Created attachment 104643 [details] Mouse cursor on (left) Windows decoration, (middle) Firefox bulk, and (bottom) Plasma panel I use a screen which is rotated by 90 degrees. This leads to strange DPI settings, all the text will become huge. I work around this by calling `xrandr --dpi 96` after rotating the screen. The mouse cursors are still very strange. On the Breeze decoration, it is comically oversized. Within Firefox, it has the normal size but a different shape. And on the Plasma Panel, the cursor is really large again. Resize handles are also very large. I guess this has something to do with DPI scaling. I'm using Fedora 25 with KDE Frameworks 5.32.0.
You could try setting a specific resolution in the mouse cursor theme. In general the theme is loaded based on the DPI. If you have a weird dpi, the mouse cursor might get weird. Nothing special there. Given that: hardcode the mouse cursor theme size in the config module.
Yes, that fixed it. Thanks!