Comment 4 for bug 1845102

@vanvugt You're right, it's not the theme. I spent some time investigating this:

The tearing occurs while using GNOME-MPV or Celluloid. It's Z-shaped, and constant. It occurs after a slight flicker 5-10 seconds into playing any video. (And doesn't appear in screen captured videos, it sounds like a graphics glitch).

If I use GNOME-MPV and disable client side decorations, or use VLC or any other media player (besides Chromium), there's a noticeable flicker-stutter if I change the volume (when the OSD pops up and disappears). During this time, the desktop icons appear for a fraction of a second, then disappear.

This problem doesn't occur in Arch/vanilla GNOME, but it does occur in 19.04 if I turn on the Adwaita theme (both the Z-shaped tearing and the flicker OSD problem).

I figure that the old Yaru theme was masking this mutter issue somehow. There's probably an extension or some config file causing the desktop to show up for a fraction of a second then disappear.

Turning off all of the extensions (desktop icons, dash to dock etc.) doesn't help the situation.
Removing them from /usr/share/gnome-shell doesn't work either.
I've tested this on three separate computers, they all show the glitch (one was 19.04 with Adwaita enabled, the other two were 19.10 without any tweaking enabled).

This doesn't occur on Wayland though, could it be an xorg configuration issue?
I'm really sorry I'm harping on this so much but I prefer X because I can play video games there :D