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  1. Qt
  2. QTBUG-123125

QMainWindow::devicePixelRatioF() reports wrong ratio on Wayland

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Details

    • Bug
    • Resolution: Unresolved
    • P2: Important
    • None
    • 6.6.2
    • GUI: High-DPI, QPA: Wayland
    • None
    • Linux/Wayland

    Description

      On Wayland QMainWindow::devicePixelRatioF() reports a ratio of 2 when the real ratio is 1.25. On X11 the correct ratio is returned. This is the current state with the latest KDE/Plasma 6 DE.  As the Wayland merge request referenced in QTBUG-87321 was accepted and it still does not work properly in Qt6, I'm opening a new issue as it is not even clear who to blame. Was the change in Wayland not sufficient? Is it a KWin issue? Or is there still a problem in Qt?

      Anyway, from the user perspective, QMainWindow::devicePixelRatioF() is still broken in Qt6 under Wayland and at least it should be mentioned in the Qt documentation, if that can not be fixed in Qt. 

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          relates to

          Bug - A problem which impairs or prevents the functions of the product. QTBUG-113574 Incorrect sizing and bad text rendering with WebEngine using fractional scaling on Wayland

          • P1: Critical - Urgent and Important, will STOP the release if matched with set FixVersion field. This includes regressions from the last version that are not edge cases; Data loss; Build issues; All but the most unlikely crashes/lockups/hanging; Serious usability issues and embarrassing bugs & Bugs critical to a deliverable. This is the highest possible priority for requirements.
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              qt.team.graphics.and.multimedia Qt Graphics Team
              tumic Martin Tůma
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