Created attachment 8748617 [details] oddContentSize.PNG Firefox 47.0b1 on Windows 10 (not eligible for e10s experiment, tabs.remote.autostart is false) I woke my laptop out of sleep, moved my Firefox window with many tabs to my external lodpi display, and used the "stretch the window to the top" method to snap the window full-height. New tabs and some old tabs are correctly-sized, but all of my bugzilla tabs' content areas are smaller than the actual tab content size. The window was never this dimension (that I recall) so maybe it's a default value.
Jonathan, do we know about this on 47? Is this just something we still need to uplift a fix for from 48 or something? Chris, is this reliably reproducible?
I'm afraid I don't know if it is reproducible. I'm up to my armpits in tasks today, so I'm unfortunately not in a position to experiment :S
I'd say the tab is exactly 1/4 of the area it should be, suggesting that your hi- and lo-dpi displays probably have scale factors of 200% and 100% respectively, and the bounds were mis-scaled somewhere. Does the problem resolve itself if you move the window back and forth between displays again (triggering additional DPI-changed notifications)? This looks oddly similar to bug 1248675, which was fixed fairly recently (and uplifted to 46 and 47), but that was an OS X-specific issue; I wonder if the Windows widget code has a similar problem? Reliable STR would be really valuable here.
Simply resizing the window was enough to kick it back into gear. And, correct, the laptop's hidpi display is 2x and the lodpi external display is 1x. The window moves back and forth between displays every evening as I disconnect/reconnect. Add that to how only the bugzilla tabs were affected, and I'm not sure that there will be reliable STR...
I may have STR: 1) Set up your two-display, mixed DPI setup, with your Firefox on the external lodpi. (My setup: Lenovo X1 Carbon, Windows 10, using HDMI to connect to a budget AOC display) 2) Pull the plug on the external display. (simply turning it off doesn't work as, though Windows succeeds at being dumb enough to believe that the display is disconnected when it turns itself off, it has too much notice to adjust its desktop size) 3) Put the plug back in. I have successfully made background tabs of wikimo, dxr, some MDN pages, and gcal be wrong-sized with these steps. Helpful?
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