Hi,

I'm still using old screen with 1280x1024. Recently i noticed that for some odd reason kwin thinks that my screen has more space on the right side than it shoud. That is:
1) If i try to maximize window, it get's placed partly outside of the screen (for instance close button may not fit in).
2) If i open new window, it also get's placed partly outside of the screen.
3) Maximized panels also are wider than screen.

I'm running kwin 5.3.2 from arch linux repos. GPU integrated with the intel i7 4790. I tried to setup rule for maximum size of the window to workaround this issue but this does not help. If i setup it for 1280 px wide, nothing changes. If i setup it for any smaller value maximized windows are aligned to the right border anyway so this does not help.

I doubt kwin "thinks" anything itr.
Check the ouput of "xrandr -q".

I assume your screen is configured for panning. We've had several reports about this (the config seemed to have been done by the kscreen daemon, but I don't recall wheter it was ever figured what and why did that)

Kwin has nothing to do with that. Other window managers had the same problems. It turned out that screen lost it's calibration. Obvious, but i didn't thinked about it since it never happend before. This topic should be closed.