Bug 272364 – REGRESSION(??????@main): [GTK] Regression with webview background color rendering and DRI

• Component: WebKitGTK
• Status: NEW

[Philip Chimento]

Created attachment 470827 [details]
Sample program

The attached sample program demonstrates a web view in GTK 3 that is supposed to be transparent, i.e. renders the HTML on top of the background color of the GtkWindow that the web view is placed in.

At some point between GNOME 43 (webkit2gtk-4.1 2.40.5) and 44 (webkit2gtk-4.1 2.42.5) there was a regression that caused this to stop working. Instead of the background color of the window, the contents of the screen behind the window show through, but in a glitchy way. However, if the DRI permission is disabled, the glitch is gone, and the behaviour is as expected.

See the attached video where I executed the sample program in subsequent flatpak runtimes:

- org.gnome.Platform//43 with --device=dri - works as expected
- org.gnome.Platform//44 with --device=dri - glitches
- org.gnome.Platform//44 without --device=dri - works as expected

The equivalent program using GTK 4 and webkitgtk-6.0 doesn't seem to exhibit this problem.

[Philip Chimento]

Created attachment 470828 [details]
Video showing glitchy behaviour

[Michael Catanzaro]

I can reproduce. I built 260527@main (2.40 branchpoint) with intention of bisecting this, but the bug occurs there exactly the same for me. My assumption is that something else in the GNOME runtime changed between 43 and 44. Unfortunately it's much harder to guess what it could be since we took so long to notice this regression.