Bug 470155

SUMMARY
After bringing a window forward by clicking on a task manager item and leaving the mouse pointer there, plasmashell does not show a window thumbnail tooltip, but the underlying screencast session keeps running.

STEPS TO REPRODUCE
1. Open some windows. Ideally, also open qpwgraph to visualize PipeWire connections
2. Move the mouse pointer to the task manager, click on an item to open another window, and leave the pointer there

OBSERVED RESULT
The thumbnail window may briefly appear, but in qpwgraph, the screencast connection exists until the mouse pointer moves away.

EXPECTED RESULT
The screencast connection may need to be closed as soon as the window thumbnail disappears.

SOFTWARE/OS VERSIONS
Operating System: Arch Linux 
KDE Plasma Version: 5.27.5
KDE Frameworks Version: 5.106.0
Qt Version: 5.15.9
Kernel Version: 6.3.3-arch1-1 (64-bit)
Graphics Platform: Wayland

ADDITIONAL INFORMATION
In my system, this running screencast connection triggers a lot of logs in the journal like these:

kwin_wayland[1312]: kwin_screencast: Dropping a screencast frame because the compositor is slow

Makes me think that it affects system performance to some extent, but neither kwin_wayland nor pipewire uses any noticeable CPU or GPU time (but why does it think the compositor is too slow?).