Touch controls don't work under Steam Deck game mode

[denilsonsa]

How to reproduce:

1. Get a Steam Deck (that's the expensive part).
2. Switch to Desktop Mode (which is just KDE/Plasma).
3. Use Discover to install PySolFC from Flathub.
4. Launch PySolFC. Observe how everything works fine in Desktop Mode. Both the mouse input (emulated via the trackpad) and the touch screen input can be used to play the game and interact with the menus.
5. Add PySolFC as a non-steam game to Steam.
6. Return to Game Mode.
7. Go to your Library (under the Game Mode), then find PySolFC from your non-steam games section.
8. Configure the controller input to emulate a web browser. That's the one that maps mouse to the right trackpad.
9. Launch PySolFC under the Game Mode on Steam Deck.
10. BUG!
    • The mouse input works fine.
    • The touch screen input doesn't work at all.

I don't know what makes PySolFC special (maybe the TK library?), because other tools or games like Warble, LBreakoutHD, Google Chrome, VLC (all installed from Flathub) work fine under the Game Mode (although the pop-up menus can get buggy, but that's a different issue) and they all can be controlled with both (emulated) mouse and the touch screen. But somehow PySolFC doesn't accept touch controls.

Steam OS Game Mode uses gamescope as the compositor; while the desktop mode uses the standard KDE/KWin/Plasma environment. I don't know if they use X11 or Wayland or both.

It might be possible to reproduce this bug using gamescope under other Linux distros, but you probably need a touch screen anyway. Or possibly by running some version of Steam OS under a virtual machine with emulated touch screen. I don't know, I haven't tried those options.