Created attachment 126040 [details] screenshot of issue. Red dot is drawn at cursor position. SUMMARY This would be very easy to demonstrate with a screen recorder, unfortunately I cannot find anything that can record the screen on kde wayland. STEPS TO REPRODUCE 1. Open firefox or thunderbird in plasma wayland 2. Try to click on something 3. Both firefox and thunderbird think the mouse cursor is about -10px x -10px out of position Demo screnshot attached. I have created a test page here: https://codepen.io/Tom__B/pen/VwLeNyJ so you can see what it supposed to happen. It draws a red dot at the cursor position. As you can see in my screenshot, Firefox thinks the cursor is in a different place than it is. I had thought this affected all GTK apps but testing in GIMP, the pencil draws at exactly the correct position. Additional information: I am running a 120 font DPI which scales the UI. Perhaps it's something to do with this scaling which causes the miscalculation. SOFTWARE/OS VERSIONS Linux/KDE Plasma: 5.18.0 (available in About System) KDE Plasma Version: 5.18.0
*** This bug has been marked as a duplicate of bug 417444 ***