="command"/>
+            <context ref="arcto-args"/>
+          </include>
+        </context>
+
+        <context id="z-command" style-ref="command">
+          <keyword>Z</keyword>
+        </context>
+
+        <context ref="invalid-char"/>
+      </include>
+    </context>
+  </definitions>
+</language>
diff --git a/share/ui/svgpoints.lang b/share/ui/svgpoints.lang
new file mode 100644
index 0000000000..f341af66e9
--- /dev/null
+++ b/share/ui/svgpoints.lang
@@ -0,0 +1,47 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+ This file is part of Inkscape.
+
+ Authors:
+   Rafael Siejakowski <rs@rs-math.net>
+
+ Copyright (C) 2022 the Authors.
+
+ Released under GNU GPL v2+, read the file 'COPYING' for more information.
+-->
+<language id="svgpoints" _name="SVG attribute 'points' of polygon and polyline elements" version="2.0" _section="Markup">
+  <styles>
+    <style id="error" _name="Error" map-to="def:error"/>
+    <style id="numeric" _name="Vertex coordinate" map-to="def:number"/>
+  </styles>
+
+  <definitions>
+    <define-regex id="exponent">e[+\-]?\d+</define-regex>
+    <define-regex id="fractional-constant">\d*\.\d+|\d+</define-regex>
+    <define-regex id="number">\%{fractional-constant}(\%{exponent})?</define-regex>
+    <define-regex id="coordinate">[+\-]?\%{number}</define-regex>
+    <define-regex id="invalid">[^\-+\s\r\n,\.0-9eE]</define-regex>
+
+    <!-- Invalid character (not allowed in the 'points' attribute). -->
+    <context id="invalid-char" style-ref="error" extend-parent="false" end-parent="true">
+      <match>\%{invalid}</match>
+    </context>
+
+    <!-- The 'points' attribute. -->
+    <context id="svgpoints">
+      <include>
+        <!-- Coordinate pair is defined as a region (allows for two numbers on separate lines). -->
+        <context id="point">
+          <start>\%{coordinate}</start>
+          <end>\%{coordinate}</end>
+          <include>
+            <context ref="invalid-char"/>
+            <context sub-pattern="0" where="start" style-ref="numeric"/>
+            <context sub-pattern="0" where="end" style-ref="numeric"/>
+          </include>
+        </context>
+        <context ref="invalid-char"/>
+      </include>
+    </context>
+  </definitions>
+</language>
diff --git a/share/ui/syntax-themes/syntax-theme-dark.xml b/share/ui/syntax-themes/syntax-theme-dark.xml
new file mode 100644
index 0000000000..74ddf0b370
--- /dev/null
+++ b/share/ui/syntax-themes/syntax-theme-dark.xml
@@ -0,0 +1,77 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+ This file is part of Inkscape.
+
+ Copyright (C) 2022 the Authors.
+
+ Released under GNU GPL v2+, read the file 'COPYING' for more information.
+-->
+
+<style-scheme id="inkscape-dark" _name="Inkscape Dark" version="1.0">
+
+  <author>MK</author>
+  <_description>Dark color scheme for syntax highlighting</_description>
+
+  <color name="green"                       value="#a6e22e"/>
+  <color name="purple"                      value="#af83f8"/>
+  <color name="yellow"                      value="#f2d375"/>
+  <color name="cyan"                        value="#87dbe8"/>
+  <color name="pale-yellow"                 value="#795b07"/>
+  <color name="pale-red"                    value="#96242f"/>
+  <color name="orange"                      value="#ee9d70"/>
+  <color name="selection"                   value="#094bac"/>
+  <color name="white"                       value="#f0f0f0"/>
+  <color name="blue"                        value="#6d9eeb"/>
+  <color name="gray"                        value="#7f7f7f"/>
+  <color name="red"                         value="#f98691"/>
+
+  <!-- Global Settings -->
+  <style name="text"                        foreground="white" />
+  <style name="selection"                   foreground="white" background="selection"/>
+  <style name="cursor"                      foreground="white" bold="true" />
+  <style name="secondary-cursor"            foreground="white" bold="true" />
+  <style name="line-numbers"                foreground="gray"/>
+  <style name="draw-spaces"                 foreground="gray"/>
+  <style name="background-pattern" />
+  <style name="current-line" />
+
+  <!-- Bracket Matching -->
+  <style name="bracket-match"               foreground="red"/>
+  <style name="bracket-mismatch"            foreground="purple" background="pale-yellow"/>
+
+  <!-- Search Matching -->
+  <style name="search-match"                foreground="white" background="pale-yellow"/>
+
+  <!-- Comments -->
+  <style name="def:comment"                 foreground="orange"/>
+
+  <!-- Constants -->
+  <style name="def:constant"                foreground="cyan"/>
+  <style name="def:string"                  foreground="yellow"/>
+  <style name="def:special-char"            foreground="red"/>
+  <style name="def:special-constant"        foreground="cyan"/>
+  <style name="def:number"                  foreground="red"/>
+  <style name="def:decimal"                 foreground="red"/>
+  <style name="def:floating-point"          foreground="red"/>
+
+  <!-- Identifiers -->
+  <style name="def:identifier"              foreground="green"/>
+  <style name="def:keyword"                 foreground="blue" bold="true"/>
+  <style name="def:function"                foreground="purple" bold="false"/>
+
+  <!-- Statements -->
+  <style name="def:statement"               foreground="blue" bold="false"/>
+
+  <!-- Types -->
+  <style name="def:type"                    foreground="yellow" bold="false"/>
+
+  <!-- Others -->
+  <style name="css:delimiter"               foreground="gray"/>
+  <style name="def:complex"                 foreground="green"/>
+  <style name="def:preprocessor"            foreground="green"/>
+  <style name="def:error"                   foreground="white" background="pale-red" bold="false"/>
+  <style name="def:warning"                 foreground="white" background="pale-yellow"/>
+  <style name="def:note"                    foreground="gray" bold="false"/>
+  <style name="def:underlined"              italic="true" underline="single"/>
+
+</style-scheme>
diff --git a/share/ui/syntax-themes/syntax-theme-light.xml b/share/ui/syntax-themes/syntax-theme-light.xml
new file mode 100644
index 0000000000..78e6ae1414
--- /dev/null
+++ b/share/ui/syntax-themes/syntax-theme-light.xml
@@ -0,0 +1,79 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+ This file is part of Inkscape.
+
+ Copyright (C) 2022 the Authors.
+
+ Released under GNU GPL v2+, read the file 'COPYING' for more information.
+-->
+
+<style-scheme id="inkscape-light" _name="Inkscape Light" version="1.0">
+
+  <author>MK</author>
+  <_description>Light color scheme for syntax highlighting</_description>
+
+  <color name="green"                       value="#1E8806"/>
+  <color name="purple"                      value="#6321cf"/>
+  <color name="yellow"                      value="#ae8305"/>
+  <color name="cyan"                        value="#038387"/>
+  <color name="pale-yellow"                 value="#ffe9a6"/>
+  <color name="pale-red"                    value="#f2b6bc"/>
+  <color name="orange"                      value="#de6502"/>
+  <color name="selection"                   value="#a8cbfe"/>
+  <color name="blue"                        value="#0b5cd5"/>
+  <color name="black"                       value="#000000"/>
+  <color name="gray"                        value="#a0a0a0"/>
+  <color name="red"                         value="#dc3545"/>
+  <color name="lime"                        value="#799E00"/>
+  <color name="brown"                       value="#a84a00"/>
+
+  <!-- Global Settings -->
+  <style name="text"                        foreground="black" />
+  <style name="selection"                   foreground="black" background="selection"/>
+  <style name="cursor"                      foreground="black" bold="true" />
+  <style name="secondary-cursor"            foreground="black" bold="true" />
+  <style name="line-numbers"                foreground="gray"/>
+  <style name="draw-spaces"                 foreground="gray"/>
+  <style name="background-pattern" />
+  <style name="current-line" />
+
+  <!-- Bracket Matching -->
+  <style name="bracket-match"               foreground="red"/>
+  <style name="bracket-mismatch"            foreground="purple" background="pale-yellow"/>
+
+  <!-- Search Matching -->
+  <style name="search-match"                foreground="black" background="pale-yellow"/>
+
+  <!-- Comments -->
+  <style name="def:comment"                 foreground="lime"/>
+
+  <!-- Constants -->
+  <style name="def:constant"                foreground="cyan"/>
+  <style name="def:string"                  foreground="yellow"/>
+  <style name="def:special-char"            foreground="brown"/>
+  <style name="def:special-constant"        foreground="cyan"/>
+  <style name="def:number"                  foreground="red"/>
+  <style name="def:decimal"                 foreground="red"/>
+  <style name="def:floating-point"          foreground="red"/>
+
+  <!-- Identifiers -->
+  <style name="def:identifier"              foreground="green"/>
+  <style name="def:keyword"                 foreground="blue" bold="true"/>
+  <style name="def:function"                foreground="purple" bold="false"/>
+
+  <!-- Statements -->
+  <style name="def:statement"               foreground="blue" bold="false"/>
+
+  <!-- Types -->
+  <style name="def:type"                    foreground="orange" bold="false"/>
+
+  <!-- Others -->
+  <style name="css:delimiter"               foreground="gray"/>
+  <style name="def:complex"                 foreground="purple"/>
+  <style name="def:preprocessor"            foreground="purple"/>
+  <style name="def:error"                   foreground="black" background="pale-red" bold="false"/>
+  <style name="def:warning"                 foreground="black" background="pale-yellow"/>
+  <style name="def:note"                    foreground="gray" bold="false"/>
+  <style name="def:underlined"              italic="true" underline="single"/>
+
+</style-scheme>
diff --git a/share/ui/syntax-themes/syntax-theme-none.xml b/share/ui/syntax-themes/syntax-theme-none.xml
new file mode 100644
index 0000000000..307f032c32
--- /dev/null
+++ b/share/ui/syntax-themes/syntax-theme-none.xml
@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+ This file is part of Inkscape.
+
+ Copyright (C) 2022 the Authors.
+
+ Released under GNU GPL v2+, read the file 'COPYING' for more information.
+-->
+
+<style-scheme id="-none-" _name="&#x25cf; No coloring" version="1.0">
+
+  <author>MK</author>
+  <_description>Empty color scheme to disable syntax highlighting</_description>
+
+  <style name="text" />
+
+</style-scheme>
diff --git a/snap/snapcraft.yaml b/snap/snapcraft.yaml
index 8b5c0ef61e..d5b9d54364 100644
--- a/snap/snapcraft.yaml
+++ b/snap/snapcraft.yaml
@@ -48,6 +48,7 @@ parts:
       - libgspell-1-dev
       - libgtk-3-dev
       - libgtkmm-3.0-dev
+      - libgtksourceview-4-dev
       - libharfbuzz-dev
       - liblcms2-dev
       - libmagick++-dev
@@ -82,6 +83,8 @@ parts:
       - libgslcblas0
       - libgspell-1-2
       - libgtkmm-3.0-1v5
+      - libgtksourceview-4-common
+      - libgtksourceview-4-0
       - liblcms2-2
       - libmagick++-6.q16-8
       - libpangomm-1.4-1v5
diff --git a/src/attribute-rel-util.cpp b/src/attribute-rel-util.cpp
index f88cf8b449..4527aae42c 100644
--- a/src/attribute-rel-util.cpp
+++ b/src/attribute-rel-util.cpp
@@ -24,6 +24,9 @@
 #include <iostream>
 #include <sstream>
 
+#include <2geom/path-sink.h>
+#include <2geom/svg-path-parser.h>
+
 #include "attribute-rel-css.h"
 #include "attribute-rel-svg.h"
 #include "preferences.h"
@@ -330,6 +333,36 @@ bool sp_attribute_check_attribute(Glib::ustring const &element, Glib::ustring co
     return is_useful;
 }
 
+bool sp_is_valid_svg_path_d(Glib::ustring const &d)
+{
+    /** A PathSink going straight to /dev/null */
+    class PathBlackHole final : public Geom::PathSink
+    {
+        using Geom::PathSink::feed;
+        void moveTo(Geom::Point const &) final {}
+        void lineTo(Geom::Point const &) final {}
+        void curveTo(Geom::Point const &, Geom::Point const &, Geom::Point const &) final {}
+        void quadTo(Geom::Point const &, Geom::Point const &) final {}
+        void arcTo(Geom::Coord, Geom::Coord, Geom::Coord, bool, bool, Geom::Point const &) final {}
+        void closePath() final {}
+        void flush() final {}
+        void feed(Geom::Curve const &, bool) final {}
+        void feed(Geom::Path const &) final {}
+        void feed(Geom::PathVector const &) final {}
+        void feed(Geom::Rect const &) final {}
+        void feed(Geom::Circle const &) final {}
+        void feed(Geom::Ellipse const &) final {}
+    } dev_null;
+
+    auto validator = Geom::SVGPathParser(dev_null);
+    try {
+        validator.parse(static_cast<std::string>(d));
+    } catch (Geom::SVGPathParseError &) {
+        return false;
+    }
+    return true;
+}
+
 /*
   Local Variables:
   mode:c++
diff --git a/src/attribute-rel-util.h b/src/attribute-rel-util.h
index 3b4f327e9d..490c9bc5da 100644
--- a/src/attribute-rel-util.h
+++ b/src/attribute-rel-util.h
@@ -1,21 +1,16 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 /** @file
- * TODO: insert short description here
+ * Utility functions related to parsing and validation of XML attributes.
  *//*
- * Authors: see git history
+ * Authors:
+ *   tavmjong
  *
  * Copyright (C) 2016 Authors
- * Released under GNU GPL v2+, read the file 'COPYING' for more information.
- */
-#ifndef __SP_ATTRIBUTE_REL_UTIL_H__
-#define __SP_ATTRIBUTE_REL_UTIL_H__
-
-/*
- * attribute-rel-util.h
  *
- *  Created on: Sep 8, 2011
- *      Author: tavmjong
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
  */
+#ifndef SEEN_ATTRIBUTE_REL_UTIL_H
+#define SEEN_ATTRIBUTE_REL_UTIL_H
 
 #include <glibmm/ustring.h>
 
@@ -91,7 +86,15 @@ void sp_attribute_purge_default_style(SPCSSAttr *css, unsigned int flags);
 bool sp_attribute_check_attribute(Glib::ustring const &element, Glib::ustring const &id, Glib::ustring const &attribute,
                                   bool warn);
 
-#endif /* __SP_ATTRIBUTE_REL_UTIL_H__ */
+/**
+ * @brief Check whether the 'd' attribute on a <path> element parses correctly.
+ *
+ * @param d The value of the 'd' attribute.
+ * @return false if the value causes a parser error, true otherwise.
+ */
+bool sp_is_valid_svg_path_d(Glib::ustring const &d);
+
+#endif // SEEN_ATTRIBUTE_REL_UTIL_H
 
 /*
   Local Variables:
diff --git a/src/inkscape.cpp b/src/inkscape.cpp
index 6d1aefb2da..c35c78dce9 100644
--- a/src/inkscape.cpp
+++ b/src/inkscape.cpp
@@ -214,8 +214,9 @@ Application::Application(bool use_gui) :
         icon_theme->prepend_search_path(get_path_ustring(USER, ICONS));
         themecontext = new Inkscape::UI::ThemeContext();
         themecontext->add_gtk_css(false);
-        auto scale = prefs->getDoubleLimited("/theme/fontscale", 100, 50, 150);
-        themecontext->adjust_global_font_scale(scale / 100.0);
+        auto scale = prefs->getDoubleLimited(UI::ThemeContext::get_font_scale_pref_path(), 100, 50, 150);
+        themecontext->adjustGlobalFontScale(scale / 100.0);
+        Inkscape::UI::ThemeContext::initialize_source_syntax_styles();
         Inkscape::DeviceManager::getManager().loadConfig();
     }
 
@@ -272,6 +273,10 @@ Application::Application(bool use_gui) :
                     }
                 }
             }
+            // select default syntax coloring theme, if needed
+            if (auto desktop = active_desktop()) {
+                UI::ThemeContext::select_default_syntax_style(themecontext->isCurrentThemeDark(desktop->getToplevel()));
+            }
         });
     }
 
diff --git a/src/object/sp-factory.cpp b/src/object/sp-factory.cpp
index 4dc0d6605c..ddd9afcb2e 100644
--- a/src/object/sp-factory.cpp
+++ b/src/object/sp-factory.cpp
@@ -114,6 +114,17 @@ public:
         return it->second();
     }
 
+    bool supportsId(std::string const &id) const
+    {
+        return map.find(id) != map.end();
+    }
+
+    static Factory const &get()
+    {
+        static Factory const singleton;
+        return singleton;
+    }
+
 private:
     using Func = SPObject*(*)();
 
@@ -273,8 +284,12 @@ private:
 
 SPObject *SPFactory::createObject(std::string const &id)
 {
-    static Factory const factory;
-    return factory.create(id);
+    return Factory::get().create(id);
+}
+
+bool SPFactory::supportsType(std::string const &id)
+{
+    return Factory::get().supportsId(id);
 }
 
 std::string NodeTraits::get_type_string(Inkscape::XML::Node const &node)
diff --git a/src/object/sp-factory.h b/src/object/sp-factory.h
index 4db5891126..b8eba25fb6 100644
--- a/src/object/sp-factory.h
+++ b/src/object/sp-factory.h
@@ -24,6 +24,7 @@ class Node;
 
 struct SPFactory {
     static SPObject *createObject(std::string const &id);
+    static bool supportsType(std::string const &id);
 };
 
 struct NodeTraits {
diff --git a/src/preferences.h b/src/preferences.h
index 1ffb96916b..13bff80c00 100644
--- a/src/preferences.h
+++ b/src/preferences.h
@@ -897,6 +897,21 @@ private:
     auto changed(Preferences::Entry const &e) const { return e.getDoubleLimited(def, min, max); }
 };
 
+template<>
+class Pref<Glib::ustring> : public PrefBase<Glib::ustring>
+{
+public:
+    Pref(Glib::ustring path, Glib::ustring def = "")
+        : PrefBase(std::move(path), def)
+    {
+        init();
+    }
+private:
+    friend PrefBase;
+    auto read() const { return Preferences::get()->getString(observed_path, def); }
+    auto changed(Preferences::Entry const &e) const { return e.getString(def); }
+};
+
 template<>
 class Pref<void> : public Preferences::Observer
 {
diff --git a/src/ui/CMakeLists.txt b/src/ui/CMakeLists.txt
index fe6aada92d..0aaa4e12f2 100644
--- a/src/ui/CMakeLists.txt
+++ b/src/ui/CMakeLists.txt
@@ -16,6 +16,7 @@ set(ui_SRC
 	simple-pref-pusher.cpp
 	shortcuts.cpp
 	svg-renderer.cpp
+	syntax.cpp
 	themes.cpp
 	tool-factory.cpp
 	util.cpp
@@ -280,6 +281,7 @@ set(ui_SRC
 	shape-editor.h
 	simple-pref-pusher.h
 	shortcuts.h
+	syntax.h
 	themes.h
 	tool-factory.h
 	util.h
diff --git a/src/ui/dialog/attrdialog.cpp b/src/ui/dialog/attrdialog.cpp
index efd0895f0b..22d2bd7790 100644
--- a/src/ui/dialog/attrdialog.cpp
+++ b/src/ui/dialog/attrdialog.cpp
@@ -12,20 +12,53 @@
 
 #include "attrdialog.h"
 
+#include "preferences.h"
 #include "selection.h"
 #include "document-undo.h"
 #include "message-context.h"
 #include "message-stack.h"
 #include "style.h"
 
+#include "io/resource.h"
+
+#include "ui/builder-utils.h"
+#include "ui/dialog/inkscape-preferences.h"
 #include "ui/icon-loader.h"
 #include "ui/icon-names.h"
-#include "ui/widget/iconrenderer.h"
-
+#include "ui/syntax.h"
+#include "ui/util.h"
+#include "ui/widget/shapeicon.h"
+#include "util/numeric/converters.h"
+#include "util/trim.h"
 #include "xml/attribute-record.h"
 
+#include <cstddef>
 #include <gdk/gdkkeysyms.h>
 #include <glibmm/i18n.h>
+#include <glibmm/main.h>
+#include <glibmm/regex.h>
+#include <glibmm/timer.h>
+#include <glibmm/ustring.h>
+#include <gtkmm/box.h>
+#include <gtkmm/button.h>
+#include <gtkmm/enums.h>
+#include <gtkmm/label.h>
+#include <gtkmm/liststore.h>
+#include <gtkmm/menuitem.h>
+#include <gtkmm/object.h>
+#include <gtkmm/popover.h>
+#include <gtkmm/scrolledwindow.h>
+#include <gtkmm/targetlist.h>
+#include <gtkmm/textview.h>
+#include <gtkmm/treeview.h>
+#include <gtkmm/widget.h>
+#include <memory>
+#include <string>
+
+#include "config.h"
+#if WITH_GSOURCEVIEW
+#   include <gtksourceview/gtksource.h>
+#endif
 
 /**
  * Return true if `node` is a text or comment node
@@ -41,11 +74,43 @@ static bool is_text_or_comment_node(Inkscape::XML::Node const &node)
     }
 }
 
-namespace Inkscape {
-namespace UI {
-namespace Dialog {
+static Glib::ustring get_syntax_theme()
+{
+    return Inkscape::Preferences::get()->getString("/theme/syntax-color-theme", "-none-");
+}
+
+namespace Inkscape::UI::Dialog {
+
+// arbitrarily selected size limits
+constexpr int MAX_POPOVER_HEIGHT = 450;
+constexpr int MAX_POPOVER_WIDTH = 520;
+constexpr int TEXT_MARGIN = 3;
+
+std::unique_ptr<Syntax::TextEditView> AttrDialog::init_text_view(AttrDialog* owner, Syntax::SyntaxMode coloring, bool map)
+{
+    auto edit = Syntax::TextEditView::create(coloring);
+    auto& textview = edit->getTextView();
+    textview.set_wrap_mode(Gtk::WrapMode::WRAP_WORD);
+
+    // this actually sets padding rather than margin and extends textview's background color to the sides
+    textview.set_top_margin(TEXT_MARGIN);
+    textview.set_left_margin(TEXT_MARGIN);
+    textview.set_right_margin(TEXT_MARGIN);
+    textview.set_bottom_margin(TEXT_MARGIN);
+
+    if (map) {
+        textview.signal_map().connect([owner](){
+            // this is not effective: text view recalculates its size on idle, so it's too early to call on 'map';
+            // (note: there's no signal on a TextView to tell us that formatting has been done)
+            // delay adjustment; this will work if UI is fast enough, but at the cost of popup jumping,
+            // but at least it will be sized properly
+            owner->_adjust_size = Glib::signal_timeout().connect([=](){ owner->adjust_popup_edit_size(); return false; }, 50);
+        });
+    }
+
+    return edit;
+}
 
-static gboolean key_callback(GtkWidget *widget, GdkEventKey *event, AttrDialog *attrdialog);
 /**
  * Constructor
  * A treeview whose each row corresponds to an XML attribute of a selected node
@@ -53,46 +118,45 @@ static gboolean key_callback(GtkWidget *widget, GdkEventKey *event, AttrDialog *
  */
 AttrDialog::AttrDialog()
     : DialogBase("/dialogs/attr", "AttrDialog")
-    , _mainBox(Gtk::ORIENTATION_VERTICAL)
-    , status_box(Gtk::ORIENTATION_HORIZONTAL)
+    , _builder(create_builder("attribute-edit-component.glade"))
+    , _scrolled_text_view(get_widget<Gtk::ScrolledWindow>(_builder, "scroll-wnd"))
+    , _content_sw(get_widget<Gtk::ScrolledWindow>(_builder, "content-sw"))
+    , _scrolled_window(get_widget<Gtk::ScrolledWindow>(_builder, "scrolled-wnd"))
+    , _treeView(get_widget<Gtk::TreeView>(_builder, "tree-view"))
+    , _popover(&get_widget<Gtk::Popover>(_builder, "popup"))
+    , _status_box(get_widget<Gtk::Box>(_builder, "status-box"))
+    , _status(get_widget<Gtk::Label>(_builder, "status-label"))
 {
+    // Attribute value editing (with syntax highlighting).
+    using namespace Syntax;
+    _css_edit = init_text_view(this, SyntaxMode::InlineCss, true);
+    _svgd_edit = init_text_view(this, SyntaxMode::SvgPathData, true);
+    _points_edit = init_text_view(this, SyntaxMode::SvgPolyPoints, true);
+    _attr_edit = init_text_view(this, SyntaxMode::PlainText, true);
+
+    // string content editing
+    _text_edit = init_text_view(this, SyntaxMode::PlainText, false);
+    _style_edit = init_text_view(this, SyntaxMode::CssStyle, false);
+
     set_size_request(20, 15);
-    _mainBox.pack_start(_scrolledWindow, Gtk::PACK_EXPAND_WIDGET);
-
-    // For text and comment nodes
-    _content_tv = Gtk::manage(new Gtk::TextView());
-    _content_tv->show();
-    _content_tv->set_wrap_mode(Gtk::WrapMode::WRAP_CHAR);
-    _content_tv->set_monospace(true);
-    _content_tv->set_border_width(4);
-    _content_tv->set_buffer(Gtk::TextBuffer::create());
-    _content_tv->get_buffer()->signal_end_user_action().connect([this]() {
-        if (_repr) {
-            _repr->setContent(_content_tv->get_buffer()->get_text().c_str());
-            setUndo(_("Type text"));
-        }
-    });
-    _content_sw = Gtk::manage(new Gtk::ScrolledWindow());
-    _content_sw->hide();
-    _content_sw->set_no_show_all();
-    _content_sw->add(*_content_tv);
-    _mainBox.pack_start(*_content_sw);
-
-    // For element nodes
-    _treeView.set_headers_visible(true);
-    _treeView.set_hover_selection(true);
-    _treeView.set_activate_on_single_click(true);
-    _treeView.set_can_focus(false);
-    _scrolledWindow.add(_treeView);
-    _scrolledWindow.set_policy(Gtk::POLICY_AUTOMATIC, Gtk::POLICY_AUTOMATIC);
+
+    // For text and comment nodes: update XML on the fly, as users type
+    for (auto tv : {&_text_edit->getTextView(), &_style_edit->getTextView()}) {
+        tv->get_buffer()->signal_end_user_action().connect([=]() {
+            if (_repr) {
+                _repr->setContent(tv->get_buffer()->get_text().c_str());
+                setUndo(_("Type text"));
+            }
+        });
+    }
 
     _store = Gtk::ListStore::create(_attrColumns);
     _treeView.set_model(_store);
 
-    Inkscape::UI::Widget::IconRenderer * addRenderer = manage(new Inkscape::UI::Widget::IconRenderer());
-    addRenderer->add_icon("edit-delete");
-
-    _treeView.append_column("", *addRenderer);
+    // high-res aware icon renderer for a trash can
+    auto delete_renderer = manage(new Inkscape::UI::Widget::CellRendererItemIcon());
+    delete_renderer->property_shape_type().set_value("edit-delete");
+    _treeView.append_column("", *delete_renderer);
     Gtk::TreeViewColumn *col = _treeView.get_column(0);
     if (col) {
         auto add_icon = Gtk::manage(sp_get_icon_image("list-add", Gtk::ICON_SIZE_SMALL_TOOLBAR));
@@ -105,11 +169,10 @@ AttrDialog::AttrDialog()
         // isn't in this exact way, the onAttrDelete is called when the header lines are pressed.
         button->signal_button_release_event().connect(sigc::mem_fun(*this, &AttrDialog::onAttrCreate), false);
     }
-    addRenderer->signal_activated().connect(sigc::mem_fun(*this, &AttrDialog::onAttrDelete));
+    delete_renderer->signal_activated().connect(sigc::mem_fun(*this, &AttrDialog::onAttrDelete));
     _treeView.signal_key_press_event().connect(sigc::mem_fun(*this, &AttrDialog::onKeyPressed));
-    _treeView.set_search_column(-1);
 
-    _nameRenderer = Gtk::manage(new Gtk::CellRendererText());
+    _nameRenderer = Gtk::make_managed<Gtk::CellRendererText>();
     _nameRenderer->property_editable() = true;
     _nameRenderer->property_placeholder_text().set_value(_("Attribute Name"));
     _nameRenderer->signal_edited().connect(sigc::mem_fun(*this, &AttrDialog::nameEdited));
@@ -120,114 +183,174 @@ AttrDialog::AttrDialog()
         _nameCol->set_resizable(true);
         _nameCol->add_attribute(_nameRenderer->property_text(), _attrColumns._attributeName);
     }
-    status.set_halign(Gtk::ALIGN_START);
-    status.set_valign(Gtk::ALIGN_CENTER);
-    status.set_size_request(1, -1);
-    status.set_markup("");
-    status.set_line_wrap(true);
-    status.get_style_context()->add_class("inksmall");
-    status_box.pack_start(status, TRUE, TRUE, 0);
-    pack_end(status_box, false, false, 2);
 
     _message_stack = std::make_shared<Inkscape::MessageStack>();
-    _message_context = std::unique_ptr<Inkscape::MessageContext>(new Inkscape::MessageContext(_message_stack));
-    _message_changed_connection =
-        _message_stack->connectChanged(sigc::bind(sigc::ptr_fun(_set_status_message), GTK_WIDGET(status.gobj())));
+    _message_context = std::make_unique<Inkscape::MessageContext>(_message_stack);
+    _message_changed_connection = _message_stack->connectChanged([=](MessageType, const char* message) {
+        _status.set_markup(message ? message : "");
+    });
 
-    _valueRenderer = Gtk::manage(new Gtk::CellRendererText());
+    _valueRenderer = Gtk::make_managed<Gtk::CellRendererText>();
     _valueRenderer->property_editable() = true;
     _valueRenderer->property_placeholder_text().set_value(_("Attribute Value"));
     _valueRenderer->property_ellipsize().set_value(Pango::ELLIPSIZE_END);
     _valueRenderer->signal_edited().connect(sigc::mem_fun(*this, &AttrDialog::valueEdited));
-    _valueRenderer->signal_editing_started().connect(sigc::mem_fun(*this, &AttrDialog::startValueEdit));
+    _valueRenderer->signal_editing_started().connect(sigc::mem_fun(*this, &AttrDialog::startValueEdit), true);
     _treeView.append_column(_("Value"), *_valueRenderer);
     _valueCol = _treeView.get_column(2);
     if (_valueCol) {
         _valueCol->add_attribute(_valueRenderer->property_text(), _attrColumns._attributeValueRender);
     }
-    _popover = Gtk::manage(new Gtk::Popover());
-    Gtk::Box *vbox = Gtk::manage(new Gtk::Box(Gtk::ORIENTATION_VERTICAL));
-    Gtk::Box *hbox = Gtk::manage(new Gtk::Box(Gtk::ORIENTATION_HORIZONTAL));
-    _textview = Gtk::manage(new Gtk::TextView());
-    _textview->set_wrap_mode(Gtk::WrapMode::WRAP_CHAR);
-    _textview->set_editable(true);
-    _textview->set_monospace(true);
-    _textview->set_border_width(6);
-    _textview->signal_map().connect(sigc::mem_fun(*this, &AttrDialog::textViewMap));
-    Glib::RefPtr<Gtk::TextBuffer> textbuffer = Gtk::TextBuffer::create();
-    textbuffer->set_text("");
-    _textview->set_buffer(textbuffer);
-    _scrolled_text_view.add(*_textview);
-    _scrolled_text_view.set_max_content_height(450);
-    _scrolled_text_view.set_policy(Gtk::POLICY_AUTOMATIC, Gtk::POLICY_AUTOMATIC);
-    _scrolled_text_view.set_propagate_natural_width(true);
-    Gtk::Label *helpreturn = Gtk::manage(new Gtk::Label(_("Shift+Return for a new line")));
-    helpreturn->get_style_context()->add_class("inksmall");
-    Gtk::Button *apply = Gtk::manage(new Gtk::Button());
-    Gtk::Image *icon = Gtk::manage(sp_get_icon_image("on-outline", 26));
-    apply->set_relief(Gtk::RELIEF_NONE);
-    icon->show();
-    apply->add(*icon);
-    apply->signal_clicked().connect(sigc::mem_fun(*this, &AttrDialog::valueEditedPop));
-    Gtk::Button *cancel = Gtk::manage(new Gtk::Button());
-    icon = Gtk::manage(sp_get_icon_image("off-outline", 26));
-    cancel->set_relief(Gtk::RELIEF_NONE);
-    icon->show();
-    cancel->add(*icon);
-    cancel->signal_clicked().connect(sigc::mem_fun(*this, &AttrDialog::valueCanceledPop));
-    hbox->pack_end(*apply, Gtk::PACK_SHRINK, 3);
-    hbox->pack_end(*cancel, Gtk::PACK_SHRINK, 3);
-    hbox->pack_end(*helpreturn, Gtk::PACK_SHRINK, 3);
-    vbox->pack_start(_scrolled_text_view, Gtk::PACK_EXPAND_WIDGET, 3);
-    vbox->pack_start(*hbox, Gtk::PACK_EXPAND_WIDGET, 3);
-    _popover->add(*vbox);
-    _popover->show();
-    _popover->set_relative_to(_treeView);
-    _popover->set_position(Gtk::PositionType::POS_BOTTOM);
-    _popover->signal_closed().connect(sigc::mem_fun(*this, &AttrDialog::popClosed));
-    _popover->get_style_context()->add_class("attrpop");
-    attr_reset_context(0);
-    pack_start(_mainBox, Gtk::PACK_EXPAND_WIDGET);
-    // I couldn't get the signal go well not using C way signals
-    g_signal_connect(GTK_WIDGET(_popover->gobj()), "key-press-event", G_CALLBACK(key_callback), this);
+
+    set_current_textedit(_attr_edit.get());
+    _scrolled_text_view.set_max_content_height(MAX_POPOVER_HEIGHT);
+
+    auto& apply = get_widget<Gtk::Button>(_builder, "btn-ok");
+    apply.signal_clicked().connect([=]() { valueEditedPop(); });
+
+    auto& cancel = get_widget<Gtk::Button>(_builder, "btn-cancel");
+    cancel.signal_clicked().connect([=](){
+        if (!_value_editing.empty()) {
+            _activeTextView().get_buffer()->set_text(_value_editing);
+        }
+        _popover->popdown();
+    });
+
+    _popover->signal_closed().connect([=]() { popClosed(); });
+    _popover->signal_key_press_event().connect([=](GdkEventKey* ev) { return key_callback(ev); }, false);
     _popover->hide();
+
+    get_widget<Gtk::Button>(_builder, "btn-truncate").signal_clicked().connect([=](){ truncateDigits(); });
+
+    const int N = 5;
+    _rounding_precision = Inkscape::Preferences::get()->getIntLimited("/dialogs/attrib/precision", 2, 0, N);
+    for (int n = 0; n <= N; ++n) {
+        auto id = '_' + std::to_string(n);
+        auto item = &get_widget<Gtk::MenuItem>(_builder, id.c_str());
+        auto action = [=](){
+            _rounding_precision = n;
+            get_widget<Gtk::Label>(_builder, "precision").set_label(' ' + item->get_label());
+            Inkscape::Preferences::get()->setInt("/dialogs/attrib/precision", n);
+        };
+        item->signal_activate().connect(action);
+
+        if (n == _rounding_precision) {
+            action();
+        }
+    }
+
+    attr_reset_context(0);
+    pack_start(get_widget<Gtk::Box>(_builder, "main-box"), Gtk::PACK_EXPAND_WIDGET);
     _updating = false;
 }
 
-void AttrDialog::textViewMap()
+AttrDialog::~AttrDialog()
 {
-    auto vscroll = _scrolled_text_view.get_vadjustment();
-    int height = vscroll->get_upper() + 12; // padding 6+6
-    if (height < 450) {
-        _scrolled_text_view.set_min_content_height(height);
-        vscroll->set_value(vscroll->get_lower());
+    _current_text_edit = nullptr;
+    _popover->hide();
+}
+
+
+static int fmt_number(_GMatchInfo const *match, _GString *ret, void *prec)
+{
+    auto number = g_match_info_fetch(match, 1);
+
+    char *end;
+    double val = g_ascii_strtod(number, &end);
+    if (*number && (end == nullptr || end > number)) {
+        auto precision = *static_cast<int*>(prec);
+        auto fmt = Util::format_number(val, precision);
+        g_string_append(ret, fmt.c_str());
     } else {
-        _scrolled_text_view.set_min_content_height(450);
+        g_string_append(ret, number);
+    }
+
+    auto text = g_match_info_fetch(match, 2);
+    g_string_append(ret, text);
+
+    g_free(number);
+    g_free(text);
+
+    return false;
+}
+
+Glib::ustring AttrDialog::round_numbers(const Glib::ustring& text, int precision)
+{
+    // match floating point number followed by something else (not a number); repeat
+    static const auto numbers = Glib::Regex::create("([-+]?(?:(?:\\d+\\.?\\d*)|(?:\\.\\d+))(?:[eE][-+]?\\d*)?)([^+\\-0-9]*)", Glib::REGEX_MULTILINE);
+
+    return numbers->replace_eval(text, text.size(), 0, Glib::RegexMatchFlags::REGEX_MATCH_NOTEMPTY, &fmt_number, &precision);
+}
+
+/** Round the selected floating point numbers in the attribute edit popover. */
+void AttrDialog::truncateDigits() const
+{
+    if (!_current_text_edit) {
+        return;
+    }
+
+    auto buffer = _current_text_edit->getTextView().get_buffer();
+    auto start = buffer->begin();
+    auto end = buffer->end();
+
+    bool const had_selection = buffer->get_has_selection();
+    int start_idx = 0, end_idx = 0;
+    if (had_selection) {
+        buffer->get_selection_bounds(start, end);
+        start_idx = start.get_offset();
+        end_idx = end.get_offset();
+    }
+
+    auto text = buffer->get_text(start, end);
+    auto ret = round_numbers(text, _rounding_precision);
+    buffer->erase(start, end);
+    buffer->insert_at_cursor(ret);
+
+    if (had_selection) {
+        // Restore selection but note that its length may have decreased.
+        end_idx -= text.size() - ret.size();
+        if (end_idx < start_idx) {
+            end_idx = start_idx;
+        }
+        buffer->select_range(buffer->get_iter_at_offset(start_idx), buffer->get_iter_at_offset(end_idx));
     }
 }
 
-gboolean sp_show_pop_map(gpointer data)
+void AttrDialog::set_current_textedit(Syntax::TextEditView* edit)
 {
-    AttrDialog *attrdialog = reinterpret_cast<AttrDialog *>(data);
-    attrdialog->textViewMap();
-    return FALSE;
+    _current_text_edit = edit ? edit : _attr_edit.get();
+    _scrolled_text_view.remove();
+    _scrolled_text_view.add(_current_text_edit->getTextView());
+    _scrolled_text_view.show_all();
 }
 
-static gboolean key_callback(GtkWidget *widget, GdkEventKey *event, AttrDialog *attrdialog)
+void AttrDialog::adjust_popup_edit_size()
 {
+    auto vscroll = _scrolled_text_view.get_vadjustment();
+    int height = vscroll->get_upper() + 2 * TEXT_MARGIN;
+    if (height < MAX_POPOVER_HEIGHT) {
+        _scrolled_text_view.set_min_content_height(height);
+        vscroll->set_value(vscroll->get_lower());
+    } else {
+        _scrolled_text_view.set_min_content_height(MAX_POPOVER_HEIGHT);
+    }
+}
+
+bool AttrDialog::key_callback(GdkEventKey* event) {
     switch (event->keyval) {
         case GDK_KEY_Return:
-        case GDK_KEY_KP_Enter: {
-            if (attrdialog->_popover->is_visible()) {
-                if (!(event->state & GDK_SHIFT_MASK)) {
-                    attrdialog->valueEditedPop();
-                    attrdialog->_popover->hide();
+        case GDK_KEY_KP_Enter:
+            if (_popover->is_visible()) {
+                if (event->state & GDK_SHIFT_MASK) {
+                    valueEditedPop();
                     return true;
-                } else {
-                    g_timeout_add(50, &sp_show_pop_map, attrdialog);
+                }
+                else {
+                    // as we type and content grows, resize the popup to accommodate it
+                    _adjust_size = Glib::signal_timeout().connect([=](){ adjust_popup_edit_size(); return false; }, 50);
                 }
             }
-        } break;
+        break;
     }
     return false;
 }
@@ -245,7 +368,6 @@ static Glib::ustring prepare_rendervalue(const char *value)
 {
     constexpr int MAX_LENGTH = 500; // maximum length of string before it's truncated for performance reasons
                                     // ~400 characters fit horizontally on a WQHD display, so 500 should be plenty
-
     Glib::ustring renderval;
 
     // truncate to MAX_LENGTH
@@ -264,16 +386,25 @@ static Glib::ustring prepare_rendervalue(const char *value)
     return renderval;
 }
 
+void set_mono_class(Gtk::Widget* widget, bool mono)
+{
+    if (!widget) {
+        return;
+    }
+    Glib::ustring class_name = "mono-font";
+    auto style = widget->get_style_context();
+    auto has_class = style->has_class(class_name);
+
+    if (mono && !has_class) {
+        style->add_class(class_name);
+    } else if (!mono && has_class) {
+        style->remove_class(class_name);
+    }
+}
 
-/**
- * @brief AttrDialog::~AttrDialog
- * Class destructor
- */
-AttrDialog::~AttrDialog()
+void AttrDialog::set_mono_font(bool mono)
 {
-    _message_changed_connection.disconnect();
-    _message_context = nullptr;
-    _message_stack = nullptr;
+    set_mono_class(&_treeView, mono);
 }
 
 void AttrDialog::startNameEdit(Gtk::CellEditable *cell, const Glib::ustring &path)
@@ -282,67 +413,100 @@ void AttrDialog::startNameEdit(Gtk::CellEditable *cell, const Glib::ustring &pat
     entry->signal_key_press_event().connect(sigc::bind(sigc::mem_fun(*this, &AttrDialog::onNameKeyPressed), entry));
 }
 
-
-gboolean sp_show_attr_pop(gpointer data)
+Gtk::TextView &AttrDialog::_activeTextView() const
 {
-    AttrDialog *attrdialog = reinterpret_cast<AttrDialog *>(data);
-    attrdialog->_popover->show_all();
-
-    return FALSE;
+    return _current_text_edit->getTextView();
 }
 
-gboolean sp_close_entry(gpointer data)
+void AttrDialog::startValueEdit(Gtk::CellEditable *cell, const Glib::ustring &path)
 {
-    Gtk::CellEditable *cell = reinterpret_cast<Gtk::CellEditable *>(data);
-    if (cell) {
-        cell->property_editing_canceled() = true;
-        cell->remove_widget();
+    _value_path = path;
+    Gtk::TreeIter iter = *_store->get_iter(path);
+    Gtk::TreeModel::Row row = *iter;
+    if (!row || !_repr || !cell) {
+        return;
     }
-    return FALSE;
-}
 
-void AttrDialog::startValueEdit(Gtk::CellEditable *cell, const Glib::ustring &path)
-{
-    Gtk::Entry *entry = dynamic_cast<Gtk::Entry *>(cell);
-    int width = 0;
-    int height = 0;
-    int colwidth = _valueCol->get_width();
     // popover in GTK3 is clipped to dialog window (in a floating dialog); limit size:
-    int dlg_width = get_allocated_width() - 10;
-    _textview->set_size_request(std::min(510, dlg_width), -1);
-    _popover->set_size_request(std::min(520, dlg_width), -1);
-    valuepath = path;
+    const int dlg_width = get_allocated_width() - 10;
+    _popover->set_size_request(std::min(MAX_POPOVER_WIDTH, dlg_width), -1);
+
+    auto const attribute = row[_attrColumns._attributeName];
+    bool edit_in_popup =
+#if WITH_GSOURCEVIEW
+    true;
+#else
+    false;
+#endif
+    bool enable_rouding = false;
+
+    if (attribute == "style") {
+        set_current_textedit(_css_edit.get());
+    } else if (attribute == "d") {
+        enable_rouding = true;
+        set_current_textedit(_svgd_edit.get());
+    } else if (attribute == "points") {
+        enable_rouding = true;
+        set_current_textedit(_points_edit.get());
+    } else {
+        set_current_textedit(_attr_edit.get());
+        edit_in_popup = false;
+    }
+
+    // number rounding functionality
+    widget_show(get_widget<Gtk::Box>(_builder, "rounding-box"), enable_rouding);
+
+    _activeTextView().set_size_request(std::min(MAX_POPOVER_WIDTH - 10, dlg_width), -1);
+
+    auto theme = get_syntax_theme();
+
+    auto entry = dynamic_cast<Gtk::Entry*>(cell);
+    int width, height;
     entry->get_layout()->get_pixel_size(width, height);
-    Gtk::TreeIter iter = *_store->get_iter(path);
-    Gtk::TreeModel::Row row = *iter;
-    if (row && this->_repr) {
-        Glib::ustring name = row[_attrColumns._attributeName];
-        if (row[_attrColumns._attributeValue] != row[_attrColumns._attributeValueRender] || colwidth - 10 < width) {
-            valueediting = entry->get_text();
-            Gdk::Rectangle rect;
-            _treeView.get_cell_area((Gtk::TreeModel::Path)iter, *_valueCol, rect);
-            if (_popover->get_position() == Gtk::PositionType::POS_BOTTOM) {
-                rect.set_y(rect.get_y() + 20);
-            }
-            _popover->set_pointing_to(rect);
-            Glib::RefPtr<Gtk::TextBuffer> textbuffer = Gtk::TextBuffer::create();
-            textbuffer->set_text(row[_attrColumns._attributeValue]);
-            _textview->set_buffer(textbuffer);
-            g_timeout_add(50, &sp_close_entry, cell);
-            g_timeout_add(50, &sp_show_attr_pop, this);
-        } else {
-            entry->signal_key_press_event().connect(
-                sigc::bind(sigc::mem_fun(*this, &AttrDialog::onValueKeyPressed), entry));
+    int colwidth = _valueCol->get_width();
+
+    if (row[_attrColumns._attributeValue] != row[_attrColumns._attributeValueRender] ||
+        edit_in_popup || colwidth - 10 < width)
+    {
+        _value_editing = entry->get_text();
+        Gdk::Rectangle rect;
+        _treeView.get_cell_area((Gtk::TreeModel::Path)iter, *_valueCol, rect);
+        if (_popover->get_position() == Gtk::PositionType::POS_BOTTOM) {
+            rect.set_y(rect.get_y() + 20);
+        }
+        if (rect.get_x() >= dlg_width) {
+            rect.set_x(dlg_width - 1);
         }
+        _popover->set_pointing_to(rect);
+
+        auto current_value = row[_attrColumns._attributeValue];
+        _current_text_edit->setStyle(theme);
+        _current_text_edit->setText(current_value);
+
+        // close in-line entry
+        cell->property_editing_canceled() = true;
+        cell->remove_widget();
+        // cannot dismiss it right away without warning from GTK, so delay it
+        Glib::signal_timeout().connect_once([=](){
+            cell->editing_done(); // only this call will actually remove in-line edit widget
+            cell->remove_widget();
+        }, 0);
+        // and show popup edit instead
+        Glib::signal_timeout().connect_once([=](){ _popover->popup(); }, 10);
+    } else {
+        entry->signal_key_press_event().connect(
+            sigc::bind(sigc::mem_fun(*this, &AttrDialog::onValueKeyPressed), entry));
     }
 }
 
 void AttrDialog::popClosed()
 {
-    Glib::RefPtr<Gtk::TextBuffer> textbuffer = Gtk::TextBuffer::create();
-    textbuffer->set_text("");
-    _textview->set_buffer(textbuffer);
-    _scrolled_text_view.set_min_content_height(20);
+    if (!_current_text_edit) {
+        return;
+    }
+    _activeTextView().get_buffer()->set_text("");
+    // delay this resizing, so it is not visible as popover fades out
+    _close_popup = Glib::signal_timeout().connect([=](){ _scrolled_text_view.set_min_content_height(20); return false; }, 250);
 }
 
 /**
@@ -351,7 +515,9 @@ void AttrDialog::popClosed()
  */
 void AttrDialog::setRepr(Inkscape::XML::Node * repr)
 {
-    if ( repr == _repr ) return;
+    if (repr == _repr) {
+        return;
+    }
     if (_repr) {
         _store->clear();
         _repr->removeObserver(*this);
@@ -362,12 +528,25 @@ void AttrDialog::setRepr(Inkscape::XML::Node * repr)
     if (repr) {
         Inkscape::GC::anchor(_repr);
         _repr->addObserver(*this);
-        _repr->synthesizeEvents(*this);
 
         // show either attributes or content
         bool show_content = is_text_or_comment_node(*_repr);
-        _scrolledWindow.set_visible(!show_content);
-        _content_sw->set_visible(show_content);
+        if (show_content) {
+            _content_sw.remove();
+            auto type = repr->name();
+            auto elem = repr->parent();
+            if (type && strcmp(type, "string") == 0 && elem && elem->name() && strcmp(elem->name(), "svg:style") == 0) {
+                // editing embedded CSS style
+                _style_edit->setStyle(get_syntax_theme());
+                _content_sw.add(_style_edit->getTextView());
+            } else {
+                _content_sw.add(_text_edit->getTextView());
+            }
+        }
+
+        _repr->synthesizeEvents(*this);
+        _scrolled_window.set_visible(!show_content);
+        _content_sw.set_visible(show_content);
     }
 }
 
@@ -376,13 +555,6 @@ void AttrDialog::setUndo(Glib::ustring const &event_description)
     DocumentUndo::done(getDocument(), event_description, INKSCAPE_ICON("dialog-xml-editor"));
 }
 
-void AttrDialog::_set_status_message(Inkscape::MessageType /*type*/, const gchar *message, GtkWidget *widget)
-{
-    if (widget) {
-        gtk_label_set_markup(GTK_LABEL(widget), message ? message : "");
-    }
-}
-
 /**
  * Sets the AttrDialog status bar, depending on which attr is selected.
  */
@@ -414,12 +586,11 @@ void AttrDialog::notifyAttributeChanged(XML::Node&, GQuark name_, Util::ptr_shar
     if (new_value) {
         renderval = prepare_rendervalue(new_value.pointer());
     }
-    for(auto iter: this->_store->children())
-    {
+    for (auto&& iter : _store->children()) {
         Gtk::TreeModel::Row row = *iter;
         Glib::ustring col_name = row[_attrColumns._attributeName];
-        if(name == col_name) {
-            if(new_value) {
+        if (name == col_name) {
+            if (new_value) {
                 row[_attrColumns._attributeValue] = new_value.pointer();
                 row[_attrColumns._attributeValueRender] = renderval;
                 new_value = Util::ptr_shared(); // Don't make a new one
@@ -430,7 +601,7 @@ void AttrDialog::notifyAttributeChanged(XML::Node&, GQuark name_, Util::ptr_shar
         }
     }
     if (new_value) {
-        Gtk::TreeModel::Row row = *(_store->prepend());
+        Gtk::TreeModel::Row row = *_store->prepend();
         row[_attrColumns._attributeName] = name;
         row[_attrColumns._attributeValue] = new_value.pointer();
         row[_attrColumns._attributeValueRender] = renderval;
@@ -476,10 +647,14 @@ void AttrDialog::notifyContentChanged(XML::Node &,
 									  Util::ptr_shared,
 									  Util::ptr_shared new_content)
 {
-    auto buffer = _content_tv->get_buffer();
+    auto textview = dynamic_cast<Gtk::TextView *>(_content_sw.get_child());
+    if (!textview) {
+        return;
+    }
+    auto buffer = textview->get_buffer();
     if (!buffer->get_modified()) {
-        auto const c = new_content.pointer();
-        buffer->set_text(c ? c : "");
+        auto str = new_content.pointer();
+        buffer->set_text(str ? str : "");
     }
     buffer->set_modified(false);
 }
@@ -494,45 +669,41 @@ void AttrDialog::notifyContentChanged(XML::Node &,
 bool AttrDialog::onKeyPressed(GdkEventKey *event)
 {
     bool ret = false;
-    if(this->_repr) {
-        auto selection = this->_treeView.get_selection();
-        Gtk::TreeModel::Row row = *(selection->get_selected());
-        Gtk::TreeIter iter = *(selection->get_selected());
-        switch (event->keyval)
-        {
-            case GDK_KEY_Delete:
-            case GDK_KEY_KP_Delete: {
-                // Create new attribute (repeat code, fold into above event!)
-                Glib::ustring name = row[_attrColumns._attributeName];
-                {
-                    this->_store->erase(row);
-                    this->_repr->removeAttribute(name);
-                    this->setUndo(_("Delete attribute"));
-                }
-                ret = true;
+    if (!_repr) {
+        return ret;
+    }
+    auto selection = _treeView.get_selection();
+    auto row = *selection->get_selected();
+
+    switch (event->keyval) {
+        case GDK_KEY_Delete:
+        case GDK_KEY_KP_Delete: {
+            // Create new attribute (repeat code, fold into above event!)
+            Glib::ustring name = row[_attrColumns._attributeName];
+            _store->erase(row);
+            _repr->removeAttribute(name);
+            setUndo(_("Delete attribute"));
+            ret = true;
             } break;
-            case GDK_KEY_plus:
-            case GDK_KEY_Insert:
-              {
-                // Create new attribute (repeat code, fold into above event!)
-                Gtk::TreeIter iter = this->_store->prepend();
-                Gtk::TreeModel::Path path = (Gtk::TreeModel::Path)iter;
-                this->_treeView.set_cursor(path, *this->_nameCol, true);
-                grab_focus();
-                ret = true;
+
+        case GDK_KEY_plus:
+        case GDK_KEY_Insert: {
+            // Create new attribute (repeat code, fold into above event!)
+            Gtk::TreeIter iter = _store->prepend();
+            Gtk::TreeModel::Path path = (Gtk::TreeModel::Path)iter;
+            _treeView.set_cursor(path, *_nameCol, true);
+            grab_focus();
+            ret = true;
             } break;
-            case GDK_KEY_Return:
-            case GDK_KEY_KP_Enter: {
-                if (_popover->is_visible()) {
-                    if (!(event->state & GDK_SHIFT_MASK)) {
-                        valueEditedPop();
-                        _popover->hide();
-                        ret = true;
-                    }
-                }
+
+        case GDK_KEY_Return:
+        case GDK_KEY_KP_Enter:
+            if (_popover->is_visible() && (event->state & GDK_SHIFT_MASK)) {
+                valueEditedPop();
+                ret = true;
             } break;
-        }
     }
+
     return ret;
 }
 
@@ -550,7 +721,6 @@ bool AttrDialog::onNameKeyPressed(GdkEventKey *event, Gtk::Entry *entry)
     return ret;
 }
 
-
 bool AttrDialog::onValueKeyPressed(GdkEventKey *event, Gtk::Entry *entry)
 {
     g_debug("StyleDialog::_onValueKeyPressed");
@@ -565,37 +735,30 @@ bool AttrDialog::onValueKeyPressed(GdkEventKey *event, Gtk::Entry *entry)
     return ret;
 }
 
-gboolean sp_attrdialog_store_move_to_next(gpointer data)
+void AttrDialog::storeMoveToNext(Gtk::TreeModel::Path modelpath)
 {
-    AttrDialog *attrdialog = reinterpret_cast<AttrDialog *>(data);
-    auto selection = attrdialog->_treeView.get_selection();
-    Gtk::TreeIter iter = *(selection->get_selected());
-    Gtk::TreeModel::Path path = (Gtk::TreeModel::Path)iter;
+    auto selection = _treeView.get_selection();
+    auto iter = *(selection->get_selected());
+    auto path = static_cast<Gtk::TreeModel::Path>(iter);
     Gtk::TreeViewColumn *focus_column;
-    attrdialog->_treeView.get_cursor(path, focus_column);
-    if (path == attrdialog->_modelpath && focus_column == attrdialog->_treeView.get_column(1)) {
-        attrdialog->_treeView.set_cursor(attrdialog->_modelpath, *attrdialog->_valueCol, true);
+    _treeView.get_cursor(path, focus_column);
+    if (path == modelpath && focus_column == _treeView.get_column(1)) {
+        _treeView.set_cursor(modelpath, *_valueCol, true);
     }
-    return FALSE;
 }
 
 /**
- *
- *
- * @brief AttrDialog::nameEdited
- * @param event
- * @return
  * Called when the name is edited in the TreeView editable column
  */
 void AttrDialog::nameEdited (const Glib::ustring& path, const Glib::ustring& name)
 {
     Gtk::TreeIter iter = *_store->get_iter(path);
-    _modelpath = (Gtk::TreeModel::Path)iter;
+    auto modelpath = static_cast<Gtk::TreeModel::Path>(iter);
     Gtk::TreeModel::Row row = *iter;
     if(row && this->_repr) {
         Glib::ustring old_name = row[_attrColumns._attributeName];
         if (old_name == name) {
-            g_timeout_add(50, &sp_attrdialog_store_move_to_next, this);
+            Glib::signal_timeout().connect_once([=](){ storeMoveToNext(modelpath); }, 50);
             grab_focus();
             return;
         }
@@ -628,27 +791,16 @@ void AttrDialog::nameEdited (const Glib::ustring& path, const Glib::ustring& nam
         _updating = true;
         _repr->setAttributeOrRemoveIfEmpty(name, value); // use char * overload (allows empty attribute values)
         _updating = false;
-        g_timeout_add(50, &sp_attrdialog_store_move_to_next, this);
-        this->setUndo(_("Rename attribute"));
+        Glib::signal_timeout().connect_once([=](){ storeMoveToNext(modelpath); }, 50);
+        setUndo(_("Rename attribute"));
     }
 }
 
 void AttrDialog::valueEditedPop()
 {
-    Glib::ustring value = _textview->get_buffer()->get_text();
-    valueEdited(valuepath, value);
-    valueediting = "";
-    _popover->hide();
-}
-
-void AttrDialog::valueCanceledPop()
-{
-    if (!valueediting.empty()) {
-        Glib::RefPtr<Gtk::TextBuffer> textbuffer = Gtk::TextBuffer::create();
-        textbuffer->set_text(valueediting);
-        _textview->set_buffer(textbuffer);
-    }
-    _popover->hide();
+    valueEdited(_value_path, _current_text_edit->getText());
+    _value_editing.clear();
+    _popover->popdown();
 }
 
 /**
@@ -664,17 +816,16 @@ void AttrDialog::valueEdited (const Glib::ustring& path, const Glib::ustring& va
     }
 
     Gtk::TreeModel::Row row = *_store->get_iter(path);
-    if(row && this->_repr) {
+    if (row && _repr) {
         Glib::ustring name = row[_attrColumns._attributeName];
         Glib::ustring old_value = row[_attrColumns._attributeValue];
-        if (old_value == value) {
+        if (old_value == value || name.empty()) {
             return;
         }
-        if(name.empty()) return;
-        {
-            _repr->setAttributeOrRemoveIfEmpty(name, value);
-        }
-        if(!value.empty()) {
+
+        _repr->setAttributeOrRemoveIfEmpty(name, value);
+
+        if (!value.empty()) {
             row[_attrColumns._attributeValue] = value;
             Glib::ustring renderval = prepare_rendervalue(value.c_str());
             row[_attrColumns._attributeValueRender] = renderval;
@@ -683,6 +834,4 @@ void AttrDialog::valueEdited (const Glib::ustring& path, const Glib::ustring& va
     }
 }
 
-} // namespace Dialog
-} // namespace UI
-} // namespace Inkscape
+} // namespace Inkscape::UI::Dialog
diff --git a/src/ui/dialog/attrdialog.h b/src/ui/dialog/attrdialog.h
index 6d33a6668c..e85d42d722 100644
--- a/src/ui/dialog/attrdialog.h
+++ b/src/ui/dialog/attrdialog.h
@@ -13,16 +13,20 @@
 #ifndef SEEN_UI_DIALOGS_ATTRDIALOG_H
 #define SEEN_UI_DIALOGS_ATTRDIALOG_H
 
+#include <gtkmm/builder.h>
 #include <gtkmm/dialog.h>
 #include <gtkmm/liststore.h>
 #include <gtkmm/popover.h>
 #include <gtkmm/scrolledwindow.h>
 #include <gtkmm/textview.h>
 #include <gtkmm/treeview.h>
+#include <memory>
 
+#include "helper/auto-connection.h"
+#include "inkscape-application.h"
 #include "message.h"
 #include "ui/dialog/dialog-base.h"
-
+#include "ui/syntax.h"
 #include "xml/node-observer.h"
 
 namespace Inkscape {
@@ -44,6 +48,16 @@ public:
     AttrDialog();
     ~AttrDialog() override;
 
+    void setRepr(Inkscape::XML::Node * repr);
+    Gtk::ScrolledWindow& get_scrolled_window() { return _scrolled_window; }
+    Gtk::Box& get_status_box() { return _status_box; }
+    void adjust_popup_edit_size();
+    void set_mono_font(bool mono);
+
+private:
+    // builder comes first, so it is initialized before other data members
+    Glib::RefPtr<Gtk::Builder> _builder;
+
     // Data structure
     class AttrColumns : public Gtk::TreeModel::ColumnRecord
     {
@@ -61,69 +75,75 @@ public:
     AttrColumns _attrColumns;
 
     // TreeView
-    Gtk::TreeView _treeView;
+    Gtk::TreeView& _treeView;
     Glib::RefPtr<Gtk::ListStore> _store;
     Gtk::CellRendererText *_nameRenderer;
     Gtk::CellRendererText *_valueRenderer;
     Gtk::TreeViewColumn *_nameCol;
     Gtk::TreeViewColumn *_valueCol;
-    Gtk::TreeModel::Path _modelpath;
     Gtk::Popover *_popover;
-    Gtk::TextView *_textview;
-    Glib::ustring valuepath;
-    Glib::ustring valueediting;
-
-    // Text/comment nodes
-    Gtk::TextView *_content_tv;
-    Gtk::ScrolledWindow *_content_sw;
-
-    /**
-     * Status bar
-     */
+    Glib::ustring _value_path;
+    Glib::ustring _value_editing;
+    // Status bar
     std::shared_ptr<Inkscape::MessageStack> _message_stack;
     std::unique_ptr<Inkscape::MessageContext> _message_context;
-
     // Widgets
-    Gtk::Box _mainBox;
-    Gtk::ScrolledWindow _scrolledWindow;
-    Gtk::ScrolledWindow _scrolled_text_view;
-    Gtk::Button _buttonAddAttribute;
+    Gtk::ScrolledWindow& _scrolled_window;
+    Gtk::ScrolledWindow& _scrolled_text_view;
     // Variables - Inkscape
     Inkscape::XML::Node* _repr{nullptr};
-    Gtk::Box status_box;
-    Gtk::Label status;
-    bool _updating;
+    Gtk::Box& _status_box;
+    Gtk::Label& _status;
+    bool _updating = true;
 
     // Helper functions
-    void setRepr(Inkscape::XML::Node * repr);
     void setUndo(Glib::ustring const &event_description);
     /**
      * Sets the XML status bar, depending on which attr is selected.
      */
     void attr_reset_context(gint attr);
-    static void _set_status_message(Inkscape::MessageType type, const gchar *message, GtkWidget *dialog);
 
     /**
      * Signal handlers
      */
-    sigc::connection _message_changed_connection;
+    auto_connection _message_changed_connection;
     bool onNameKeyPressed(GdkEventKey *event, Gtk::Entry *entry);
     bool onValueKeyPressed(GdkEventKey *event, Gtk::Entry *entry);
     void onAttrDelete(Glib::ustring path);
     bool onAttrCreate(GdkEventButton *event);
     bool onKeyPressed(GdkEventKey *event);
+    void truncateDigits() const;
     void popClosed();
     void startNameEdit(Gtk::CellEditable *cell, const Glib::ustring &path);
     void startValueEdit(Gtk::CellEditable *cell, const Glib::ustring &path);
     void nameEdited(const Glib::ustring &path, const Glib::ustring &name);
     void valueEdited(const Glib::ustring &path, const Glib::ustring &value);
-    void textViewMap();
-    void valueCanceledPop();
     void valueEditedPop();
+    void storeMoveToNext(Gtk::TreeModel::Path modelpath);
 
 private:
+    // Text/comment nodes
+    Gtk::ScrolledWindow& _content_sw;
+    std::unique_ptr<Syntax::TextEditView> _text_edit;  // text content editing (plain text)
+    std::unique_ptr<Syntax::TextEditView> _style_edit; // embedded CSS style (with syntax coloring)
+
+    // Attribute value editing
+    std::unique_ptr<Syntax::TextEditView> _css_edit;    // in-line CSS style
+    std::unique_ptr<Syntax::TextEditView> _svgd_edit;   // SVG path data
+    std::unique_ptr<Syntax::TextEditView> _points_edit; // points in a <polygon> or <polyline>
+    std::unique_ptr<Syntax::TextEditView> _attr_edit;   // all other attributes (plain text)
+    Syntax::TextEditView* _current_text_edit = nullptr; // current text edit for attribute value editing
+    auto_connection _adjust_size;
+    auto_connection _close_popup;
+    int _rounding_precision = 0;
+
+    bool key_callback(GdkEventKey* event);
     void notifyAttributeChanged(XML::Node &repr, GQuark name, Util::ptr_shared old_value, Util::ptr_shared new_value) final;
 	void notifyContentChanged(XML::Node &node, Util::ptr_shared old_content, Util::ptr_shared new_content) final;
+    static Glib::ustring round_numbers(const Glib::ustring& text, int precision);
+    Gtk::TextView &_activeTextView() const;
+    void set_current_textedit(Syntax::TextEditView* edit);
+    static std::unique_ptr<Syntax::TextEditView> init_text_view(AttrDialog* owner, Syntax::SyntaxMode coloring, bool map);
 };
 
 } // namespace Dialog
diff --git a/src/ui/dialog/inkscape-preferences.cpp b/src/ui/dialog/inkscape-preferences.cpp
index 36d38961c9..29f99f4bfe 100644
--- a/src/ui/dialog/inkscape-preferences.cpp
+++ b/src/ui/dialog/inkscape-preferences.cpp
@@ -14,6 +14,11 @@
  * Released under GNU GPL v2+, read the file 'COPYING' for more information.
  */
 
+#include <glibmm/ustring.h>
+#include <gtkmm/dialog.h>
+#include <gtkmm/entry.h>
+#include <gtkmm/fontbutton.h>
+#include <gtkmm/fontchooserdialog.h>
 #include <gtkmm/widget.h>
 #ifdef HAVE_CONFIG_H
 # include "config.h"  // only include where actually required!
@@ -90,6 +95,10 @@
 # endif
 #endif
 
+#if WITH_GSOURCEVIEW
+#   include <gtksourceview/gtksource.h>
+#endif
+
 namespace Inkscape {
 namespace UI {
 namespace Dialog {
@@ -1692,7 +1701,7 @@ void InkscapePreferences::initPageUI()
     {
         auto font_scale = new Inkscape::UI::Widget::PrefSlider();
         font_scale = Gtk::manage(font_scale);
-        font_scale->init("/theme/fontscale", 50, 150, 5, 5, 100, 0); // 50% to 150%
+        font_scale->init(ThemeContext::get_font_scale_pref_path(), 50, 150, 5, 5, 100, 0); // 50% to 150%
         font_scale->getSlider()->signal_format_value().connect([=](double val) {
             return Glib::ustring::format(std::fixed, std::setprecision(0), val) + "%";
         });
@@ -1715,10 +1724,10 @@ void InkscapePreferences::initPageUI()
         space->add(*reset);
         reset->signal_clicked().connect([=](){
             font_scale->getSlider()->set_value(100);
-            INKSCAPE.themecontext->adjust_global_font_scale(1.0);
+            INKSCAPE.themecontext->adjustGlobalFontScale(1.0);
         });
         apply->signal_clicked().connect([=](){
-            INKSCAPE.themecontext->adjust_global_font_scale(font_scale->getSlider()->get_value() / 100.0);
+            INKSCAPE.themecontext->adjustGlobalFontScale(font_scale->getSlider()->get_value() / 100.0);
         });
         _page_theme.add_line(false, _("_Font scale:"), *font_scale, "", _("Adjust size of UI fonts"), true, space);
     }
@@ -1834,6 +1843,61 @@ void InkscapePreferences::initPageUI()
         _page_theme.add_line(true, "", _shift_icons, "",
                              _("This preference fixes icon positions in menus."), false, reset_icon());
 
+    _page_theme.add_group_header(_("XML dialog"));
+#if WITH_GSOURCEVIEW
+    {
+        auto manager = gtk_source_style_scheme_manager_get_default();
+        auto ids = gtk_source_style_scheme_manager_get_scheme_ids(manager);
+
+        auto syntax = Gtk::make_managed<UI::Widget::PrefCombo>();
+        std::vector<Glib::ustring> labels;
+        std::vector<Glib::ustring> values;
+        for (const char* style = *ids; style; style = *++ids) {
+            if (auto scheme = gtk_source_style_scheme_manager_get_scheme(manager, style)) {
+                auto name = gtk_source_style_scheme_get_name(scheme);
+                labels.emplace_back(name);
+            }
+            else {
+                labels.emplace_back(style);
+            }
+            values.emplace_back(style);
+        }
+        syntax->init("/theme/syntax-color-theme", labels, values, "");
+        _page_theme.add_line(false, _("Color theme:"), *syntax, "", _("Syntax coloring for XML dialog"), false);
+    }
+#endif
+    {
+        auto font_button = Gtk::make_managed<Gtk::Button>("...");
+        font_button->set_halign(Gtk::ALIGN_START);
+        auto font_box = Gtk::make_managed<Gtk::Entry>();
+        font_box->set_editable(false);
+        font_box->set_sensitive(false);
+        auto theme = INKSCAPE.themecontext;
+        font_box->set_text(theme->getMonospacedFont().to_string());
+        font_button->signal_clicked().connect([=](){
+            Gtk::FontChooserDialog dlg;
+            // show fixed-size fonts only
+            dlg.set_filter_func([](const Glib::RefPtr<const Pango::FontFamily>& family, const Glib::RefPtr<const Pango::FontFace>& face) {
+                return family && family->is_monospace();
+            });
+            dlg.set_font_desc(theme->getMonospacedFont());
+            dlg.set_position(Gtk::WIN_POS_MOUSE);
+            dlg.set_modal();
+            if (dlg.run() == Gtk::RESPONSE_OK) {
+                auto desc = dlg.get_font_desc();
+                theme->saveMonospacedFont(desc);
+                theme->adjustGlobalFontScale(theme->getFontScale() / 100);
+                font_box->set_text(desc.to_string());
+            }
+        });
+        _page_theme.add_line(false, _("Monospaced font:"), *font_box, "", _("Select fixed-width font"), true, font_button);
+
+        auto mono_font = Gtk::make_managed<UI::Widget::PrefCheckButton>();
+        mono_font->init( _("Use monospaced font"), "/dialogs/xml/mono-font", false);
+        _page_theme.add_line(false, _("XML tree:"), *mono_font, "", _("Use fixed-width font in XML dialog"), false);
+    }
+
+    //=======================================================================================================
 
     this->AddPage(_page_theme, _("Theming"), iter_ui, PREFS_PAGE_UI_THEME);
     symbolicThemeCheck();
diff --git a/src/ui/dialog/inkscape-preferences.h b/src/ui/dialog/inkscape-preferences.h
index 82141a32a5..9ed9f1cbc2 100644
--- a/src/ui/dialog/inkscape-preferences.h
+++ b/src/ui/dialog/inkscape-preferences.h
@@ -17,6 +17,7 @@
 #define INKSCAPE_UI_DIALOG_INKSCAPE_PREFERENCES_H
 
 // checking if cairo supports dithering
+#include <gtkmm/sizegroup.h>
 #ifdef  WITH_PATCHED_CAIRO
 #include "3rdparty/cairo/src/cairo.h"
 #else
diff --git a/src/ui/dialog/xml-tree.cpp b/src/ui/dialog/xml-tree.cpp
index 2dfad025cb..c14ce4fb26 100644
--- a/src/ui/dialog/xml-tree.cpp
+++ b/src/ui/dialog/xml-tree.cpp
@@ -11,6 +11,7 @@
  *   David Turner
  *   Jon A. Cruz <jon@joncruz.org>
  *   Abhishek Sharma
+ *   Mike Kowalski
  *
  * Copyright (C) 1999-2006 Authors
  * Released under GNU GPL v2+, read the file 'COPYING' for more information.
@@ -25,6 +26,7 @@
 #include <gtkmm/enums.h>
 #include <gtkmm/image.h>
 #include <gtkmm/menubutton.h>
+#include <gtkmm/object.h>
 #include <gtkmm/paned.h>
 #include <gtkmm/radiomenuitem.h>
 #include <gtkmm/scrolledwindow.h>
@@ -41,12 +43,15 @@
 #include "object/sp-root.h"
 #include "object/sp-string.h"
 
+#include "preferences.h"
 #include "ui/builder-utils.h"
 #include "ui/dialog-events.h"
 #include "ui/icon-loader.h"
 #include "ui/icon-names.h"
 #include "ui/tools/tool-base.h"
+#include "ui/syntax.h"
 
+#include "util/trim.h"
 #include "widgets/sp-xmlview-tree.h"
 
 namespace {
@@ -70,43 +75,44 @@ void paned_set_vertical(Gtk::Paned &paned, bool vertical)
 }
 } // namespace
 
-namespace Inkscape {
-namespace UI {
-namespace Dialog {
+namespace Inkscape::UI::Dialog {
 
 XmlTree::XmlTree()
-    : DialogBase("/dialogs/xml/", "XMLEditor"),
-    _builder(create_builder("dialog-xml.glade")),
-    _paned(get_widget<Gtk::Paned>(_builder, "pane")),
-    xml_element_new_button(get_widget<Gtk::Button>(_builder, "new-elem")),
-    xml_text_new_button(get_widget<Gtk::Button>(_builder, "new-text")),
-    xml_node_delete_button(get_widget<Gtk::Button>(_builder, "del")),
-    xml_node_duplicate_button(get_widget<Gtk::Button>(_builder, "dup")),
-    unindent_node_button(get_widget<Gtk::Button>(_builder, "unindent")),
-    indent_node_button(get_widget<Gtk::Button>(_builder, "indent")),
-    lower_node_button(get_widget<Gtk::Button>(_builder, "lower")),
-    raise_node_button(get_widget<Gtk::Button>(_builder, "raise"))
+    : DialogBase("/dialogs/xml/", "XMLEditor")
+    , _builder(create_builder("dialog-xml.glade"))
+    , _paned(get_widget<Gtk::Paned>(_builder, "pane"))
+    , xml_element_new_button(get_widget<Gtk::Button>(_builder, "new-elem"))
+    , xml_text_new_button(get_widget<Gtk::Button>(_builder, "new-text"))
+    , xml_node_delete_button(get_widget<Gtk::Button>(_builder, "del"))
+    , xml_node_duplicate_button(get_widget<Gtk::Button>(_builder, "dup"))
+    , unindent_node_button(get_widget<Gtk::Button>(_builder, "unindent"))
+    , indent_node_button(get_widget<Gtk::Button>(_builder, "indent"))
+    , lower_node_button(get_widget<Gtk::Button>(_builder, "lower"))
+    , raise_node_button(get_widget<Gtk::Button>(_builder, "raise"))
+    , _syntax_theme("/theme/syntax-color-theme")
+    , _mono_font("/dialogs/xml/mono-font", false)
 {
     /* tree view */
     tree = SP_XMLVIEW_TREE(sp_xmlview_tree_new(nullptr, nullptr, nullptr));
     gtk_widget_set_tooltip_text( GTK_WIDGET(tree), _("Drag to reorder nodes") );
 
     Gtk::ScrolledWindow& tree_scroller = get_widget<Gtk::ScrolledWindow>(_builder, "tree-wnd");
+    _treemm = Gtk::manage(Glib::wrap(GTK_WIDGET(tree)));
     tree_scroller.add(*Gtk::manage(Glib::wrap(GTK_WIDGET(tree))));
     fix_inner_scroll(&tree_scroller);
 
     Inkscape::Preferences *prefs = Inkscape::Preferences::get();
 
     /* attributes */
-    attributes = new AttrDialog();
+    attributes = Gtk::make_managed<AttrDialog>();
     attributes->set_margin_top(0);
     attributes->set_margin_bottom(0);
     attributes->set_margin_start(0);
     attributes->set_margin_end(0);
-    attributes->_scrolledWindow.set_shadow_type(Gtk::SHADOW_IN);
+    attributes->get_scrolled_window().set_shadow_type(Gtk::SHADOW_IN);
     attributes->show();
-    attributes->status_box.hide();
-    attributes->status_box.set_no_show_all();
+    attributes->get_status_box().hide();
+    attributes->get_status_box().set_no_show_all();
     _paned.pack2(*attributes, true, false);
 
     /* Signal handlers */
@@ -184,8 +190,7 @@ XmlTree::XmlTree()
         Glib::ustring icon = "layout-auto";
         if (layout == Horizontal) {
             icon = "layout-horizontal";
-        }
-        else if (layout == Vertical) {
+        } else if (layout == Vertical) {
             icon = "layout-vertical";
         }
         get_widget<Gtk::Image>(_builder, "layout-img").set_from_icon_name(icon + "-symbolic", Gtk::ICON_SIZE_SMALL_TOOLBAR);
@@ -207,6 +212,45 @@ XmlTree::XmlTree()
     _layout = static_cast<DialogLayout>(prefs->getIntLimited("/dialogs/xml/layout", Auto, Auto, Vertical));
     static_cast<Gtk::RadioMenuItem*>(menu_items.at(_layout))->set_active();
     set_layout(_layout);
+    // establish initial layout to prevent unwanted panels resize in auto layout mode
+    paned_set_vertical(_paned, true);
+
+    _syntax_theme.action = [=]() {
+        setSyntaxStyle(Inkscape::UI::Syntax::build_xml_styles(_syntax_theme));
+        // rebuild tree to change markup
+        rebuildTree();
+    };
+
+    setSyntaxStyle(Inkscape::UI::Syntax::build_xml_styles(_syntax_theme));
+
+    _mono_font.action = [=]() {
+        Glib::ustring mono("mono-font");
+        if (_mono_font) {
+            _treemm->get_style_context()->add_class(mono);
+        } else {
+            _treemm->get_style_context()->remove_class(mono);
+        }
+        attributes->set_mono_font(_mono_font);
+    };
+    _mono_font.action();
+
+    tree->renderer->signal_editing_canceled().connect([=]() {
+        stopNodeEditing(false, "", "");
+    });
+    tree->renderer->signal_edited().connect([=](const Glib::ustring& path, const Glib::ustring& name) {
+        stopNodeEditing(true, path, name);
+    });
+    tree->renderer->signal_editing_started().connect([=](Gtk::CellEditable* cell, const Glib::ustring& path) {
+        startNodeEditing(cell, path);
+    });
+}
+
+void XmlTree::rebuildTree()
+{
+    sp_xmlview_tree_set_repr(tree, nullptr);
+    if (auto document = getDocument()) {
+        set_tree_repr(document->getReprRoot());
+    }
 }
 
 void XmlTree::_resized()
@@ -226,8 +270,6 @@ void XmlTree::on_unrealize() {
     DialogBase::on_unrealize();
 }
 
-XmlTree::~XmlTree () { }
-
 void XmlTree::unsetDocument()
 {
     document_uri_set_connection.disconnect();
@@ -299,7 +341,7 @@ static void expand_parents(SPXMLViewTree *tree, Inkscape::XML::Node *repr)
     }
 }
 
-void XmlTree::set_tree_select(Inkscape::XML::Node *repr)
+void XmlTree::set_tree_select(Inkscape::XML::Node *repr, bool edit)
 {
     if (selected_repr) {
         Inkscape::GC::release(selected_repr);
@@ -326,7 +368,8 @@ void XmlTree::set_tree_select(Inkscape::XML::Node *repr)
             GtkTreePath* path = gtk_tree_model_get_path(GTK_TREE_MODEL(tree->store), &node);
             gtk_tree_view_scroll_to_cell(GTK_TREE_VIEW(tree), path, nullptr, TRUE, 0.66, 0.0);
             gtk_tree_selection_select_iter(selection, &node);
-            gtk_tree_view_set_cursor(GTK_TREE_VIEW(tree), path, NULL, false);
+            auto col = gtk_tree_view_get_column(&tree->tree, 0);
+            gtk_tree_view_set_cursor(GTK_TREE_VIEW(tree), path, edit ? col : nullptr, edit);
             gtk_tree_path_free(path);
 
         } else {
@@ -646,31 +689,82 @@ void XmlTree::cmd_new_element_node()
     if (!document)
         return;
 
-    Gtk::Dialog dialog;
-    Gtk::Entry entry;
-
-    dialog.get_content_area()->pack_start(entry);
-    dialog.add_button("Cancel", Gtk::RESPONSE_CANCEL);
-    dialog.add_button("Create", Gtk::RESPONSE_OK);
-    dialog.show_all();
-
-    int result = dialog.run();
-    if (result == Gtk::RESPONSE_OK) {
-        Glib::ustring new_name = entry.get_text();
-        if (!new_name.empty()) {
-            Inkscape::XML::Document *xml_doc = document->getReprDoc();
-            Inkscape::XML::Node *new_repr;
-            new_repr = xml_doc->createElement(new_name.c_str());
-            Inkscape::GC::release(new_repr);
-            selected_repr->appendChild(new_repr);
-            set_tree_select(new_repr);
-            set_dt_select(new_repr);
-
-            DocumentUndo::done(document, Q_("Undo History / XML dialog|Create new element node"), INKSCAPE_ICON("dialog-xml-editor"));
+    // enable in-place node name editing
+    tree->renderer->property_editable() = true;
+
+    auto dummy = ""; // this element has no corresponding SP* object and its construction is silent
+    auto xml_doc = document->getReprDoc();
+    _dummy = xml_doc->createElement(dummy); // create dummy placeholder so we can have a new temporary row in xml tree
+    _node_parent = selected_repr;   // remember where the node is inserted
+    selected_repr->appendChild(_dummy);
+    set_tree_select(_dummy, true); // enter in-place node name editing
+}
+
+void XmlTree::startNodeEditing(Gtk::CellEditable* cell, const Glib::ustring& path)
+{
+    if (!cell) {
+        return;
+    }
+    // remove dummy element name so user can start with an empty name
+    auto entry = dynamic_cast<Gtk::Entry *>(cell);
+    entry->get_buffer()->set_text("");
+}
+
+void XmlTree::stopNodeEditing(bool ok, const Glib::ustring& path, Glib::ustring element)
+{
+    tree->renderer->property_editable() = false;
+
+    auto document = getDocument();
+    if (!document) {
+        return;
+    }
+    // delete dummy node
+    if (_dummy) {
+        document->setXMLDialogSelectedObject(nullptr);
+
+        auto parent = _dummy->parent();
+        Inkscape::GC::release(_dummy);
+        sp_repr_unparent(_dummy);
+        if (parent) {
+            auto parentobject = document->getObjectByRepr(parent);
+            if (parentobject) {
+                parentobject->requestDisplayUpdate(SP_OBJECT_CHILD_MODIFIED_FLAG);
+            }
         }
+
+        _dummy = nullptr;
     }
-} // end of cmd_new_element_node()
 
+    Util::trim(element);
+    if (!ok || element.empty() || !_node_parent) {
+        return;
+    }
+
+    Inkscape::XML::Document* xml_doc = document->getReprDoc();
+    // Extract tag name
+    {
+        static auto const extract_tagname = Glib::Regex::create("^<?\\s*(\\w[\\w:\\-\\d]*)");
+        Glib::MatchInfo match_info;
+        extract_tagname->match(element, match_info);
+        if (!match_info.matches()) {
+            return;
+        }
+        element = match_info.fetch(1);
+    }
+
+    // prepend "svg:" namespace if none is given
+    if (element.find(':') == Glib::ustring::npos) {
+        element = "svg:" + element;
+    }
+    auto repr = xml_doc->createElement(element.c_str());
+    Inkscape::GC::release(repr);
+    _node_parent->appendChild(repr);
+    set_dt_select(repr);
+    set_tree_select(repr, true);
+    _node_parent = nullptr;
+
+    DocumentUndo::done(document, Q_("Undo History / XML dialog|Create new element node"), INKSCAPE_ICON("dialog-xml-editor"));
+}
 
 void XmlTree::cmd_new_text_node()
 {
@@ -876,9 +970,12 @@ void XmlTree::desktopReplaced() {
     }
 }
 
+void XmlTree::setSyntaxStyle(Inkscape::UI::Syntax::XMLStyles const &new_style)
+{
+    tree->formatter->setStyle(new_style);
 }
-}
-}
+
+} // namespace Inkscape::UI::Dialog
 
 /*
   Local Variables:
diff --git a/src/ui/dialog/xml-tree.h b/src/ui/dialog/xml-tree.h
index b56739e679..2389c6fdb8 100644
--- a/src/ui/dialog/xml-tree.h
+++ b/src/ui/dialog/xml-tree.h
@@ -13,6 +13,9 @@
 #ifndef INKSCAPE_UI_DIALOG_XML_TREE_H
 #define INKSCAPE_UI_DIALOG_XML_TREE_H
 
+#include <glibmm/ustring.h>
+#include <gtkmm/treeview.h>
+#include <gtkmm/widget.h>
 #include <memory>
 #include <glibmm/refptr.h>
 #include <gtkmm/builder.h>
@@ -29,6 +32,8 @@
 #include "message.h"
 #include "attrdialog.h"
 #include "dialog-base.h"
+#include "preferences.h"
+#include "ui/syntax.h"
 
 class SPObject;
 struct SPXMLViewAttrList;
@@ -51,7 +56,9 @@ class XmlTree : public DialogBase
 {
 public:
     XmlTree();
-    ~XmlTree() override;
+    ~XmlTree() override = default;
+
+    void setSyntaxStyle(Inkscape::UI::Syntax::XMLStyles const &new_style);
 
 private:
     void unsetDocument();
@@ -77,7 +84,7 @@ private:
     /**
      * Select a node in the xml tree
      */
-    void set_tree_select(Inkscape::XML::Node *repr);
+    void set_tree_select(Inkscape::XML::Node *repr, bool edit = false);
 
     /**
      * Set the attribute list to match the selected node in the tree
@@ -146,6 +153,9 @@ private:
     bool in_dt_coordsys(SPObject const &item);
 
     void on_unrealize() override;
+    void rebuildTree();
+    void stopNodeEditing(bool ok, Glib::ustring const &path, Glib::ustring name);
+    void startNodeEditing(Gtk::CellEditable *cell, Glib::ustring const &path);
 
     /**
      * Flag to ensure only one operation is performed at once
@@ -161,6 +171,7 @@ private:
 
     /* XmlTree Widgets */
     SPXMLViewTree *tree = nullptr;
+    Gtk::Widget* _treemm = nullptr;
     AttrDialog *attributes;
     Gtk::Box *_attrbox;
 
@@ -186,6 +197,10 @@ private:
     gulong _tree_move = 0;
     enum DialogLayout: int { Auto = 0, Horizontal, Vertical };
     DialogLayout _layout = Auto;
+    Pref<Glib::ustring> _syntax_theme;
+    Pref<bool> _mono_font;
+    Inkscape::XML::Node* _dummy = nullptr;
+    Inkscape::XML::Node* _node_parent = nullptr;
 };
 
 } // namespace Dialog
diff --git a/src/ui/icon-loader.cpp b/src/ui/icon-loader.cpp
index f524028ce2..a5361621a5 100644
--- a/src/ui/icon-loader.cpp
+++ b/src/ui/icon-loader.cpp
@@ -116,6 +116,11 @@ Glib::RefPtr<Gdk::Pixbuf> sp_get_shape_icon(Glib::ustring shape_type, Gdk::RGBA
 
     Gtk::IconInfo iconinfo = icon_theme->lookup_icon("shape-" + shape_type + "-symbolic",
                                                      size * scale, Gtk::ICON_LOOKUP_FORCE_SIZE);
+    if (!iconinfo) {
+        // fallback to regular icons
+        iconinfo = icon_theme->lookup_icon(shape_type + "-symbolic", size * scale, Gtk::ICON_LOOKUP_FORCE_SIZE);
+    }
+
     if (!iconinfo) {
         iconinfo = icon_theme->lookup_icon("shape-unknown-symbolic", size * scale, Gtk::ICON_LOOKUP_FORCE_SIZE);
         // We know this could fail, but it should exist, so persist.
diff --git a/src/ui/shortcuts.cpp b/src/ui/shortcuts.cpp
index 574a42bb11..07758c9ac8 100644
--- a/src/ui/shortcuts.cpp
+++ b/src/ui/shortcuts.cpp
@@ -487,8 +487,8 @@ Shortcuts::add_shortcut(Glib::ustring name, const Gtk::AccelKey& shortcut, bool
 {
     // Remove previous use of shortcut (already removed if new user shortcut).
     if (Glib::ustring old_name = remove_shortcut(shortcut); old_name != "") {
-        std::cerr << "Shortcut::add_shortcut: duplicate shortcut found for: " << shortcut.get_abbrev().raw()
-                  << "  Old: " << old_name.raw() << "  New: " << name.raw() << " !" << std::endl;
+        // std::cerr << "Shortcut::add_shortcut: duplicate shortcut found for: " << shortcut.get_abbrev().raw()
+                //   << "  Old: " << old_name.raw() << "  New: " << name.raw() << " !" << std::endl;
     }
 
     // Add shortcut
diff --git a/src/ui/syntax.cpp b/src/ui/syntax.cpp
new file mode 100644
index 0000000000..b802d7d0cd
--- /dev/null
+++ b/src/ui/syntax.cpp
@@ -0,0 +1,395 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/** @file Syntax coloring via Gtksourceview and Pango markup.
+ */
+/* Authors:
+ *   Rafael Siejakowski <rs@rs-math.net>
+ *   Mike Kowalski
+ *
+ * Copyright (C) 2022 Authors
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#include "ui/syntax.h"
+
+#include <glibmm/ustring.h>
+#include <pango/pango-attributes.h>
+#include <sstream>
+#include <stdexcept>
+
+#include "color.h"
+#include "config.h"
+#include "io/resource.h"
+#include "object/sp-factory.h"
+#include "util/trim.h"
+
+#if WITH_GSOURCEVIEW
+#   include <gtksourceview/gtksource.h>
+#endif
+
+namespace Inkscape::UI::Syntax {
+
+Glib::ustring XMLFormatter::_format(Style const &style, Glib::ustring const &content) const
+{
+    return _format(style, content.c_str());
+}
+
+/** Get the opening tag of the Pango markup for this style. */
+Glib::ustring Style::openingTag() const
+{
+    if (isDefault()) {
+        return "";
+    }
+
+    std::ostringstream ost;
+    ost << "<span";
+    if (color) {
+        ost << " color=\"" << color->raw() << '"';
+    }
+    if (background) {
+        ost << " bgcolor=\"" << background->raw() << '"';
+    }
+    if (bold) {
+        ost << " weight=\"bold\"";
+    }
+    if (italic) {
+        ost << " font_style=\"italic\"";
+    }
+    if (underline) {
+        ost << " underline=\"single\"";
+    }
+
+    ost << ">";
+    return Glib::ustring(ost.str());
+}
+
+/** Get the closing tag of Pango markup for this style. */
+Glib::ustring Style::closingTag() const
+{
+    return isDefault() ? "" : "</span>";
+}
+
+Glib::ustring quote(const char* text)
+{
+    return Glib::ustring::compose("\"%1\"", text);
+}
+
+/** Open a new XML tag with the given tag name. */
+void XMLFormatter::openTag(char const *tag_name)
+{
+    _wip = _format(_style.angular_brackets, "<");
+
+    // Highlight as errors unsupported tags in SVG namespace (explicit or implicit).
+    bool error = false;
+    std::string fully_qualified_name(tag_name);
+    if (fully_qualified_name.empty()) {
+        return;
+    }
+    bool is_svg = false;
+    if (fully_qualified_name.find(':') == std::string::npos) {
+        fully_qualified_name = std::string("svg:") + fully_qualified_name;
+        is_svg = true;
+    } else if (fully_qualified_name.find("svg:") == 0) {
+        is_svg = true;
+    }
+    if (is_svg && !SPFactory::supportsType(fully_qualified_name)) {
+        error = true;
+    }
+    _wip += _format(error ? _style.error : _style.tag_name, tag_name);
+}
+
+void XMLFormatter::addAttribute(char const *name, char const *value)
+{
+    _wip += Glib::ustring::compose(" %1%2%3",
+                                   _format(_style.attribute_name, name),
+                                   _format(_style.angular_brackets, "="),
+                                   _format(_style.attribute_value, quote(value)));
+}
+
+Glib::ustring XMLFormatter::finishTag(bool self_close)
+{
+    return _wip + _format(_style.angular_brackets, self_close ? "/>" : ">");
+}
+
+Glib::ustring XMLFormatter::formatContent(char const* content, bool wrap_in_quotes) const
+{
+    Glib::ustring text = wrap_in_quotes ? quote(content) : content;
+    return _format(_style.content, text);
+}
+
+Glib::ustring XMLFormatter::formatComment(char const* comment, bool wrap_in_marks) const
+{
+    if (wrap_in_marks) {
+        auto wrapped = Glib::ustring::compose("<!--%1-->", comment);
+        return _format(_style.comment, wrapped.c_str());
+    }
+    return _format(_style.comment, comment);
+}
+
+XMLStyles build_xml_styles(const Glib::ustring& syntax_theme)
+{
+    XMLStyles styles;
+
+#if WITH_GSOURCEVIEW
+    auto manager = gtk_source_style_scheme_manager_get_default();
+    if (auto scheme = gtk_source_style_scheme_manager_get_scheme(manager, syntax_theme.c_str())) {
+
+        auto get_color = [](GtkSourceStyle* style, const char* prop) -> std::optional<Glib::ustring> {
+            std::optional<Glib::ustring> maybe_color;
+            Glib::ustring name(prop);
+            gboolean set;
+            gchar* color = 0;
+            g_object_get(style, (name + "-set").c_str(), &set, name.c_str(), &color, nullptr);
+            if (set && color && *color == '#') {
+                maybe_color = Glib::ustring(color);
+            }
+            g_free(color);
+            return maybe_color;
+        };
+
+        auto get_bool = [](GtkSourceStyle* style, const char* prop, bool def = false) -> bool {
+            Glib::ustring name(prop);
+            gboolean set;
+            gboolean flag;
+            g_object_get(style, (name + "-set").c_str(), &set, name.c_str(), &flag, nullptr);
+            return set ? !!flag : def;
+        };
+
+        auto get_underline = [](GtkSourceStyle* style, bool def = false) -> bool {
+            Glib::ustring name("underline");
+            gboolean set;
+            PangoUnderline underline;
+            g_object_get(style, (name + "-set").c_str(), &set, ("pango-" + name).c_str(), &underline, nullptr);
+            return set ? underline != PANGO_UNDERLINE_NONE : def;
+        };
+
+        auto to_style = [&](char const *id) -> Style {
+            auto s = gtk_source_style_scheme_get_style(scheme, id);
+            if (!s) {
+                return Style();
+            }
+
+            Style style;
+
+            style.color      = get_color(s, "foreground");
+            style.background = get_color(s, "background");
+            style.bold       = get_bool(s, "bold");
+            style.italic     = get_bool(s, "italic");
+            style.underline  = get_underline(s);
+
+            return style;
+        };
+
+        styles.tag_name         = to_style("def:statement");
+        styles.attribute_name   = to_style("def:number");
+        styles.attribute_value  = to_style("def:string");
+        styles.content          = to_style("def:string");
+        styles.comment          = to_style("def:comment");
+        styles.prolog           = to_style("def:warning");
+        styles.angular_brackets = to_style("draw-spaces");
+        styles.error            = to_style("def:error");
+    }
+#endif
+
+    return styles;
+}
+
+/** @brief Reformat CSS for better readability.
+ */
+Glib::ustring prettify_css(Glib::ustring const &css)
+{
+    // Ensure that there's a space after every colon, unless there's a slash (as in a URL).
+    static auto const colon_without_space = Glib::Regex::create(":([^\\s\\/])");
+    auto reformatted = colon_without_space->replace(css, 0, ": \\1", Glib::RegexMatchFlags::REGEX_MATCH_NOTEMPTY);
+    // Ensure that there's a newline after every semicolon.
+    static auto const semicolon_without_newline = Glib::Regex::create(";([^\r\n])");
+    reformatted = semicolon_without_newline->replace(reformatted, 0, ";\n\\1", Glib::RegexMatchFlags::REGEX_MATCH_NEWLINE_ANYCRLF);
+    // If the last character is not a semicolon, append one.
+    if (auto len = css.size(); len && css[len - 1] != ';') {
+        reformatted += ";";
+    }
+    return reformatted;
+}
+
+/** Undo the CSS prettification by stripping some whitespace from CSS markup. */
+Glib::ustring minify_css(Glib::ustring const &css)
+{
+    static auto const space_after = Glib::Regex::create("(:|;)[\\s]+");
+    auto minified = space_after->replace(css, 0, "\\1", Glib::RegexMatchFlags::REGEX_MATCH_NEWLINE_ANY);
+    // Strip final semicolon
+    if (auto const len = minified.size(); len && minified[len - 1] == ';') {
+        minified = minified.erase(len - 1);
+    }
+    return minified;
+}
+
+/** @brief Reformat a path 'd' attibute for better readability. */
+Glib::ustring prettify_svgd(Glib::ustring const &d)
+{
+    auto result = d;
+    Util::trim(result);
+    // Ensure that a non-M command is preceded only by a newline.
+    static auto const space_b4_command = Glib::Regex::create("(?<=\\S)\\s*(?=[LHVCSQTAZlhvcsqtaz])");
+    result = space_b4_command->replace(result, 1, "\n", Glib::RegexMatchFlags::REGEX_MATCH_NEWLINE_ANY);
+
+    // Before a non-initial M command, we want to have two newlines to visually separate the subpaths.
+    static auto const space_b4_m = Glib::Regex::create("(?<=\\S)\\s*(?=[Mm])");
+    result = space_b4_m->replace(result, 1, "\n\n", Glib::RegexMatchFlags::REGEX_MATCH_NEWLINE_ANY);
+
+    // Ensure that there's a space after each command letter other than Z.
+    static auto const nospace = Glib::Regex::create("([MLHVCSQTAmlhvcsqta])(?=\\S)");
+    return nospace->replace(result, 0, "\\1 ", Glib::RegexMatchFlags::REGEX_MATCH_NEWLINE_ANY);
+}
+
+/** @brief Remove excessive space, including newlines, from a path 'd' attibute. */
+Glib::ustring minify_svgd(Glib::ustring const &d)
+{
+    static auto const excessive_space = Glib::Regex::create("[\\s]+");
+    auto result = excessive_space->replace(d, 0, " ", Glib::RegexMatchFlags::REGEX_MATCH_NEWLINE_ANY);
+    Util::trim(result);
+    return result;
+}
+
+/** Set default options on a TextView widget used for syntax-colored editing. */
+static void init_text_view(Gtk::TextView* textview)
+{
+    textview->set_wrap_mode(Gtk::WrapMode::WRAP_WORD);
+    textview->set_editable(true);
+    textview->show();
+}
+
+/// Plain text view widget without syntax coloring
+class PlainTextView : public TextEditView
+{
+public:
+    PlainTextView()
+        : _textview(std::make_unique<Gtk::TextView>(Gtk::TextBuffer::create()))
+    {
+        init_text_view(_textview.get());
+    }
+
+    void setStyle(const Glib::ustring& theme) override { /* no op */ }
+    void setText(const Glib::ustring& text) override { _textview->get_buffer()->set_text(text); }
+
+    Glib::ustring getText() const override { return _textview->get_buffer()->get_text(); }
+    Gtk::TextView& getTextView() const override { return *_textview; }
+
+private:
+    std::unique_ptr<Gtk::TextView> _textview;
+};
+
+#if WITH_GSOURCEVIEW
+
+/** @brief Return a pointer to a language manager which is aware of both
+ * default and custom syntaxes.
+ */
+static GtkSourceLanguageManager* get_language_manager()
+{
+    auto ui_path = IO::Resource::get_path_string(IO::Resource::SYSTEM, IO::Resource::UIS);
+    auto default_manager = gtk_source_language_manager_get_default();
+    auto default_paths = gtk_source_language_manager_get_search_path(default_manager);
+
+    std::vector<char const *> all_paths;
+    for (auto path = default_paths; *path; path++) {
+        all_paths.push_back(*path);
+    }
+    all_paths.push_back(ui_path.c_str());
+    all_paths.push_back(nullptr);
+
+    auto result = gtk_source_language_manager_new();
+    gtk_source_language_manager_set_search_path(result, (gchar **)all_paths.data());
+    return result;
+}
+
+class SyntaxHighlighting : public TextEditView
+{
+public:
+    SyntaxHighlighting() = delete;
+    /** @brief Construct a syntax highlighter for a given language. */
+    SyntaxHighlighting(char const* const language,
+                       Glib::ustring (*prettify_func)(Glib::ustring const &),
+                       Glib::ustring (*minify_func)(Glib::ustring const &))
+        : _prettify{prettify_func}
+        , _minify{minify_func}
+    {
+        auto manager = get_language_manager();
+        auto lang = gtk_source_language_manager_get_language(manager, language);
+        _buffer = gtk_source_buffer_new_with_language(lang);
+        auto view = gtk_source_view_new_with_buffer(_buffer);
+        _textview = std::unique_ptr<Gtk::TextView>(Glib::wrap((GtkTextView*)view));
+        if (!_textview) {
+            // don't crash when sourceview cannot be created; substitute with a regular one;
+            // in this case GTK has already outputted warnings
+            _textview = std::make_unique<Gtk::TextView>(Gtk::TextBuffer::create());
+        }
+        init_text_view(_textview.get());
+    }
+
+    ~SyntaxHighlighting() override { g_object_unref(_buffer); }
+private:
+    GtkSourceBuffer *_buffer = nullptr; // Owned by us
+    std::unique_ptr<Gtk::TextView> _textview;
+    Glib::ustring (*_prettify)(Glib::ustring const &);
+    Glib::ustring (*_minify)(Glib::ustring const &);
+
+public:
+    void setStyle(Glib::ustring const &theme) override
+    {
+        auto manager = gtk_source_style_scheme_manager_get_default();
+        auto scheme = gtk_source_style_scheme_manager_get_scheme(manager, theme.c_str());
+        gtk_source_buffer_set_style_scheme(_buffer, scheme);
+    }
+
+    /** @brief Set the displayed text to a prettified version of the passed string. */
+    void setText(Glib::ustring const &text) override
+    {
+        _textview->get_buffer()->set_text(_prettify(text));
+    }
+
+    /** @brief Get a minified version of the buffer contents, suitable for inserting into XML. */
+    Glib::ustring getText() const override
+    {
+        return _minify(_textview->get_buffer()->get_text());
+    }
+
+    Gtk::TextView &getTextView() const override { return *_textview; };
+};
+
+#endif // WITH_GSOURCEVIEW
+
+/** Create a styled text view using the desired syntax highlighting mode. */
+std::unique_ptr<TextEditView> TextEditView::create(SyntaxMode mode)
+{
+#if WITH_GSOURCEVIEW
+    auto const no_reformat = [](auto &s) { return s; };
+    switch (mode) {
+        case SyntaxMode::PlainText:
+            return std::make_unique<PlainTextView>();
+        case SyntaxMode::InlineCss:
+            return std::make_unique<SyntaxHighlighting>("inline-css", &prettify_css, &minify_css);
+        case SyntaxMode::CssStyle:
+            return std::make_unique<SyntaxHighlighting>("css", no_reformat, no_reformat);
+        case SyntaxMode::SvgPathData:
+            return std::make_unique<SyntaxHighlighting>("svgd", &prettify_svgd, &minify_svgd);
+        case SyntaxMode::SvgPolyPoints:
+            return std::make_unique<SyntaxHighlighting>("svgpoints", no_reformat, no_reformat);
+        default:
+            throw std::runtime_error("Missing case statement in TetxEditView::create()");
+    }
+#else
+    return std::make_unique<PlainTextView>();
+#endif
+}
+
+} // namespace Inkscape::UI::Syntax
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :
diff --git a/src/ui/syntax.h b/src/ui/syntax.h
new file mode 100644
index 0000000000..528ad93281
--- /dev/null
+++ b/src/ui/syntax.h
@@ -0,0 +1,134 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/** @file Syntax coloring via Gtksourceview and Pango markup.
+ */
+/* Authors:
+ *   Rafael Siejakowski <rs@rs-math.net>
+ *
+ * Copyright (C) 2022 Authors
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#ifndef SEEN_UI_UI_SYNTAX_H
+#define SEEN_UI_UI_SYNTAX_H
+
+#include <memory>
+#include <optional>
+#include <vector>
+#include <gtkmm/textview.h>
+#include <glibmm.h>
+#include <glibmm/ustring.h>
+
+#include "color.h"
+
+namespace Inkscape::UI::Syntax {
+
+/** The style of a single element in a (Pango markup)-enabled widget. */
+struct Style
+{
+    std::optional<Glib::ustring> color;
+    std::optional<Glib::ustring> background;
+    uint8_t bold      : 1;
+    uint8_t italic    : 1;
+    uint8_t underline : 1;
+
+    Style()
+        : bold{false}
+        , italic{false}
+        , underline{false}
+    {}
+
+    bool isDefault() const { return !color && !background && !bold && !italic && !underline; }
+    Glib::ustring openingTag() const;
+    Glib::ustring closingTag() const;
+};
+
+/** The styles used for simple XML syntax highlighting. */
+struct XMLStyles
+{
+    Style prolog;
+    Style comment;
+    Style angular_brackets;
+    Style tag_name;
+    Style attribute_name;
+    Style attribute_value;
+    Style content;
+    Style error;
+};
+
+/** @brief A formatter for XML syntax, based on Pango markup.
+ *
+ * This mechanism is used in the TreeView in the XML Dialog,
+ * where the syntax highlighting of XML tags is accomplished
+ * via Pango markup.
+ */
+class XMLFormatter
+{
+public:
+    XMLFormatter() = default;
+    XMLFormatter(XMLStyles &&styles)
+        : _style{styles}
+    {}
+
+    void setStyle(XMLStyles const &new_style) { _style = new_style; }
+    void setStyle(XMLStyles &&new_style) { _style = new_style; }
+
+    void openTag(char const *tag_name);
+    void addAttribute(char const *attribute_name, char const *attribute_value);
+    Glib::ustring finishTag(bool self_close = false);
+
+    Glib::ustring formatContent(char const* content, bool wrap_in_quotes = true) const;
+    Glib::ustring formatComment(char const* comment, bool wrap_in_comment_marks = true) const;
+    Glib::ustring formatProlog(char const* prolog) const { return _format(_style.prolog, prolog); }
+
+private:
+    Glib::ustring _format(Style const &style, Glib::ustring const &content) const;
+    Glib::ustring _format(Style const &style, char const *content) const
+    {
+        return style.openingTag() + Glib::Markup::escape_text(content) + style.closingTag();
+    }
+
+    XMLStyles _style;
+    Glib::ustring _wip;
+};
+
+/// Build XML styles from a GTKSourceView syntax color theme.
+XMLStyles build_xml_styles(const Glib::ustring& syntax_theme);
+
+/// Syntax highlighting mode (language).
+enum class SyntaxMode
+{
+    PlainText,     ///< Plain text (no highlighting).
+    InlineCss,     ///< Inline CSS (contents of a style="..." attribute).
+    CssStyle,      ///< File-scope CSS (contents of a CSS file or a <style> tag).
+    SvgPathData,   ///< Contents of the 'd' attribute of the SVG <path> element.
+    SvgPolyPoints  ///< Contents of the 'points' attribute of <polyline> or <polygon>.
+};
+
+/// Base class for styled text editing widget.
+class TextEditView
+{
+public:
+    virtual ~TextEditView() = default;
+    virtual void setStyle(const Glib::ustring& theme) = 0;
+    virtual void setText(const Glib::ustring& text) = 0;
+    virtual Glib::ustring getText() const = 0;
+    virtual Gtk::TextView& getTextView() const = 0;
+
+    static std::unique_ptr<TextEditView> create(SyntaxMode mode);
+};
+
+} // namespace Inkscape::UI::Syntax
+
+#endif // SEEN_UI_UI_SYNTAX_H
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :
diff --git a/src/ui/themes.cpp b/src/ui/themes.cpp
index bb58245755..4e082662d6 100644
--- a/src/ui/themes.cpp
+++ b/src/ui/themes.cpp
@@ -16,16 +16,25 @@
 #include "preferences.h"
 #include "io/resource.h"
 #include "svg/svg-color.h"
+#include <cstddef>
 #include <cstring>
 #include <gio/gio.h>
 #include <glibmm.h>
+#include <glibmm/ustring.h>
 #include <gtkmm.h>
 #include <map>
+#include <pangomm/font.h>
+#include <pangomm/fontdescription.h>
 #include <utility>
 #include <vector>
 #include <regex>
 #include "svg/css-ostringstream.h"
 
+#include "config.h"
+#if WITH_GSOURCEVIEW
+#   include <gtksourceview/gtksource.h>
+#endif
+
 namespace Inkscape {
 namespace UI {
 
@@ -513,7 +522,7 @@ std::vector<guint32> ThemeContext::getHighlightColors(Gtk::Window *window)
     return colors;
 }
 
-void ThemeContext::adjust_global_font_scale(double factor) {
+void ThemeContext::adjustGlobalFontScale(double factor) {
     if (factor < 0.1 || factor > 10) {
         g_warning("Invalid font scaling factor %f in ThemeContext::adjust_global_font_scale", factor);
         return;
@@ -524,13 +533,73 @@ void ThemeContext::adjust_global_font_scale(double factor) {
 
     Inkscape::CSSOStringStream os;
     os.precision(3);
-    os << "widget, menuitem, popover { font-size: " << factor << "rem; }";
+    os << "widget, menuitem, popover { font-size: " << factor << "rem; }\n";
+
+    os << ".mono-font {";
+    auto desc = getMonospacedFont();
+    os << "font-family: " << desc.get_family() << ";";
+    switch (desc.get_style()) {
+        case Pango::STYLE_ITALIC:
+            os << "font-style: italic;";
+            break;
+        case Pango::STYLE_OBLIQUE:
+            os << "font-style: oblique;";
+            break;
+    }
+    os << "font-weight: " << static_cast<int>(desc.get_weight()) << ";";
+    double size = desc.get_size();
+    os << "font-size: " << factor * (desc.get_size_is_absolute() ? size : size / Pango::SCALE) << "px;";
+    os << "}";
+
     _fontsizeprovider->load_from_data(os.str());
 
     // note: priority set to APP - 1 to make sure styles.css take precedence over generic font-size
     Gtk::StyleContext::add_provider_for_screen(screen, _fontsizeprovider, GTK_STYLE_PROVIDER_PRIORITY_APPLICATION - 1);
 }
 
+void ThemeContext::initialize_source_syntax_styles() {
+#if WITH_GSOURCEVIEW
+    auto manager = gtk_source_style_scheme_manager_get_default();
+    // to reset path: gtk_source_style_scheme_manager_set_search_path(manager, nullptr);
+    auto themes = IO::Resource::get_path_string(IO::Resource::SYSTEM, IO::Resource::UIS, "syntax-themes");
+    gtk_source_style_scheme_manager_prepend_search_path(manager, themes.c_str());
+#endif
+}
+
+void ThemeContext::select_default_syntax_style(bool dark_theme)
+{
+#if WITH_GSOURCEVIEW
+    auto prefs = Inkscape::Preferences::get();
+    auto default_theme = prefs->getString("/theme/syntax-color-theme");
+    auto light = "inkscape-light";
+    auto dark = "inkscape-dark";
+    if (default_theme.empty() || default_theme == light || default_theme == dark) {
+        prefs->setString("/theme/syntax-color-theme", dark_theme ? dark : light);
+    }
+#endif
+}
+
+void ThemeContext::saveMonospacedFont(Pango::FontDescription desc)
+{
+    Preferences::get()->setString(get_monospaced_font_pref_path(), desc.to_string());
+}
+
+Pango::FontDescription ThemeContext::getMonospacedFont() const
+{
+    auto font = Preferences::get()->getString(get_monospaced_font_pref_path(), "Monospace 13");
+    return Pango::FontDescription(font);
+}
+
+double ThemeContext::getFontScale() const
+{
+    return Preferences::get()->getDoubleLimited(get_font_scale_pref_path(), 100.0, 10.0, 500.0);
+}
+
+void ThemeContext::saveFontScale(double scale)
+{
+    Preferences::get()->setDouble(get_font_scale_pref_path(), scale);
+}
+
 } // UI
 } // Inkscape
 
diff --git a/src/ui/themes.h b/src/ui/themes.h
index a99cd3ea13..9a742cbaa4 100644
--- a/src/ui/themes.h
+++ b/src/ui/themes.h
@@ -16,8 +16,10 @@
 
 #include <cstring>
 #include <glibmm.h>
+#include <glibmm/ustring.h>
 #include <gtkmm.h>
 #include <map>
+#include <pangomm/fontdescription.h>
 #include <utility>
 #include <vector>
 #include <sigc++/signal.h>
@@ -36,28 +38,41 @@ typedef std::map<Glib::ustring, bool> gtkThemeList;
 class ThemeContext
 {
 public:
-ThemeContext();
-~ThemeContext() = default;
-// Name of theme -> has dark theme
-typedef std::map<Glib::ustring, bool> gtkThemeList;
-void inkscape_fill_gtk(const gchar *path, gtkThemeList &themes);
-std::map<Glib::ustring, bool> get_available_themes();
-void add_gtk_css(bool only_providers, bool cached = false);
-void add_icon_theme();
-Glib::ustring get_symbolic_colors();
-Glib::RefPtr<Gtk::CssProvider> getColorizeProvider() { return _colorizeprovider;}
-Glib::RefPtr<Gtk::CssProvider> getContrastThemeProvider() { return _contrastthemeprovider;}
-Glib::RefPtr<Gtk::CssProvider> getThemeProvider() { return _themeprovider;}
-Glib::RefPtr<Gtk::CssProvider> getStyleProvider() { return _styleprovider;}
-sigc::signal<void ()> getChangeThemeSignal() { return _signal_change_theme;}
-// set application-wide font size adjustment by a factor, where 1 is 100% (no change)
-void adjust_global_font_scale(double factor);
+    ThemeContext();
+    ~ThemeContext() = default;
+    // Name of theme -> has dark theme
+    typedef std::map<Glib::ustring, bool> gtkThemeList;
+    void inkscape_fill_gtk(const gchar *path, gtkThemeList &themes);
+    std::map<Glib::ustring, bool> get_available_themes();
+    void add_gtk_css(bool only_providers, bool cached = false);
+    void add_icon_theme();
+    Glib::ustring get_symbolic_colors();
+    Glib::RefPtr<Gtk::CssProvider> getColorizeProvider() { return _colorizeprovider;}
+    Glib::RefPtr<Gtk::CssProvider> getContrastThemeProvider() { return _contrastthemeprovider;}
+    Glib::RefPtr<Gtk::CssProvider> getThemeProvider() { return _themeprovider;}
+    Glib::RefPtr<Gtk::CssProvider> getStyleProvider() { return _styleprovider;}
+    sigc::signal<void ()> getChangeThemeSignal() { return _signal_change_theme;}
+    /// Set application-wide font size adjustment by a factor, where 1 is 100% (no change)
+    void adjustGlobalFontScale(double factor);
+    /// Get current font scaling factor (50 - 150, percent of "normal" size)
+    double getFontScale() const;
+    /// Save font scaling factor in preferences
+    void saveFontScale(double scale);
+    static Glib::ustring get_font_scale_pref_path() { return "/theme/fontscale"; }
+
+    /// User-selected monospaced font used by XML dialog and attribute editor
+    Pango::FontDescription getMonospacedFont() const;
+    void saveMonospacedFont(Pango::FontDescription desc);
+    static Glib::ustring get_monospaced_font_pref_path() { return "/ui/mono-font/desc"; }
 
-// True if current theme (applied one) is dark
-bool isCurrentThemeDark(Gtk::Container *window);
+    // True if current theme (applied one) is dark
+    bool isCurrentThemeDark(Gtk::Container *window);
 
 static std::vector<guint32> getHighlightColors(Gtk::Window *window);
 
+    static void initialize_source_syntax_styles();
+    static void select_default_syntax_style(bool dark_theme);
+
 private:
     // user change theme
     sigc::signal<void ()> _signal_change_theme;
@@ -67,7 +82,7 @@ private:
     Glib::RefPtr<Gtk::CssProvider> _colorizeprovider;
     Glib::RefPtr<Gtk::CssProvider> _spinbuttonprovider;
 #if __APPLE__
-  Glib::RefPtr<Gtk::CssProvider> _macstyleprovider;
+    Glib::RefPtr<Gtk::CssProvider> _macstyleprovider;
 #endif
     std::unique_ptr<Preferences::Observer> _spinbutton_observer;
     Glib::RefPtr<Gtk::CssProvider> _fontsizeprovider = Gtk::CssProvider::create();
diff --git a/src/ui/util.cpp b/src/ui/util.cpp
index 4fa2e087a4..66cce8b5a8 100644
--- a/src/ui/util.cpp
+++ b/src/ui/util.cpp
@@ -16,7 +16,10 @@
 #include <cstdint>
 #include <gdkmm/rgba.h>
 #include <gtkmm.h>
+#include <gtkmm/cellrenderer.h>
+#include <gtkmm/enums.h>
 #include <stdexcept>
+#include <tuple>
 
 /**
  * Recursively look through pre-constructed widget parents for a specific named widget.
@@ -74,8 +77,8 @@ bool is_widget_effectively_visible(Gtk::Widget const *widget) {
     return widget->get_child_visible();
 }
 
-namespace Inkscape {
-namespace UI {
+namespace Inkscape::UI {
+
 void resize_widget_children(Gtk::Widget *widget) {
     if(widget) {
         Gtk::Allocation allocation;
@@ -84,8 +87,27 @@ void resize_widget_children(Gtk::Widget *widget) {
         widget->size_allocate(allocation, baseline);
     }
 }
+
+Gtk::StateFlags cell_flags_to_state_flags(Gtk::CellRendererState state)
+{
+    auto flags = Gtk::STATE_FLAG_NORMAL;
+
+    for (auto [s, f]: (std::tuple<Gtk::CellRendererState, Gtk::StateFlags>[]) {
+        {Gtk::CELL_RENDERER_SELECTED, Gtk::STATE_FLAG_SELECTED},
+        {Gtk::CELL_RENDERER_PRELIT, Gtk::STATE_FLAG_PRELIGHT},
+        {Gtk::CELL_RENDERER_INSENSITIVE, Gtk::STATE_FLAG_INSENSITIVE},
+        {Gtk::CELL_RENDERER_FOCUSED, Gtk::STATE_FLAG_FOCUSED},
+    })
+    {
+        if (state & s) {
+            flags |= f;
+        }
+    }
+
+    return flags;
 }
-}
+
+} // namespace Inkscape::UI
 
 Gdk::RGBA mix_colors(const Gdk::RGBA& a, const Gdk::RGBA& b, float ratio) {
     auto lerp = [](double v0, double v1, double t){ return (1.0 - t) * v0 + t * v1; };
diff --git a/src/ui/util.h b/src/ui/util.h
index e198962fa1..8469a628d9 100644
--- a/src/ui/util.h
+++ b/src/ui/util.h
@@ -17,10 +17,13 @@
 #include <exception>
 
 #include <gdkmm/rgba.h>
+#include <gtkmm/cellrenderer.h>
+#include <gtkmm/enums.h>
 #include <gtkmm/stylecontext.h>
 #include <2geom/point.h>
 #include <2geom/rect.h>
 #include <2geom/affine.h>
+#include <gtkmm/widget.h>
 
 /*
  * Use these errors when building from glade files for graceful
@@ -53,12 +56,20 @@ void reveal_widget(Gtk::Widget *widget, bool show);
 // check if widget in a container is actually visible
 bool is_widget_effectively_visible(Gtk::Widget const *widget);
 
-namespace Inkscape {
-namespace UI {
-// Utility function to ensure correct sizing after adding child widgets
+namespace Inkscape::UI {
+
+/// Utility function to ensure correct sizing after adding child widgets.
 void resize_widget_children(Gtk::Widget *widget);
+
+inline void widget_show(Gtk::Widget &widget, bool show)
+{
+    show ? widget.show() : widget.hide();
 }
-}
+
+/// Translate cell renderer state to style flags.
+Gtk::StateFlags cell_flags_to_state_flags(Gtk::CellRendererState state);
+
+} // namespace Inkscape::UI
 
 // Mix two RGBA colors using simple linear interpolation:
 //  0 -> only a, 1 -> only b, x in 0..1 -> (1 - x)*a + x*b
diff --git a/src/ui/widget/shapeicon.cpp b/src/ui/widget/shapeicon.cpp
index 6b7a9d9ff8..fc6844324c 100644
--- a/src/ui/widget/shapeicon.cpp
+++ b/src/ui/widget/shapeicon.cpp
@@ -9,7 +9,10 @@
  */
 
 
+#include <gtkmm/cellrenderer.h>
+#include <gtkmm/enums.h>
 #include "color.h"
+#include "ui/util.h"
 #include "ui/widget/shapeicon.h"
 #include "ui/icon-loader.h"
 
@@ -33,8 +36,19 @@ void CellRendererItemIcon::render_vfunc(const Cairo::RefPtr<Cairo::Context>& cr,
                                       const Gdk::Rectangle& cell_area,
                                       Gtk::CellRendererState flags)
 {
+    property_mode() = Gtk::CELL_RENDERER_MODE_ACTIVATABLE;
+
     std::string shape_type = _property_shape_type.get_value();
-    std::string highlight = SPColor(_property_color.get_value()).toString();
+    std::string highlight;
+    auto color = _property_color.get_value();
+    if (color == 0) {
+        auto style_context = widget.get_style_context();
+        Gdk::RGBA fg = style_context->get_color(cell_flags_to_state_flags(flags));
+        highlight = fg.to_string();
+    }
+    else {
+        highlight = SPColor(color).toString();
+    }
     std::string cache_id = shape_type + "-" + highlight;
 
     // if the icon isn't cached, render it to a pixbuf
@@ -98,6 +112,15 @@ void CellRendererItemIcon::get_preferred_width_vfunc(Gtk::Widget& widget, int& m
     nat_w = _size + 4;
 }   
 
+bool CellRendererItemIcon::activate_vfunc(GdkEvent* event,
+                                Gtk::Widget& widget,
+                                const Glib::ustring& path,
+                                const Gdk::Rectangle& background_area,
+                                const Gdk::Rectangle& cell_area,
+                                Gtk::CellRendererState flags) {
+    _signal_activated.emit(path);
+    return true;
+}
 
 } // namespace Widget
 } // namespace UI
diff --git a/src/ui/widget/shapeicon.h b/src/ui/widget/shapeicon.h
index b5ca0337a5..8e09e64fe8 100644
--- a/src/ui/widget/shapeicon.h
+++ b/src/ui/widget/shapeicon.h
@@ -55,6 +55,11 @@ public:
         return _property_clipmask.get_proxy();
     }
   
+    typedef sigc::signal<void (Glib::ustring)> type_signal_activated;
+    type_signal_activated signal_activated() {
+        return _signal_activated;
+    }
+
 protected:
     void render_vfunc(const Cairo::RefPtr<Cairo::Context>& cr, 
                       Gtk::Widget& widget,
@@ -69,8 +74,14 @@ protected:
     void get_preferred_width_vfunc(Gtk::Widget& widget, int& min_w, int& nat_w) const override;
     void get_preferred_height_vfunc(Gtk::Widget& widget, int& min_h, int& nat_h) const override;
 
+    bool activate_vfunc(GdkEvent* event,
+                        Gtk::Widget& widget,
+                        const Glib::ustring& path,
+                        const Gdk::Rectangle& background_area,
+                        const Gdk::Rectangle& cell_area,
+                        Gtk::CellRendererState flags) override;
 private:
-  
+    type_signal_activated _signal_activated;
     int _size;
     Glib::Property<std::string> _property_shape_type;
     Glib::Property<unsigned int> _property_color;
diff --git a/src/widgets/sp-xmlview-tree.cpp b/src/widgets/sp-xmlview-tree.cpp
index a650b317f8..133639f9e4 100644
--- a/src/widgets/sp-xmlview-tree.cpp
+++ b/src/widgets/sp-xmlview-tree.cpp
@@ -13,10 +13,16 @@
 #include "sp-xmlview-tree.h"
 
 #include <cstring>
+#include <glibmm/markup.h>
+#include <glibmm/property.h>
+#include <glibmm/ustring.h>
 #include <gmodule.h>
+#include <gtkmm/cellrenderer.h>
+#include <gtkmm/cellrenderertext.h>
 #include <memory>
 #include <string>
 
+#include "ui/syntax.h"
 #include "xml/node-observer.h"
 #include "xml/node.h"
 
@@ -40,7 +46,7 @@ Inkscape::XML::Node *dragging_repr = nullptr;
 
 } // namespace
 
-enum { STORE_TEXT_COL = 0, STORE_DATA_COL, STORE_N_COLS };
+enum { STORE_TEXT_COL = 0, STORE_DATA_COL, STORE_MARKUP_COL, STORE_N_COLS };
 
 static void sp_xmlview_tree_destroy(GtkWidget * object);
 
@@ -67,6 +73,11 @@ static void sp_remove_newlines_and_tabs(std::string &val, size_t const maxlen =
 
 namespace {
 
+static auto null_to_empty(char const *str)
+{
+    return str ? str : "";
+}
+
 class ElementNodeObserver final : public Inkscape::XML::NodeObserver
 {
     NodeData *_nodedata;
@@ -166,35 +177,37 @@ public:
             return;
         }
 
-        gchar const* node_name = repr->name();
-        gchar const* id_value = repr->attribute("id");
-        gchar const* label_value = repr->attribute("inkscape:label");
-        gchar* display_text;
-
-        if (id_value && label_value) {
-            display_text = g_strdup_printf ("<%s id=\"%s\" inkscape:label=\"%s\">", node_name, id_value, label_value);
-        } else if (id_value) {
-            display_text = g_strdup_printf ("<%s id=\"%s\">", node_name, id_value);
-        } else if (label_value) {
-            display_text = g_strdup_printf ("<%s inkscape:label=\"%s\">", node_name, label_value);
-        } else {
-            display_text = g_strdup_printf ("<%s>", node_name);
+        auto node_name = Glib::ustring(null_to_empty(repr->name()));
+        auto pos = node_name.find("svg:");
+        if (pos != Glib::ustring::npos) {
+            // Do not decorate element names the with default namespace "svg"; it is just visual noise.
+            node_name.erase(pos, 4);
         }
 
-        GtkTreeIter iter;
-        if (tree_ref_to_iter(_nodedata->tree, &iter,  _nodedata->rowref)) {
-            gtk_tree_store_set (GTK_TREE_STORE(_nodedata->tree->store), &iter, STORE_TEXT_COL, display_text, -1);
+        // Build a plain-text and a markup-enabled representation of the node.
+        auto &formatter = *_nodedata->tree->formatter;
+        auto display_text = Glib::ustring::compose("<%1", node_name);
+        formatter.openTag(node_name.c_str());
+
+        if (auto id_value = repr->attribute("id")) {
+            display_text += Glib::ustring::compose(" id=\"%1\"", id_value);
+            formatter.addAttribute("id", id_value);
         }
+        if (auto label_value = repr->attribute("inkscape:label")) {
+            display_text += Glib::ustring::compose(" inkscape:label=\"%1\"", label_value);
+            formatter.addAttribute("inkscape:label", label_value);
+        }
+        display_text += ">";
+        auto markup = formatter.finishTag();
 
-        g_free(display_text);
+        GtkTreeIter iter;
+        if (tree_ref_to_iter(_nodedata->tree, &iter, _nodedata->rowref)) {
+            gtk_tree_store_set(GTK_TREE_STORE(_nodedata->tree->store), &iter, STORE_TEXT_COL, display_text.c_str(), -1);
+            gtk_tree_store_set(GTK_TREE_STORE(_nodedata->tree->store), &iter, STORE_MARKUP_COL, markup.c_str(), -1);
+        }
     }
 };
 
-static auto null_to_empty(char const *str)
-{
-    return str ? str : "";
-}
-
 class TextNodeObserver final : public Inkscape::XML::NodeObserver
 {
     NodeData *_nodedata;
@@ -210,13 +223,16 @@ public:
         if (_nodedata->tree->blocked)
             return;
 
-        auto nolinecontent = std::string("\"").append(null_to_empty(new_content.pointer())).append("\"");
-        sp_remove_newlines_and_tabs(nolinecontent);
+        auto text_content = std::string("\"").append(null_to_empty(new_content.pointer())).append("\"");
+        sp_remove_newlines_and_tabs(text_content);
+
+        auto &formatter = *_nodedata->tree->formatter;
+        auto markup = formatter.formatContent(text_content.c_str(), false);
 
         GtkTreeIter iter;
         if (tree_ref_to_iter(_nodedata->tree, &iter, _nodedata->rowref)) {
-            gtk_tree_store_set(GTK_TREE_STORE(_nodedata->tree->store), &iter, STORE_TEXT_COL, nolinecontent.c_str(),
-                               -1);
+            gtk_tree_store_set(GTK_TREE_STORE(_nodedata->tree->store), &iter, STORE_TEXT_COL, text_content.c_str(), -1);
+            gtk_tree_store_set(GTK_TREE_STORE(_nodedata->tree->store), &iter, STORE_MARKUP_COL, markup.c_str(), -1);
         }
     }
 };
@@ -235,13 +251,16 @@ public:
         if (_nodedata->tree->blocked)
             return;
 
-        auto nolinecontent = std::string("<!--").append(null_to_empty(new_content.pointer())).append("-->");
-        sp_remove_newlines_and_tabs(nolinecontent);
+        auto comment = std::string("<!--").append(null_to_empty(new_content.pointer())).append("-->");
+        sp_remove_newlines_and_tabs(comment);
+
+        auto &formatter = *_nodedata->tree->formatter;
+        auto markup = formatter.formatComment(comment.c_str(), false);
 
         GtkTreeIter iter;
         if (tree_ref_to_iter(_nodedata->tree, &iter, _nodedata->rowref)) {
-            gtk_tree_store_set(GTK_TREE_STORE(_nodedata->tree->store), &iter, STORE_TEXT_COL, nolinecontent.c_str(),
-                               -1);
+            gtk_tree_store_set(GTK_TREE_STORE(_nodedata->tree->store), &iter, STORE_TEXT_COL, comment.c_str(), -1);
+            gtk_tree_store_set(GTK_TREE_STORE(_nodedata->tree->store), &iter, STORE_MARKUP_COL, markup.c_str(), -1);
         }
     }
 };
@@ -260,13 +279,16 @@ public:
         if (_nodedata->tree->blocked)
             return;
 
-        auto nolinecontent = std::string("<?").append(repr.name()).append(" ").append(null_to_empty(new_content.pointer())).append("?>");
-        sp_remove_newlines_and_tabs(nolinecontent);
+        auto processing_instr = std::string("<?").append(repr.name()).append(" ").append(null_to_empty(new_content.pointer())).append("?>");
+        sp_remove_newlines_and_tabs(processing_instr);
+
+        auto &formatter = *_nodedata->tree->formatter;
+        auto markup = formatter.formatProlog(processing_instr.c_str());
 
         GtkTreeIter iter;
         if (tree_ref_to_iter(_nodedata->tree, &iter, _nodedata->rowref)) {
-            gtk_tree_store_set(GTK_TREE_STORE(_nodedata->tree->store), &iter, STORE_TEXT_COL, nolinecontent.c_str(),
-                               -1);
+            gtk_tree_store_set(GTK_TREE_STORE(_nodedata->tree->store), &iter, STORE_TEXT_COL, processing_instr.c_str(), -1);
+            gtk_tree_store_set(GTK_TREE_STORE(_nodedata->tree->store), &iter, STORE_MARKUP_COL, markup.c_str(), -1);
         }
     }
 };
@@ -328,6 +350,33 @@ static gboolean on_test_expand_row( //
     return false;
 }
 
+/** Node name renderer for XML tree.
+ *  It knows to use markup, but falls back to plain text for selected nodes.
+ */
+class NodeRenderer : public Gtk::CellRendererText {
+public:
+    NodeRenderer():
+        Glib::ObjectBase(typeid(CellRendererText)),
+        Gtk::CellRendererText(),
+        _property_plain_text(*this, "plain", "-") {}
+
+    // "text" and "markup" properties from CellRendererText are in use for marked up text;
+    // we need a separate property for plain text (placeholder_text could be hijacked potentially)
+    Glib::Property<Glib::ustring> _property_plain_text;
+
+    void render_vfunc(const Cairo::RefPtr<Cairo::Context>& ctx,
+                      Gtk::Widget& widget,
+                      const Gdk::Rectangle& background_area,
+                      const Gdk::Rectangle& cell_area,
+                      Gtk::CellRendererState flags) override {
+        if (flags & Gtk::CELL_RENDERER_SELECTED) {
+            // use plain text instead of marked up text to render selected nodes, so they are legible
+            property_text() = _property_plain_text.get_value();
+        }
+        Gtk::CellRendererText::render_vfunc(ctx, widget, background_area, cell_area, flags);
+    }
+};
+
 GtkWidget *sp_xmlview_tree_new(Inkscape::XML::Node * repr, void * /*factory*/, void * /*data*/)
 {
     SPXMLViewTree *tree = SP_XMLVIEW_TREE(g_object_new (SP_TYPE_XMLVIEW_TREE, nullptr));
@@ -337,8 +386,14 @@ GtkWidget *sp_xmlview_tree_new(Inkscape::XML::Node * repr, void * /*factory*/, v
     gtk_tree_view_set_enable_search (GTK_TREE_VIEW(tree), TRUE);
     gtk_tree_view_set_search_equal_func (GTK_TREE_VIEW(tree), search_equal_func, nullptr, nullptr);
 
-    GtkCellRenderer *renderer = gtk_cell_renderer_text_new ();
-    GtkTreeViewColumn *column = gtk_tree_view_column_new_with_attributes ("", renderer, "text", STORE_TEXT_COL, nullptr);
+    auto r = new NodeRenderer();
+    tree->renderer = r;
+
+    GtkCellRenderer* renderer = r->Gtk::CellRenderer::gobj();
+    GtkTreeViewColumn *column = gtk_tree_view_column_new_with_attributes("", renderer,
+        "markup", STORE_MARKUP_COL, // marked up text for decorated color output
+        "plain", STORE_TEXT_COL,    // plain text for searching and rendering selected nodes
+        nullptr);
     gtk_tree_view_append_column (GTK_TREE_VIEW (tree), column);
     gtk_cell_renderer_set_padding (renderer, 2, 0);
     gtk_tree_view_column_set_sizing (column, GTK_TREE_VIEW_COLUMN_AUTOSIZE);
@@ -350,6 +405,8 @@ GtkWidget *sp_xmlview_tree_new(Inkscape::XML::Node * repr, void * /*factory*/, v
     g_signal_connect(GTK_TREE_VIEW(tree), "drag-motion",  G_CALLBACK(do_drag_motion), tree);
     g_signal_connect(GTK_TREE_VIEW(tree), "test-expand-row", G_CALLBACK(on_test_expand_row), nullptr);
 
+    tree->formatter = new Inkscape::UI::Syntax::XMLFormatter();
+
     return GTK_WIDGET(tree);
 }
 
@@ -359,7 +416,7 @@ void sp_xmlview_tree_class_init(SPXMLViewTreeClass * klass)
 {
     auto widget_class = GTK_WIDGET_CLASS(klass);
     widget_class->destroy = sp_xmlview_tree_destroy;
-    
+
     // Signal for when a tree drag and drop has completed
     g_signal_new (  "tree_move",
         G_TYPE_FROM_CLASS(klass),
@@ -382,6 +439,11 @@ void sp_xmlview_tree_destroy(GtkWidget * object)
 {
 	SPXMLViewTree * tree = SP_XMLVIEW_TREE (object);
 
+    delete tree->renderer;
+    tree->renderer = nullptr;
+    delete tree->formatter;
+    tree->formatter = nullptr;
+
 	sp_xmlview_tree_set_repr (tree, nullptr);
 
 	GTK_WIDGET_CLASS(sp_xmlview_tree_parent_class)->destroy (object);
@@ -788,7 +850,7 @@ sp_xmlview_tree_set_repr (SPXMLViewTree * tree, Inkscape::XML::Node * repr)
     }
     tree->repr = repr;
     if (repr) {
-        tree->store = gtk_tree_store_new(STORE_N_COLS, G_TYPE_STRING, G_TYPE_POINTER);
+        tree->store = gtk_tree_store_new(STORE_N_COLS, G_TYPE_STRING, G_TYPE_POINTER, G_TYPE_STRING);
 
         Inkscape::GC::anchor(repr);
         add_node(tree, nullptr, nullptr, repr);
diff --git a/src/widgets/sp-xmlview-tree.h b/src/widgets/sp-xmlview-tree.h
index 36ea43f1c5..ca9b3e005a 100644
--- a/src/widgets/sp-xmlview-tree.h
+++ b/src/widgets/sp-xmlview-tree.h
@@ -13,6 +13,7 @@
 
 #include <gtk/gtk.h>
 #include <glib.h>
+#include <gtkmm/cellrenderertext.h>
 
 namespace Inkscape::XML {
 class Node;
@@ -29,13 +30,16 @@ class Node;
 
 struct SPXMLViewTree;
 struct SPXMLViewTreeClass;
+namespace Inkscape::UI::Syntax { class XMLFormatter; }
 
 struct SPXMLViewTree
 {
-	GtkTreeView tree;
-	GtkTreeStore *store;
-	Inkscape::XML::Node * repr;
-	gint blocked;
+    GtkTreeView tree;
+    GtkTreeStore *store;
+    Inkscape::XML::Node * repr;
+    gint blocked;
+    Gtk::CellRendererText* renderer;
+    Inkscape::UI::Syntax::XMLFormatter* formatter;
 };
 
 struct SPXMLViewTreeClass
-- 
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