Created attachment 162612 [details]
screenshot of the bug

SUMMARY
In some cases (not clear what the complete conditions are), when a window title "foo bar's bar" does not fit in the task manager such that it should get shortened as "foo bar..." I instead see just "foo".

Encountered in the wild on https://forums.spacebattles.com/threads/a-young-girls-game-of-thrones.1095557/

STEPS TO REPRODUCE
1. Make a window whose title starts with "A Young Girl's Game" (eg by entering a directory with this name in a shell in konsole)
2. Open enough windows to crowd the task manager (unset window grouping to make this easier) (10 windows including the one with the tested title works for me, but this probably depends on screen resolution, font settings, and how much stuff is in the system tray etc)
3. Observe the bug

OBSERVED RESULT
Window title is cut off earlier than it should be, leaving noticeable blank space (see attached file bad.png)

EXPECTED RESULT
Window title should be cut off later (see attached file good.png, produced by replacing the ' with a - in the window title)

SOFTWARE/OS VERSIONS

KDE Plasma Version: 5.27.8
KDE Frameworks Version: 5.107.0
Qt Version: 5.15.10

ADDITIONAL INFORMATION