1361758 - [W8.1] White artifacts on left and right extremities of Fx when switching between low and high resolution screens

Status: NEW

(Core :: Widget: Win32, defect, P3)

Description

[Bogdan Maris, Desktop QA]

Attachment: Screenshot showing the issue

[Affected versions]:
- Firefox 53.0
- Firefox 54 beta 4
- latest Nightly 55.0a1

[Affected platforms]:
- Windows 8.1 only (Windows 10 is not affected)

[Steps to reproduce]:

Prerequisites:
- Make sure to select the middle value from Control Panel\Display\Screen Resolution\Make text and other items larger or smaller. (I think that's 150% value). Sign out and sign back in afterwards. Have two screens, one low res and one high dpi. I used WSXGA Samsung 2233 and Dell UHD-1 P2415Qb monitors.

1. Start Firefox
2. Move the browser to the low res screen.
3. Change the size of the text and items (I changed it one value to the right, I think that's 200% - which is also the recommended value for this monitor). 
4. Don't sign out. Move the browser to high res screen.

[Expected result]:
- No graphical issues are seen.

[Actual result]:
- White lines can be seen on the left and right extremities.

[Regression range]:
- This is a regression, not a recent one though. Here is the output from mozregression:

Narrowed inbound regression window from [fdfb1d87, c3771535] (3 revisions) to [14593086, c3771535] (2 revisions) (~1 steps left)
Using url: https://hg.mozilla.org/integration/mozilla-inbound/json-pushes?changeset=c3771535a47ebb8260de3362188c83790831867e&full=1

Pushlog_url: https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=7452e706f98556cec41158761f700b84d726ec98&tochange=75582480f7824c82d82e5b6111cccd1066cb0745

Found commit message:

Bug 1289143 - Apply the appropriate scaling to window edges when processing WM_NCCALCSIZE for a window on a secondary screen with non-system DPI. r=emk


[Additional notes]:
- This issue is Windows 8.1 only, I did not encountered the same behavior on Windows 10.

Comment 1

[Gerry Chang [:gchang]]

Too late for 54, let's see if we can fix it in 55.

Comment 2

[Mike Taylor [:miketaylr]]

Jim, do you think this is important for 57? Seems kinda polish-y.

Comment 3

[Jim Mathies [:jimm]]

We have a lot of dual screen issues. This impacts 8.1 only so my guess is it's a side effect related to the new dpi per screen apis we use in win10 not being available on 8.1.