Possible fix for notification shadows with X11

Submitted by Nikita Zlobin

Assigned to Simon Steinbeiß @ochosi

Link to original bug (#16800)

Description

I noticed, that XShape, despite being primitive alpha channel replacement, really affects default shadows, produced by compton. However, in gentoo xfce4-notifyd doesn't even depend on any x11 stuff, so I'm not sure is special x11 support would be ok. I just completed PR for Dunst, which already used xshape, being not rgba-enabled, but it directly uses x11/cairo combo without toolkits like gtk. I noticed at least some mentions or X11 (among flags/libs in build system files like Makefile.am). It would be some chance to have good shadows with rounded notifications in x11 (no idea, what is in wayland, since never tried it).

Version: git