1867042 - (regression) white flickering on every page reload / navigation

Status: VERIFIED FIXED

(Core :: Layout, defect, P2)

Description

[Sören Hentzschel]

Since Firefox Nightly from 2023-11-27 / the landing of the last patch in bug 1807253 there is a very annoying white flickering on every page reload or navigation on websites.

Please see the following screencast that compares Firefox 120 with the latest Nightly:

https://www.youtube.com/watch?v=T55M3VDHeXU

Comment 1

[Emilio Cobos Álvarez (:emilio)]

It's easy to reproduce using the pagination controls in https://www.camp-firefox.de/. I bisected manually and got to the same pushlog, just fwiw:

https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=9ea04a2cc829da8ce1048f38bb015b869d9273aa&tochange=95679f6ce2544b21ec9cfd0d19961058d60155d6

The page has a resize observer so it's not too unbelievable that this could've affected it...

[Tracking Requested - why for this release]: Seems in some circumstances after that bug paint suppression is broken and we pain the new page too early.

Comment 2

[Emilio Cobos Álvarez (:emilio)]

Okay, I took a quick poke and it seems we're initializing the pres shell too early from:

PresShell::Initialize(https://www.camp-firefox.de/?sortField=time&sortOrder=DESC&pageNo=4)#01: mozilla::PresShell::Initialize() (/home/emilio/src/moz/gecko-2/layout/base/PresShell.cpp:1719)
#02: nsContentSink::StartLayout(bool) (/home/emilio/src/moz/gecko-2/dom/base/nsContentSink.cpp:610)
#03: mozilla::dom::Document::FlushPendingNotifications(mozilla::ChangesToFlush) (/home/emilio/src/moz/gecko-2/dom/base/Document.cpp:10843)
#04: mozilla::dom::BrowsingContext::PreOrderWalkVoid(std::function<void (mozilla::dom::BrowsingContext*)> const&) (/home/emilio/src/moz/gecko-2/docshell/base/BrowsingContext.cpp:1191)
#05: mozilla::dom::Document::DetermineProximityToViewportAndNotifyResizeObservers() (/home/emilio/src/moz/gecko-2/dom/base/Document.cpp:17186)
#06: nsRefreshDriver::DetermineProximityToViewportAndNotifyResizeObservers() (/home/emilio/src/moz/gecko-2/layout/base/nsRefreshDriver.cpp:2266)
#07: nsRefreshDriver::Tick(mozilla::layers::BaseTransactionId<mozilla::VsyncIdType>, mozilla::TimeStamp, nsRefreshDriver::IsExtraTick) (/home/emilio/src/moz/gecko-2/layout/base/nsRefreshDriver.cpp:2762)
#08: mozilla::detail::RunnableFunction<nsRefreshDriver::EnsureTimerStarted(nsRefreshDriver::EnsureTimerStartedFlags)::$_1>::Run() (/home/emilio/src/moz/gecko-2/obj-debug/dist/include/nsThreadUtils.h:549)
#09: mozilla::RunnableTask::Run() (/home/emilio/src/moz/gecko-2/xpcom/threads/TaskController.cpp:550)
#10: mozilla::TaskController::DoExecuteNextTaskOnlyMainThreadInternal(mozilla::detail::BaseAutoLock<mozilla::Mutex&> const&) (/home/emilio/src/moz/gecko-2/xpcom/threads/TaskController.cpp:876)
#11: mozilla::TaskController::ExecuteNextTaskOnlyMainThreadInternal(mozilla::detail::BaseAutoLock<mozilla::Mutex&> const&) (/home/emilio/src/moz/gecko-2/xpcom/threads/TaskController.cpp:0)
#12: mozilla::TaskController::ProcessPendingMTTask(bool) (/home/emilio/src/moz/gecko-2/xpcom/threads/TaskController.cpp:485)
#13: mozilla::detail::RunnableFunction<mozilla::TaskController::TaskController()::$_0>::Run() (/home/emilio/src/moz/gecko-2/xpcom/threads/nsThreadUtils.h:549)
#14: nsThread::ProcessNextEvent(bool, bool*) (/home/emilio/src/moz/gecko-2/xpcom/threads/nsThread.cpp:1202)
#15: NS_ProcessNextEvent(nsIThread*, bool) (/home/emilio/src/moz/gecko-2/xpcom/threads/nsThreadUtils.cpp:480)
#16: mozilla::ipc::MessagePump::Run(base::MessagePump::Delegate*) (/home/emilio/src/moz/gecko-2/ipc/glue/MessagePump.cpp:85)
#17: MessageLoop::Run() (/home/emilio/src/moz/gecko-2/ipc/chromium/src/base/message_loop.cc:346)
#18: nsBaseAppShell::Run() (/home/emilio/src/moz/gecko-2/widget/nsBaseAppShell.cpp:150)
#19: nsAppShell::Run() (/home/emilio/src/moz/gecko-2/widget/gtk/nsAppShell.cpp:427)
#20: XRE_RunAppShell() (/home/emilio/src/moz/gecko-2/toolkit/xre/nsEmbedFunctions.cpp:721)
#21: mozilla::ipc::MessagePumpForChildProcess::Run(base::MessagePump::Delegate*) (/home/emilio/src/moz/gecko-2/ipc/glue/MessagePump.cpp:235)
#22: MessageLoop::Run() (/home/emilio/src/moz/gecko-2/ipc/chromium/src/base/message_loop.cc:346)
#23: XRE_InitChildProcess(int, char**, XREChildData const*) (/home/emilio/src/moz/gecko-2/toolkit/xre/nsEmbedFunctions.cpp:660)
#24: main (/home/emilio/src/moz/gecko-2/browser/app/nsBrowserApp.cpp:375)

We probably don't want to trigger pres shell initialization from that code.

Comment 3

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1867042 - Don't force PresShell initialization from ResizeObserver handling. r=fredw,#layout

This is unfortunately somewhat hard to test, because paint suppression
is not really quite observable by the page.

This makes sure that we don't report resize observations etc until the
page has been laid out for other reasons.

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/7aca76ceb374
Don't force PresShell initialization from ResizeObserver handling. r=fredw

Comment 5

[Natalia Csoregi [:nataliaCs]]

https://hg.mozilla.org/mozilla-central/rev/7aca76ceb374

Comment 6

[Daniel Bodea [:danibodea]]

I can't seem to reproduce this issue on an old MacBook Air with MacOS 11 using Nightly v122.0a1 from 2023-11-27 and 2023-11-28. No white flicker was observed when reloading webpage https://www.camp-firefox.de/. This being said, I can not verify this fix using this system.

Comment 7

[Sören Hentzschel]

This being said, I can not verify this fix using this system.

I can verify that the reported issue no longer happens.

Comment 8

[Catalin Sasca, Desktop Test Engineering [:csasca]]

Reproduced the issue on Firefox 122.0a1 (2023-11-28) on macOS 13.6.3 by following the infos provided in Comment 0.

The issue is fixed on Firefox 122.0a1 (2023-11-30) and 123.0a1 (2024-01-21) on the same machine.