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glium 0.34.0

Elegant and safe OpenGL wrapper. Glium is an intermediate layer between OpenGL and your application. You still need to manually handle the graphics pipeline, but without having to use OpenGL's old and error-prone API. Its objectives: - Be safe to use. Many aspects of OpenGL that can trigger a crash if misused are automatically handled by glium. - Provide an API that enforces good pratices such as RAII or stateless function calls. - Be compatible with all OpenGL versions that support shaders, providing unified API when things diverge. - Avoid all OpenGL errors beforehand. - Produce optimized OpenGL function calls, and allow the user to easily use modern OpenGL techniques.
Documentation 
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use crate::BlitTarget;
use crate::Rect;

use crate::context::Context;
use crate::ContextExt;

use crate::fbo::FramebuffersContainer;
use crate::fbo::ValidatedAttachments;

use crate::gl;
use crate::version::Version;
use crate::version::Api;

pub fn blit(context: &Context, source: Option<&ValidatedAttachments<'_>>,
            target: Option<&ValidatedAttachments<'_>>, mask: gl::types::GLbitfield,
            src_rect: &Rect, target_rect: &BlitTarget, filter: gl::types::GLenum)
{
    assert!(
        (mask & gl::DEPTH_BUFFER_BIT == 0 && mask & gl::STENCIL_BUFFER_BIT == 0) || filter == gl::NEAREST,
        "Blitting the depth and/or stencil buffer with filter being anything other than GL_NEAREST is an invalid operation."
    );
    unsafe {
        let mut ctxt = context.make_current();

        // FIXME: we don't draw on it
        let source = FramebuffersContainer::get_framebuffer_for_drawing(&mut ctxt, source);
        let target = FramebuffersContainer::get_framebuffer_for_drawing(&mut ctxt, target);

        // scissor testing influences blitting
        if ctxt.state.enabled_scissor_test {
            ctxt.gl.Disable(gl::SCISSOR_TEST);
            ctxt.state.enabled_scissor_test = false;
        }

        // trying to do a named blit if possible
        if ctxt.version >= &Version(Api::Gl, 4, 5) {
            ctxt.gl.BlitNamedFramebuffer(source, target,
                src_rect.left as gl::types::GLint,
                src_rect.bottom as gl::types::GLint,
                (src_rect.left + src_rect.width) as gl::types::GLint,
                (src_rect.bottom + src_rect.height) as gl::types::GLint,
                target_rect.left as gl::types::GLint, target_rect.bottom as gl::types::GLint,
                (target_rect.left as i32 + target_rect.width) as gl::types::GLint,
                (target_rect.bottom as i32 + target_rect.height) as gl::types::GLint, mask, filter);

            return;
        }

        // binding source framebuffer
        if ctxt.state.read_framebuffer != source {
            if ctxt.version >= &Version(Api::Gl, 3, 0) {
                ctxt.gl.BindFramebuffer(gl::READ_FRAMEBUFFER, source);
                ctxt.state.read_framebuffer = source;

            } else {
                ctxt.gl.BindFramebufferEXT(gl::READ_FRAMEBUFFER_EXT, source);
                ctxt.state.read_framebuffer = source;
            }
        }

        // binding target framebuffer
        if ctxt.state.draw_framebuffer != target {
            if ctxt.version >= &Version(Api::Gl, 3, 0) {
                ctxt.gl.BindFramebuffer(gl::DRAW_FRAMEBUFFER, target);
                ctxt.state.draw_framebuffer = target;

            } else {
                ctxt.gl.BindFramebufferEXT(gl::DRAW_FRAMEBUFFER_EXT, target);
                ctxt.state.draw_framebuffer = target;
            }
        }

        // doing the blit
        if ctxt.version >= &Version(Api::Gl, 3, 0) {
            ctxt.gl.BlitFramebuffer(src_rect.left as gl::types::GLint,
                src_rect.bottom as gl::types::GLint,
                (src_rect.left + src_rect.width) as gl::types::GLint,
                (src_rect.bottom + src_rect.height) as gl::types::GLint,
                target_rect.left as gl::types::GLint, target_rect.bottom as gl::types::GLint,
                (target_rect.left as i32 + target_rect.width) as gl::types::GLint,
                (target_rect.bottom as i32 + target_rect.height) as gl::types::GLint, mask, filter);

        } else {
            ctxt.gl.BlitFramebufferEXT(src_rect.left as gl::types::GLint,
                src_rect.bottom as gl::types::GLint,
                (src_rect.left + src_rect.width) as gl::types::GLint,
                (src_rect.bottom + src_rect.height) as gl::types::GLint,
                target_rect.left as gl::types::GLint, target_rect.bottom as gl::types::GLint,
                (target_rect.left as i32 + target_rect.width) as gl::types::GLint,
                (target_rect.bottom as i32 + target_rect.height) as gl::types::GLint, mask, filter);
        }
    }
}