Previously in both kwin and plasmashell the "QT_DEVICE_PIXEL_RATIO" var are unset. Now qt 5.6 deprecated "QT_DEVICE_PIXEL_RATIO" and use "QT_AUTO_SCREEN_SCALE_FACTOR" instead. I solved the problem locally by adding "qunsetenv("QT_AUTO_SCREEN_SCALE_FACTOR");" to both kwin and plasmashell. Reproducible: Always Steps to Reproduce: 1. Upgrade qt to 5.6-beta or later. 2. Set QT_AUTO_SCREEN_SCALE_FACTOR=1 in the env Actual Results: Kwin and plasmashell run into an unusable state. Other kde-apps works fine (konsole, dolphin). Expected Results: Kwin and plasmashell work normally.
I think we should instead set the officially supported Qt::AA_DisableHighDpiScaling flag on the QApplication.
Git commit bb3e7c47f4a5d0104756c515e2fa1920b5c726b1 by David Edmundson. Committed on 19/01/2016 at 12:05. Pushed by davidedmundson into branch 'Plasma/5.5'. Keep disabling Qt's high DPI when on Qt 5.6 M +3 -1 shell/main.cpp http://commits.kde.org/plasma-workspace/bb3e7c47f4a5d0104756c515e2fa1920b5c726b1
Doing so, though it's not completely ideal as it'll be broke from whenever you upgrade between Qt5.6 at runtime and plasma gets recompiled.
Thanks very much. I just rebuild with master again and it works properly now. How about Kwin, shall we have a similar change there?
Git commit 90112ef0cd6ed33f28b657f59d1cd3196077e955 by David Edmundson. Committed on 26/01/2016 at 17:01. Pushed by davidedmundson into branch 'Plasma/5.5'. Use new Qt flag to disable high DPI scaling on X This flag was set for main_wayland but not X. REVIEW: 126810 M +3 -0 main_x11.cpp http://commits.kde.org/kwin/90112ef0cd6ed33f28b657f59d1cd3196077e955
Why does plasmashell set Qt::AA_DisableHighDpiScaling? This gives it tiny fonts for me (high dpi screen, QT_SCALE_FACTOR=2)