Comment 29 for bug 1751593

Created attachment 368368
Debug patch to exhibit the issue

This patch does:

 - Set the gdk_window frame gb_color to yellow
 - Set the metawindow actor color to red
 - Removes the repaint to black in meta_frames_draw()

The idea is to show the yellow/red blinking.

To reproduce

 1. Build mutter with this patch
 2. Run mutter nested:
    $ jhbuild run mutter --wayland --nested
 3. Run gtk3-demo “Application Class” with x11 backend under Wayland:
    $ DISPLAY=:1 GDK_BACKEND=x11 gtk3-demo --run application_demo
 4. Resize the “Application Class” window (that one uses server-side decorations, so decorated by mutter)

Now what does this show:

 1. The initial color (yellow with this patch) comes from the gdk_window.
 2. meta_frames_draw() clears the window to black, that doesn't help!
 3. Using an alpha of 0.0 for the GDK window background makes the color black again, as if the mutter's own gdk_window used for the frame wasn't composited...