Steam client is swallowing all key and mouse button presses

[spillner]

Running Steam beta branch build 1707518866 on 64-bit Slackware, under X.org 21.1.11 and KDE 5.27.10, with an AMD RX 6600 using the in-kernel amdgpu driver in Linux 6.6.8.

I've had several instances, usually when starting or immediately after exiting a Proton application, where I can still move the mouse cursor but cannot interact with any UI elements, either in the game window, Steam client, or other non-Steam windows. The system is not frozen and I can see the contents of other windows updating, but most button and keypresses, including alt-Tab, seem to be ignored. When this happens, I can still ctrl-alt-F1 to switch to a text console, and from there I can manually kill Steam processes until the normal input behavior is restored back on my graphical desktop. I've found that "killall -9 steamwebhelper" always restores usability, although it's not clear to me whether one of the steamwebhelper processes itself is the culprit, or it's just that their termination causes the main Steam client to exit out of whatever loop was swallowing the input events. Since ctrl-alt- and alt-SysRq combinations are not blocked, this appears to be a blackholing of input events somewhere at the desktop layer or below, not a hardware issue or a core Xorg/display driver lockup.

steam-logs.tar.gz