1738977 - Window occlusion causes pages to not render on an external monitor

Status: VERIFIED FIXED

(Core :: Widget: Win32, defect)

Description

[Chris Peterson [:cpeterson]]

@ Sotaro, this bug is a regression from enabling window occlusion in bug 1732736.

I bisected this regression to this pushlog for bug 1732736:

https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=4dc03a8a15db6385e71d7d4452bc2d24f7544a23&tochange=02ea2d15bf4c17c346aa9e06775c7027cdfacabf

In Nightly 96 build 2021-11-02, Firefox fails to load any web page. Tabs are blank/white.

I am running Windows 11 and have an external display attached to a laptop. I don't know if this is an API issue with Windows 11 or an issue with an external display. I will post my about:support info and test without my external display.

Comment 1

[Chris Peterson [:cpeterson]]

Attachment: about-support.txt

Comment 2

[Ryan VanderMeulen [:RyanVM]]

<user error>

Comment 3

[Chris Peterson [:cpeterson]]

I confirmed setting widget.windows.window_occlusion_tracking.enabled pref = false fixes the problem.

This bug only affects pages that I attempt to load in a window on my external monitor. If I drag a window that an unrendered page from my external monitor to my laptop's monitor, the unrendered page is rendered immediately.

Comment 4

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

Fixed by backout of bug 1732736. New Windows Nightlies have been requested.

Comment 6

[Sotaro Ikeda [:sotaro]]

I could reproduce the problem when 2nd display was set to main display. The problem happened on Win10 and on Win11.
Somehow, when 1st display was main display, I could not reproduce the problem on my PCs.

I am going to look into what caused the problem.

Comment 7

[Sotaro Ikeda [:sotaro]]

I found the problem and created bug 1739310.

The following code is wrong. I made a mistake during porting the ComputeNativeWindowOcclusionStatus() from chromium to gecko.

https://searchfox.org/mozilla-central/rev/88cd13997fb0747cdcd78638fc762ff2d75e1fc5/widget/windows/WinWindowOcclusionTracker.cpp#920

Comment 8

[Sotaro Ikeda [:sotaro]]

:cpeterson, can you check if the problem is addressed for you with latest nightly with pref "widget.windows.window_occlusion_tracking.enabled" == true?

Comment 9

[Chris Peterson [:cpeterson]]

(In reply to Sotaro Ikeda [:sotaro] from comment #8)

:cpeterson, can you check if the problem is addressed for you with latest nightly with pref "widget.windows.window_occlusion_tracking.enabled" == true?

widget.windows.window_occlusion_tracking.enabled == true works for me now. Thanks!

Verified fixed in Nightly 96.0a1 build 2021-11-04.

Comment 10

[Sotaro Ikeda [:sotaro]]

Good. Thank you!