[iOS] Flashing white area at the top of the screen when swiping a page containing platform views

[0xZOne]

Steps to Reproduce

1. git clone -b task/displaylink git@github.com:0xZOne/platform_view_performance.git
2. cd platform_view_performance
3. flutter run
4. As shown in the video below

RPReplay_Final1675046104.MP4

flutter doctor -v

[✓] Flutter (Channel stable, 3.7.0, on macOS 13.1 22C65 darwin-x64, locale zh-Hans-CN)
    • Flutter version 3.7.0 on channel stable at /Users/zero/fvm/versions/3.7.0
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision b06b8b2710 (6 days ago), 2023-01-23 16:55:55 -0800
    • Engine revision b24591ed32
    • Dart version 2.19.0
    • DevTools version 2.20.1
    • Pub download mirror https://pub.flutter-io.cn
    • Flutter download mirror https://storage.flutter-io.cn

[✓] Android toolchain - develop for Android devices (Android SDK version 33.0.1)
    • Android SDK at /Users/zero/Library/Android/sdk
    • Platform android-33, build-tools 33.0.1
    • ANDROID_HOME = /Users/zero/Library/Android/sdk
    • Java binary at: /Applications/Android Studio.app/Contents/jre/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 11.0.13+0-b1751.21-8125866)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 14.2)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 14C18
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[✓] Android Studio (version 2021.3)
    • Android Studio at /Applications/Android Studio.app/Contents
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    • Java version OpenJDK Runtime Environment (build 11.0.13+0-b1751.21-8125866)

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[✓] Connected device (1 available)
    • 艾尔玛的iPhone (2) (mobile) • 00008110-001A30960238401E • ios • iOS 15.5 19F77

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• No issues found!

[jmagman]

@0xZOne what's the exception?

[0xZOne]

@0xZOne what's the exception?

Flashing white area at the top of the screen when swiping as shown.

[cyanglaz]

@0xZOne Does it only happen on pro-motion devices?

[chinmaygarde]

From Triage: Our guess is that there are frames in succession where a platform is and isn't in the scene. The thread merge and un-merge is probably causing on frame to not be displayed with -[CALayer setPresentsWithTransation:YES] for a single frame which causes the mismatch.

[cyanglaz]

From Triage: Our guess is that there are frames in succession where a platform is and isn't in the scene. The thread merge and un-merge is probably causing on frame to not be displayed with -[CALayer setPresentsWithTransation:YES] for a single frame which causes the mismatch.

Should be easily verified by turning on -[CALayer setPresentsWithTransation:YES] always.

[chinmaygarde]

Should be easily verified by turning on -[CALayer setPresentsWithTransation:YES] always.

You could try that but I don't think we always have a transaction when off the main thread. In case no one pushes a transaction, we may deadlock. Advising caution.

[0xZOne]

@0xZOne Does it only happen on pro-motion devices?

I'm not sure, but I only encountered it on ProMotion devices.

[cyanglaz]

Some observations:

1. I couldn't reproduce it on an iPhone XS (non-pro-motion)
2. It is less likely reproducible in release mode.
3. turning on -[CALayer setPresentsWithTransation:YES] on raster thread didn't resolve the issue, which makes sense after looking at the example again. The example app always has at least 1 platform view in the scene so there are no un-merge.

[cyanglaz]

It could be related: #118366

[hellohuanlin]

In case it's helpful - I encountered an issue that I suspect it is related to this.

I tried out the example code in #86787. When using the latest main branch, it looks like the top area becomes transparent, so the platform view underneath is displayed (pic below). The release build is fine.

[timtangcoding]

In case it's helpful - I encountered an issue that I suspect it is related to this.

I tried out the example code in #86787. When using the latest main branch, it looks like the top area becomes transparent, so the platform view underneath is displayed (pic below). The release build is fine.

Same observation found (#116640 (comment)), The native view will move up to top bar even if SafeArea is used.

[timtangcoding]

Some observations:

1. I couldn't reproduce it on an iPhone XS (non-pro-motion)
2. It is less likely reproducible in release mode.
3. turning on -[CALayer setPresentsWithTransation:YES] on raster thread didn't resolve the issue, which makes sense after looking at the example again. The example app always has at least 1 platform view in the scene so there are no un-merge.

So far I only found this issues on Pro devices. I found such issues appear on iPhone 13 Pro and iPhone 14 Pro. However, on iPhone 11 Pro there is no such issue.

[cyanglaz]

So far I only found this issues on Pro devices. I found such issues appear on iPhone 13 Pro and iPhone 14 Pro. However, on iPhone 11 Pro there is no such issue.

It looks like an issue related to the pro-motion display. (iPhone 13 pro and iPhone 14 pro are the only iPhones support pro-motion)

[ristiisa]

I can repro this on 6s and simulator in addition to 11 pro and 14 pro and 15 pro max.

please see #142801