Created attachment 144918 [details] Resizing Discover in both axes SUMMARY When using fractional scaling (150%), vertical and horizontal lines vary between 1 and 2 pixels. STEPS TO REPRODUCE 1. Enable fractional scaling (150%) 2. Resize an app made with Kirigami (Discover) OBSERVED RESULT Line thickness changes. EXPECTED RESULT Line thickness should be constant. SOFTWARE/OS VERSIONS Operating System: KDE neon 5.23 KDE Plasma Version: 5.23.4 KDE Frameworks Version: 5.89.0 Qt Version: 5.15.3 Kernel Version: 5.11.0-43-generic (64-bit) Graphics Platform: X11 ADDITIONAL INFORMATION In the video, I am resizing Discover slowly in both axes.
Unfortunately this is just how fractional scaling works. If you take a single-pixel line and try to scale it up 150%, you end up with a 1.5 pixel line. But oops! There's no such thing as half a pixel. So the rendering engine needs to figure out how to render a 1.5px thick line on a grid of 1.0 pixels. The result depends on how the rendering engine decides to handle this, but there isn't really a good solution, just a series of trade-offs. Maybe Qt could do it better. But that would be up to Qt to fix; there isn't really anything we can do about it here in KDE land. For more information, see https://community.kde.org/Get_Involved/Design/Lessons_Learned#Pixel-alignment_for_SVG_icons, which is about a similar topic.