SUMMARY After going from Qt 6.9 to 6.10 back in June 2025, I noticed that the KWin 'Window Behaviour' / 'Window placement' setting seems to be completely ignored for Qt applications, and new windows will open at 0,0, or in other words, top-left of the left-most screen on a three-screen set-up running X11. Perhaps likely a Qt bug, or at least changed behaviour, but filing here first for visibility and such until I get to look deeper into the matter myself. STEPS TO REPRODUCE 1. Run KWin X11 on LXQt in a three-display set-up (probably should see this on full Plasma, and single-display set-up too). 2. Set 'Window placement' to anything other than 'top-left corner'. 3. Make sure 'Allow apps to remember the psoitions of their own windows, if they support it' is disabled. 4. Run a Qt application, something like 'kcalc' for example, and observe it being placed at 0,0, or top-left corner instead of, for example, randomly or centred. OBSERVED RESULT New Qt application windows always appear at 0,0, or top-left corner, if they don't remember their last position. EXPECTED RESULT Windows are placed according to the KWin 'Window placement' setting. SOFTWARE/OS VERSIONS Linux/KDE Plasma: Gentoo Linux (Not a full Plasma install, but using KWin with LXQt.) KDE Plasma Version: 6.4.3 KDE Frameworks Version: 6.16.0 Qt Version: 6.10 (838d543cd2adddce6419faa91647192653d71088) ADDITIONAL INFORMATION Wayland behaviour not tested at all.
Thank you for the bug report! However Plasma 6.3.5 no longer receives updates or maintenance from KDE; active versions are 6.4 or newer. Please upgrade to an active version as soon as your distribution makes it available to you. Plasma is a fast-moving project, and bugs in one version are often fixed in the next one. If you need help with Plasma 6.3.5, please contact your distribution, who bears the responsibility of providing help for older releases that are no longer receiving updates from KDE. If you can reproduce the issue after upgrading to an active version, feel free to re-open this bug report.
I suppose the "version first reported in" is a bit confusing to me here. Re-opening as this is happening with a current release still.
Likely a Qt bug indeed. Were you ever able to report it to the Qt folks or investigate it there?
Unfortunately no, have not gotten to it yet.
Since Qt 6.10.0 landed in the Arch Linux repositories, I have noticed my "Minimal Overlapping" window placement setting stopped working and always position themselves in the top-left corner. Can confirm this bug under X11, single HiDPI monitor user. Doesn't happen on Wayland. Applications affected in particular: Dolphin, Konsole, KWrite, Kate, System Settings, Info Centre. It doesn't seem to be just KDE apps, my own Qt 6 app ends up positioned at 0,0 too if the app is configured to "let the window manager decide". My workaround is to add a window rule to "Ignore requested geometry" = "Yes" for these applications, then it's back to normal. Strangely, the dialog box for KWrite's "Close Document - Saved Changes?" prompt ends up in the top-left too, but Kate's version centers as expected.
Confirmed as a Qt bug. Link to related bug report over on qt.io for reference/tracking: https://bugreports.qt.io/browse/QTBUG-141099
*** Bug 510566 has been marked as a duplicate of this bug. ***
Same problem here on Arch Linux. As I can understand it's up to the Qt team and not KDE?
(In reply to kaminata from comment #8) > Same problem here on Arch Linux. As I can understand it's up to the Qt team > and not KDE? Yes. You can follow https://bugreports.qt.io/browse/QTBUG-141099 if you would like to track their progress.
(In reply to TraceyC from comment #9) > (In reply to kaminata from comment #8) > > Same problem here on Arch Linux. As I can understand it's up to the Qt team > > and not KDE? > > Yes. You can follow https://bugreports.qt.io/browse/QTBUG-141099 if you > would like to track their progress. Thank you very much!