gtk4: Improve handling of RGBA GL textures in GTK

GTK 4.14 comes with a new GL renderer that does not support GL shader nodes anymore, so the conversion from non-premultiplied alpha to premultiplied alpha has to happen differently.

For GTK 4.14 or newer we use the correct format directly when building the texture, but only if a GLES3+ context is used. In that case the NGL renderer is used by GTK, which supports non-premultiplied formats correctly and fast.

For GTK 4.10-4.12, or 4.14 and newer if a GLES2 context is used, we use a self-mask to pre-multiply the alpha.

For GTK before 4.10, we use a GL shader and hope that it works.

Fixes #488 (closed)

mentioned in issue #488 (closed)

added 3 commits

• d2d2fd85 - gtk4: Improve handling of RGBA GL textures in GTK
• a5e6a1ad - gtk4: Always draw a black background behind the video frame
• 67e1ccb4 - gtk4: Add property to the paintable for selecting the background color

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resolved all threads

assigned to @gstreamer-merge-bot

mentioned in commit slomo/gst-plugins-rs@98a27112

mentioned in commit slomo/gst-plugins-rs@1f3a7bf1

mentioned in commit slomo/gst-plugins-rs@c20a8a08

added 3 commits

• c20a8a08 - gtk4: Improve handling of RGBA GL textures in GTK
• 1f3a7bf1 - gtk4: Always draw a black background behind the video frame
• 98a27112 - gtk4: Add property to the paintable for selecting the background color

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assigned to @slomo and unassigned @gstreamer-merge-bot

I couldn't merge this branch: CI failed! See pipeline https://gitlab.freedesktop.org/slomo/gst-plugins-rs/-/pipelines/1097536.

added 14 commits

• 98a27112...09e9c047 - 10 commits from branch gstreamer:main
• 4183bc6f - gtk4: Improve handling of RGBA GL textures in GTK
• acd642a7 - gtk4: Always draw a black background behind the video frame
• 150925b9 - gtk4: Add property to the paintable for selecting the background color
• e266bbcf - ci: Ignore GTK4 plugin when building with `--all-features`

Compare with previous version

resolved all threads

assigned to @gstreamer-merge-bot and unassigned @slomo

mentioned in commit slomo/gst-plugins-rs@80355011

added 4 commits

• 80355011 - gtk4: Improve handling of RGBA GL textures in GTK
• 9971f71e - gtk4: Always draw a black background behind the video frame
• 0fe4e0bf - gtk4: Add property to the paintable for selecting the background color
• 76b9836e - ci: Ignore GTK4 plugin when building with `--all-features`

Compare with previous version

mentioned in commit slomo/gst-plugins-rs@76b9836e

mentioned in commit slomo/gst-plugins-rs@9971f71e

mentioned in commit slomo/gst-plugins-rs@0fe4e0bf

assigned to @slomo and unassigned @gstreamer-merge-bot