[DRM backend] Mouse look broken in Wolfenstein II: The New Colossus

[tobiasjakobi]

Affected game: Wolfenstein II: The New Colossus Affected version: 3.15.5 (went back to 3.14.24 which has the same problem)

Mouse behaviour:

• mouse is stuck in the upper-left area in menu, haven't managed to get it un-stuck at all
• mouse uncontrollable in-game, i.e. even tiny movements of the mouse device let's the view jump all over the place

Gamescope setup:

• DRM backend
• started by greetd
• gamescope spawns Steam session

Emulation layer:

• GE-Proton9-13

Working setup:

• Sway v1.9 (i.e. the issue does not appear if you take gamescope out of the equation)
• wlroots v0.17.4

Might be related to these:

• https://github.com/ValveSoftware/gamescope/issues/1559
• https://github.com/ValveSoftware/gamescope/issues/1531

Major differences:

• RE8 and Plague Tale both appear to wrongly restrict mouse input in-game, resulting in too slow or no mouse input at all
• Wolfenstein on the other hand seems to suffer from some scaling issues, i.e. the incoming mouse input is scaled with a an incorrect value
• RE8 and Plague Tale have more or less working cursor input in the menu, whereas Wolfenstein's menu input is totally broken

[tobiasjakobi]

I managed to get the mouse working by applying a similar workaround as in: https://github.com/ValveSoftware/gamescope/issues/1521#issuecomment-2387264197

Here's the changes I use (in top of 3.15.5): https://github.com/tobiasjakobi/gamescope/commit/01b9e6b2d0248376873d367c308ba21a48ca186e

I have no idea however why this works when running the game on Sway. Does Sway already do this integer coordinate buffering?