Firefox after restart breaks it's forced size and becomes larger or smaller in width/height for several pixels. gtk-precompiled firefox binaries in Linux Mint & Calculate Linux. Happens seldom. Sometimes cuts off several pixels from the right. Sometimes becomes large in the bottom Reproducible: Sometimes
> Sometimes cuts off several pixels from the right. Sometimes becomes large in the bottom That means FF attempts to resize itself, shits on size passed by the WM in return of the configure request and happily resizes *it's content* to the assumed size. If the decoration has the proper size we can assume that the client (the managed window) has the correct size as well (determining a gap here will require you to recompile kwin with some debug output but it is really highly unlikely that the framesize does not match the managed client size) Feel free to illustrate the observed issue with a screenshot and outputs of "xwininfo" and "xprop" but from what i understand, this is a firefox internal issue (unawareness that a configure request can be altered or ignored altogether by the WM)