Border around video when going fullscreen from non-maximized window on secondary monitor




Widget: Win32
2 years ago
2 years ago


(Reporter: Chris Borrell, Unassigned, NeedInfo)


51 Branch
Windows 10

Firefox Tracking Flags

(Not tracked)



(1 attachment)



2 years ago
User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:51.0) Gecko/20100101 Firefox/51.0
Build ID: 20160910030426

Steps to reproduce:

Windows 10, ATI graphics with multi-monitor setup.

1. Open new FF window. Move to secondary monitor and maximize.

2. Browse to a HTML5-based video (have reproduced with both Youtube, Twitch, and Air Mozilla). For the purposes of reproducing I was watching

3. Move browser window (without resizing) so that half the window is offscreen (but still on the secondary monitor)

4. Double-click the video (or use player control) to fullscreen video.

Actual results:

Video is full-screened on second monitor as expected, but the left, right and bottom edges of the video have a 6px gap around the edge (windows below the video are visible in this gap).

Expected results:

Video should be full-screened with no gaps between the video and edge of the screen.


2 years ago
OS: Unspecified → Windows 10
Hardware: Unspecified → x86_64

Comment 1

2 years ago
Have also noted that the issue only presents if the window has not been resized in it's lifetime. if any point the window is resized (before or after loading the page with the video), the issue doesn't seem to occur.

Comment 2

2 years ago
Created attachment 8790082 [details]
Video capture describing and demonstrating the issue

Comment 3

2 years ago
Is it a recent issue in FF51? Did you observe it in past versions of Firefox like 48 or older?
Flags: needinfo?(borrell)

Comment 4

2 years ago
Honestly I've just switched to FF from Chrome for my video needs, so I'm not sure when the issue might have started.

However I just tried and was able to reproduce in 48.0.2

Comment 5

2 years ago
Jonathan, do you know someone able too look at this issue on a multi-monitor setup?
Component: Untriaged → Widget: Win32
Flags: needinfo?(borrell) → needinfo?(jfkthame)
Product: Firefox → Core
I'm guessing this is a Win10-only issue, maybe related to the way Windows does something a bit weird with window border/padding metrics, in order to provide a draggable area for resizing the window by its edges even though there isn't a thick, obviously-grabbable border like Win8 used to have. In effect, I think they give the window an invisible but nevertheless grabbable border area. But offhand I don't know why this exact scenario shows the glitch, while other variations (e.g. after resizing the window) don't.

I'll leave the needinfo? flag to remind me to try and reproduce this, though it seems a sufficiently obscure edge-case (sorry!) that it may not get immediate attention. Or maybe :emk or :xidorn would have some insight; I'll cc them as well.

Comment 7

2 years ago
No problems! It's not really a big issue. I'm going to do a bit more digging around circumstances and reproduction when I get a chance - thoughts at the moment include

- (prompted by your comment) is the window border invisible, or is the fullscreen video rendered at a smaller size?
- try a few older versions of FF and see if it is a regression from some point
- different monitor configurations (e.g. secondary monitor in different positions related to primary monitor)
- video drivers

and see if there's anything of interest.
See Also: → bug 1302168

Comment 8

2 years ago
I'm unable to reproduce this again (build 52.0a1 20161104030212).

Happy for this bug to be closed (or invalid/wontfix - not sure what the convention is here).
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