Window bleeds 1 pixel to the left of where it should be

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Steps to reproduce:

  • Have two 1920*1080 screens, arranged horizontally next to each other.
  • Open a non-maximised application (let’s say Dolphin)
  • Half-tile the window to occupy the left half of the right-hand monitor
    • Alternatively, use kdotool windowmove to position it at (1920, 0) - the issue isn’t specific to using the tiling feature

The problem is that a 1-pixel-wide strip of the window bleeds onto the left-hand monitor.

Further observations:

  • “No window borders” is set in the Window Decorations settings.
  • Using the KWin Debug Console shows that the window’s pos is indeed (1920, 0) - i.e. the very top-left hand corner of the right-hand monitor, as it should be.
  • This doesn’t happen if the window is maximised.

This started happening fairly recently, but I’m sorry I can’t pinpoint exactly when. I suspect it wasn’t in Plasma 6.4, but I’m not sure if it’s always been there in 6.5, or if some 6.5.x release introduced it.

My kinfo:

Operating System: Fedora Linux 43
KDE Plasma Version: 6.5.4
KDE Frameworks Version: 6.21.0
Qt Version: 6.10.1
Kernel Version: 6.17.12-300.fc43.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 5700X 8-Core Processor
Memory: 32 GiB of RAM (31.3 GiB usable)
Graphics Processor: NVIDIA GeForce RTX 3060 Ti
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