Direct scanout is not used when the monitor is set to scale 200%
Direct scanout is not used when the monitor is set to scale 200%. But it is used (same app window) if I change the scale to 100%.
This is easiest to test with a second monitor connected. Because it has no panel, maximizing a window on it should enable direct scanout. But that only works when the monitor scale is 100%. I am not using fractional scaling.
Tested on mutter main 702f52a0 and gnome-shell main gnome-shell@1cc5e770.