New BigPicture mode is not properly exiting to Desktop Mode for Mesa 22.3

[ranplayer]

• Steam client version (build number or date): Dec 1 2022
• Distribution (e.g. Ubuntu): ArchLinux
• Opted into Steam client beta?: [Yes/No] No
• Have you checked for system updates?: [Yes/No] Yes

Please describe your issue in as much detail as possible:

• New BigPicture mode is not properly exiting to Desktop Mode for Mesa 22.3.1 (works normally for 22.2.3). It seems to keep two windows opened (one with the big picture and another for the desktop)

Steps for reproducing this issue:

1. Start the Steam client with the param -newbigpicture
2. Click on the option to go back to desktop mode

[ranplayer]

Update: tested with Mesa 22.3.3 and Kernel 6.1.5. This issue only happens if you exit to desktop mode using a mouse (with the gamepad it works fine)

[Goggo66]

I confirm this behaviour for

• Steam client version (build number or date): 1673573268
• Distribution (e.g. Ubuntu): Kubuntu
• Opted into Steam client beta?: [Yes/No] Yes
• Have you checked for system updates?: [Yes/No] Yes
• Mesa: 23.0-git2301050600.d045b3-oibaf

It is not limited to ArchLinux only.

Please describe your issue in as much detail as possible:

When leaving new BigPicture mode, there are two windows: the normal Steam client window, and another X window (presumably the one for the previous BigPicture mode), which is minimized. The window is labeled "steamwebhelper", "SP". It cannot be easily closed from the taskbar (right mouse click -> "Close"). Opening this window results in a messed up display with whatever was on the screen at that point in time. The window can only be killed by: pressing Ctrl-Alt-Esc, and then clicking into the window.

Steps for reproducing this issue:

1. Open Steam in desktop mode.
2. Activate BigPicture mode.
3. Leave BigPicture mode via STEAM menu (bottom left), and "On/Off"
4. Observe the two windows, as described above.