From cedd07a05e3ec50d266e9ad09aff996dd496933e Mon Sep 17 00:00:00 2001
From: Martin Owens <doctormo@gmail.com>
Date: Mon, 8 Jan 2024 20:07:49 -0500
Subject: [PATCH] Feature: Group Translucency

When entering a group that is not a layer, we turn the opacity down for all
objects outside of that group to make it clear that we are inside a group
and which one and which objects we're working with.
---
 src/desktop.cpp | 16 ++++++++++++++++
 src/desktop.h   |  3 +++
 2 files changed, 19 insertions(+)

diff --git a/src/desktop.cpp b/src/desktop.cpp
index 7abd51c830..846202fb2d 100644
--- a/src/desktop.cpp
+++ b/src/desktop.cpp
@@ -182,6 +182,11 @@ void SPDesktop::_setupCanvasItems()
     _canvas_drawing->connect_drawing_event(sigc::mem_fun(*this, &SPDesktop::drawing_handler));
 
     canvas->set_drawing(_canvas_drawing->get_drawing());
+
+    _layer_changed_connection = _layer_manager->connectCurrentLayerChanged([this](SPGroup *group) {
+        updateTranslucenyGroups();
+    });
+
 }
 
 SPDesktop::~SPDesktop()
@@ -1395,6 +1400,17 @@ void SPDesktop::on_zoom_end(Gdk::EventSequence * /*sequence*/)
     _begin_zoom.reset();
 }
 
+/**
+ * Set or unset the translucency group if needed.
+ */
+void SPDesktop::updateTranslucenyGroups()
+{
+    auto group = _layer_manager->currentLayer();
+    bool enabled = !group->isLayer();
+    // TODO: Add preference to control this here?
+    _translucency_group->setSolidItem(enabled ? group : nullptr);
+}
+
 /*
   Local Variables:
   mode:c++
diff --git a/src/desktop.h b/src/desktop.h
index 63c4c01064..39a66eaa14 100644
--- a/src/desktop.h
+++ b/src/desktop.h
@@ -550,6 +550,7 @@ private:
     sigc::scoped_connection _reconstruction_finish_connection;
     sigc::scoped_connection _schedule_zoom_from_document_connection;
     sigc::scoped_connection _y_axis_flipped;
+    sigc::scoped_connection _layer_changed_connection;
 
     bool drawing_handler(Inkscape::CanvasEvent const &event, Inkscape::DrawingItem *item);
     void reconstruction_start();
@@ -563,6 +564,8 @@ private:
     void on_zoom_end(Gdk::EventSequence *sequence);
 
     void onStatusMessage(Inkscape::MessageType type, char const *message);
+
+    void updateTranslucenyGroups();
 };
 
 #endif // INKSCAPE_DESKTOP_H
-- 
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