firefox on xwayland unusable after gnome autostart

[Birgit Edel]

Early starts of firefox on gnome on wayland on Ubuntu 20.04.4 are unusable. Early meaning directly after session start from gdm.

If I put firefox.desktop into ~/.config/autostart/, firefox will start as expected, successfully load my homepage (as evidenced in server logs), but fail to display windows decoration or contents or react on input. The space occupied by the window will be either black, matching last shown pixels in the place (background, other windows) or alternate between such with varying flicker frequency.

For avoidance of ambiguity, the mode affected by the bug is windowProtocol=xwayland (as in about:support)

The bug can be worked around, either method is sufficient on its own:
a) forcing windowProtocol=wayland through environment MOZ_ENABLE_WAYLAND=1
b) starting firefox later, through a prepended sleep 10 call

Mostly for documenting the workarounds, I understand that this might not be worth fixing as firefox snap approaches similar quality, see also #1970884