1237660 - Window size is incorrect when switching tabs/ returning to firefox on OSX (El Capitan)

Status: UNCONFIRMED

(Core :: Layout, defect)

Description

[me]

Attachment: Screen Shot 2016-01-07 at 17.00.21.png

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:43.0) Gecko/20100101 Firefox/43.0
Build ID: 20160105164030

Steps to reproduce:

Switch tabs or switch back to Firefox application from another application.



Actual results:

The window appears smaller than the actual firefox window. Once the bug occurs it then occurs for all tabs, the window will return to the proper size if you refresh a page, but if you switch tabs back to the page again, the bug will occur again.


Expected results:

The content size in the window should always match the window size.

Comment 1

[Boris Zbarsky [:bzbarsky]]

This happens randomly, I assume, not on every tab switch?

It looks like the content is 2x smaller than it should be.  Is that correct?  If so, is this a high-dpi screen?  Or are there multiple monitors some of which are high-dpi and some are not?

Comment 2

[me]

Ah good catch Boris, one of my screens is high-dpi and my secondary screen is not.
It seems that once I have a window that has been open for a certain amount of time (and flicking through several open tabs), dragging the window from my primary screen (high-dpi) to my secondary screen will cause the bug to occur, and the displayed windows size is always 0.5x the size it should be.

It also now looks like once a window has gotten into this state, when I drag it from my low Dpi screen to my High Dpi screen, the reverse will happen. The content window appears to be twice the size of my actual window. (Added screen shot)

Comment 3

[me]

Attachment: Dragging from Low Dpi to High Dpi

Comment 4

[Boris Zbarsky [:bzbarsky]]

roc, do you recall offhand who's worked on issues with multiple different-dpi screens?

Comment 5

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Jonathan Kew. Thanks Jonathan :-)

Comment 6

[Jonathan Kew [:jfkthame]]

Looks suspiciously like we might sometimes be missing/losing a windowDidChangeBackingProperties or windowDidChangeScreen notification to the nsCocoaWindow; or perhaps the UIResolutionChanged() call to the prescontext (which we handle asynchronously with a runnable) is failing somehow.

I'll hook up an external display for a while and see if I can reproduce this with any consistency... leaving needinfo? flag as a reminder.