1246382 - layout.css.devPixelsPerPx > 1 shrinks FireFox's full screen viewable area

Status: RESOLVED FIXED

(Firefox :: Untriaged, defect)

Description

[Anonymous]

User Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:47.0) Gecko/20100101 Firefox/47.0
Build ID: 20160205030204

Steps to reproduce:

1. Use about:config to change property "layout.css.devPixelsPerPx" to a value greater than 1.

2. Attempt to go into full screen through any means (ex: Press F11, watching a YouTube video in full screen mode, etc.) and the actual full screen viewable area will be a shrunken size.

The shrunken size seems to be a width and height roughly equal to 1 / (value of devPixelsPerPx). In other words, using a devPixelsPerPx value of 2, the full screen viewable area is 1/2 width and 1/2 height, leading to a 1/4 viewable size.


Actual results:

Full screen viewable area shrinks.


Expected results:

Full screen viewable area should NOT shrink. Full screen should always be the _full_ screen, regardless of the scaling used with "devPixelsPerPx".

This used to work correctly until a few weeks ago.

Comment 1

[Alice0775 White]

[Tracking Requested - why for this release]: Regression of fullscreen visual layout


Pushlog:
https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=98756a36223c1a2b51cd0368736b728429038caf&tochange=a9f9b36c1a2eec7626e6b749e46ab0a8bf3323e2

Regressed by: Bug 890156

Comment 2

[Jonathan Kew [:jfkthame]]

Attachment: Screen rect in desktop pixels should not be affected by devPixelsPerPx override

Comment 3

[Masatoshi Kimura [:emk]]

Comment on attachment 8716913 [details] [diff] [review]
Screen rect in desktop pixels should not be affected by devPixelsPerPx override

Review of attachment 8716913 [details] [diff] [review]:
-----------------------------------------------------------------

::: widget/windows/nsScreenWin.cpp
@@ +114,5 @@
>    nsresult rv = GetRect(&left, &top, &width, &height);
>    if (NS_FAILED(rv)) {
>      return rv;
>    }
> +  double scaleFactor = 1.0 / widget::WinUtils::LogToPhysFactor(mScreen);

Is this correct when per-monitor DPI is enabled? I thought devPix == deskPix if per-monitor DPI is enabled.
See also bug 1246346.

Comment 4

[Jonathan Kew [:jfkthame]]

Comment on attachment 8716913 [details] [diff] [review]
Screen rect in desktop pixels should not be affected by devPixelsPerPx override

Review of attachment 8716913 [details] [diff] [review]:
-----------------------------------------------------------------

::: widget/windows/nsScreenWin.cpp
@@ +114,5 @@
>    nsresult rv = GetRect(&left, &top, &width, &height);
>    if (NS_FAILED(rv)) {
>      return rv;
>    }
> +  double scaleFactor = 1.0 / widget::WinUtils::LogToPhysFactor(mScreen);

If per-monitor DPI is enabled, we take the early return at the start of this method; this code is not used.

Comment 5

[Masatoshi Kimura [:emk]]

Comment on attachment 8716913 [details] [diff] [review]
Screen rect in desktop pixels should not be affected by devPixelsPerPx override

Oh, I understand.

Comment 6

[Jonathan Kew [:jfkthame]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/2ae52d49a5b104ce74fd9dd71865affbe4f8871a
Bug 1246382 - Screen rect in desktop pixels should not be affected by devPixelsPerPx override. r=emk

Comment 7

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/2ae52d49a5b1

Comment 8

[Liz Henry (:lizzard) (relman/hg->git project)]

Jonathan, want to request uplift for this to aurora? 
Tracking since it's a recent regression.

Comment 9

[Jonathan Kew [:jfkthame]]

This should be fixed on current aurora by the backout of bug 890156.

Comment 10

[Mayur Patil]

[bugday-20160323]

Status: RESOLVED,FIXED -> VERIFIED

Comments:
Test Successful

Component: 
Name			Firefox
Version			46.0b9
Build ID		20160322075646
Update Channel          beta
User Agent		Mozilla/5.0 (Windows NT 6.1; WOW64; rv:46.0) Gecko/20100101 Firefox/46.0
OS			Windows 7 SP1 x86_64

Expected Results: 
Yes, for value 2.0 also fullscreen size same as that of -1.0.

Actual Results: 
As expected