Bug Report Preview window doesn't fit frame if using fractional Qt window scaling (env QT_SCREEN_SCALE_FACTORS)

[Zorael]

Manjaro/Arch x86_64, obs-studio 21.1.2-3 from community repo. kwin 5.13.4, window scaling set to 1.5x. The machine is a Dell XPS 13 with a 3200x1800 display.

The preview window doesn't scale to its frame, and old garbage content gets painted in the empty space. Resizing the window makes for a very messy result. Attaching a screenshot.

edit: It behaves properly if I unset the QT_SCREEN_SCALE_FACTORS variable, or via it set the scaling to a non-fractional number (eg 2 instead of 1.5).

$ QT_SCREEN_SCALE_FACTORS= obs  # works
$ QT_SCREEN_SCALE_FACTORS=2 obs  # works
$ QT_SCREEN_SCALE_FACTORS="eDP1=2;DP1=2;DP2=2;HDMI1=2;HDMI2=2;VIRTUAL1=2;" obs  # works
$ QT_SCREEN_SCALE_FACTORS="eDP1=1.5;DP1=1.5;DP2=1.5;HDMI1=1.5;HDMI2=1.5;VIRTUAL1=1.5;" obs  # garbage

 

[Zorael]

Log file with GL errors: https://hastebin.com/ovaqicadek