SUMMARY

When I move the cursor to the left edge of the screen and e.g. turn the scroll wheel, nothing happens. When I click and there are controls on the left edge of the window, nothing happens. It's as if the window manager would not consider this "one pixel column" on the left to be part of the window.

I can also see that the cursor changes, which is likely related to a different bug: all KWin context menus (when I e.g. right-click a title bar) have a bigger cursor than everything else (meaning the cursor gets bigger when it is above one of these menus), and the same bigger cursor also shows when I move it all the way to the left edge of the screen.


STEPS TO REPRODUCE
1. Log in, start e.g. a web browser.
2. Maximize the web browser, and surf to some website that gets a scroll bar.
3. Move the cursor to the left edge of the screen and turn the scroll wheel

OBSERVED RESULT

Nothing happens.

EXPECTED RESULT

The website should be scrolled.


SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: 5.14.5
KDE Frameworks Version: 5.54.0
Qt Version: 5.11.3

ADDITIONAL INFORMATION

My internal laptop screen is 4K, but I am using it with a resolution of 1920x1080. The issue occurs both with that screen and with an external screen connected via HDMI.