Bug 484939

Summary: hearts of iron 4 output not scaling correctly
Product: [Plasma] kwin Reporter: Harald Sitter <sitter>
Component: wayland-genericAssignee: KWin default assignee <kwin-bugs-null>
Status: RESOLVED UPSTREAM    
Severity: normal CC: xaver.hugl
Priority: NOR    
Version First Reported In: git master   
Target Milestone: ---   
Platform: Other   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: drm_info output while windows is fullscreen

Description Harald Sitter 2024-04-02 18:20:16 UTC 
SUMMARY
When the game hearts of iron 4 is configured to a lower resolution than that of the desktop the remaining screen is filled with artifacts instead of scaled correctly

STEPS TO REPRODUCE
1. get hoi4 on steam & install & start
2. go to options
3. change resolution to one lower than the desktop (in my case from 2160 to 1080). display mode is fullscreen FWIW. 
4. restart game

OBSERVED RESULT
output broken, mouse input is also not matching up with the actual correctly painted part of the screen

EXPECTED RESULT
output should be 1080

SOFTWARE/OS VERSIONS
KDE Plasma Version: 6.0.80
KDE Frameworks Version: 6.1.0
Qt Version: 6.6.3
Kernel Version: 6.8.2-arch2-1 (64-bit)
Graphics Platform: Wayland
Processors: 12 × AMD Ryzen 5 3600X 6-Core Processor
Memory: 31.2 GiB of RAM
Graphics Processor: AMD Radeon RX 5700 XT

ADDITIONAL INFORMATION
Parts of the screen seem to redraw somewhat consistently on alt-tabbing revealing that the top left corner is where input gets received but the bottom left corner is the one that gets painted to.

I have a three display setup but the two side screens are currently disabled via the kscreen kcm.
Comment 1 Harald Sitter 2024-04-02 18:21:56 UTC 
screenshot https://imgur.com/a/fzwJeTI
Comment 2 Harald Sitter 2024-04-02 18:22:22 UTC 
Created attachment 168066 [details]
drm_info output while windows is fullscreen
Comment 3 Zamundaaa 2024-04-02 18:56:18 UTC 
The game seems to get direct scanout, judging by the XRGB8888 format. Given that, this looks quite wrong:
    │       ├───"SRC_W" (atomic): range [0, UINT32_MAX] = 3840
    │       ├───"SRC_H" (atomic): range [0, UINT32_MAX] = 2160
Comment 4 Zamundaaa 2024-04-02 19:31:56 UTC 
I managed to reproduce this in Half Life 2 and KWin seems to do everything correctly; we get a full resolution buffer from Xwayland... and it's very similar to https://gitlab.freedesktop.org/xorg/xserver/-/issues/1595, so I'm pretty confident it's that Xwayland bug