Closed Bug 859266 Opened 8 years ago Closed 8 years ago

[win-hidpi] fullscreen window incorrectly sized with custom devPixelsPerPx value


(Core :: Widget: Win32, defect)

Windows 7
Not set



Tracking Status
firefox22 --- fixed
firefox23 --- fixed


(Reporter: jfkthame, Assigned: jfkthame)


(Blocks 1 open bug)



(1 file)

Since bug 824386 landed, fullscreen windows are handled correctly with default settings (layout.css.devPixelsPerPx = -1.0, i.e. respect system settings). 

However, if the user sets a custom devPixelsPerPx value, fullscreen mode (F11) does not work correctly - the window will be too small if devPixelsPerPx is 1.0 but the system scaling is 125% or 150%, for example, and too large if devPixelsPerPx is increased beyond the system value.

This is because widget/windows/nsWindow.cpp respects the custom devPixelsPerPx value when positioning/sizing windows, but nsScreenWin.cpp relies on the system value when determining the available size of the screen(s).

It's possible to fix this by handling the discrepancy in nsBaseWidget::MakeFullScreen, by comparing GetDefaultScale() with the value returned by GetDefaultScaleInternal() and using the ratio (if different) as a correction factor. However, I think it's cleaner to fix it by making nsScreenWin respect the devPixelsPerPx preference in the same way as nsWindow, so that the two will always agree about coordinates.

(Users who don't mess with about:config settings will never see the problem, of course, as the default is for GetDefaultScale to return the system value so everything agrees anyway. But unless/until we're prepared to completely remove the devPixelsPerPx override, we should fix the issue here.)
Blocks: win-hidpi
Patch to make nsScreenWin etc respect the scaling pref. AFAICT, this makes fullscreen mode, window-position constraints, etc work properly for both default and custom devPixelsPerPx settings.

Tryserver build:
Attachment #734551 - Flags: review?(roc)
Closed: 8 years ago
Resolution: --- → FIXED
Duplicate of this bug: 854385
This needs to be landed on aurora branch too.
Comment on attachment 734551 [details] [diff] [review]
patch, convert nsScreenWin etc to respect devPixelsPerPx setting

[Approval Request Comment]
Bug caused by (feature/regressing bug #): win-hidpi support

User impact if declined: incorrectly-sized "fullscreen" window for users who set custom devPixelsPerPx value different from the system-level scaling

Testing completed (on m-c, etc.): in Nightly

Risk to taking this patch (and alternatives if risky): low risk - no impact for users with default prefs

String or IDL/UUID changes made by this patch: none
Attachment #734551 - Flags: approval-mozilla-aurora?
Comment on attachment 734551 [details] [diff] [review]
patch, convert nsScreenWin etc to respect devPixelsPerPx setting

We won't track for release since this is nonstandard, but it seems worth the uplift.
Attachment #734551 - Flags: approval-mozilla-aurora? → approval-mozilla-aurora+
Keywords: verifyme
mass remove verifyme requests greater than 4 months old
Keywords: verifyme
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