+++ This bug was initially created as a clone of Bug #1502062 +++ > User Agent: Mozilla/5.0 (Windows NT 10.0; rv:64.0) Gecko/20100101 > Firefox/64.0 > > Steps to reproduce: > > When I exit from a fullscreen video it doesn't respect the position or size > of my browser window, resulting in tiled windows being overlapped, as well > as firefox by itself if positioned to the edges of the screen (not snapped) > being forced inward by about 10px on the top, bottom, and right. > > --- snipped --- > > Actual results: > > example 1: No edge snapping used, Window positioned in the top-right corner > of the screen manually, winds up being shoved inward. This one hurts me the > most because on my normal setup I have the window positioned at about 65% > width on one of my screens, with 100% of the vertical space being used. > https://webmshare.com/VPmwz > > example 2: normal window snapped to the left, with Firefox snapped to the > right, restoring from fullscreen causes the browser window to expand by > 10px, causing it to overflow onto the other window thus breaking tiling. > https://webmshare.com/oQrBQ > > example 2a: another issue I've encountered with the second example is that > not only does it expand by 10px, it never stops expanding... what I mean is, > for every time you do the transition from fullscreen the browser will gain > 10px width every time. > https://webmshare.com/ZQD1d Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:65.0) Gecko/20100101 Firefox/65.0 Build ID: 20181129095546 Only case 1 is caused by and fixed-by-backing-out bug 1473816. As for case 2, I can still reproduce it after another (probably unrelated) snapping bug 1482920 is fixed. Steps to reproduce: (Please refer to the attached video. WARNING: RAPID FLASHING due to rapid fullscreen-ing) 1. Do not maximize Nightly window. 2. Snap it to the left, right, or top. 3. F11 to enter and exit fullscreen. 4. Observe the window size. Actual result: Nightly's window size expands. Some content are extended out of the screen. Note: IIRC, this may be a long standing bug that was present before Windows 10 1809(Redstone 5) update but I do not have a machine with 1803 to confirm.

I can confirm this is the case with Win_10 1809 (OS Build 18262.100) and FFX 65.0a1(2018-12-02). Not reproducible on my workstation which has Win_10 1803 (OS Build 17134.407).