Can't capture the output of a BackdropFilterLayer without painting it to the screen #170792
Description
Steps to reproduce
For my implementation of Liquid Glass I need a way to capture an image of a BackdropFilterLayer to pass into my shader, but the image shouldn't actually be painted to the screen.
What I've tried is the same approach I use to paint foreground masks:
// Semi-pseudo code
class MyLayer extends ContainerLayer {
@override
void addToScene(SceneBuilder builder) {
// I can't capture an image of this scene without the builder being invalid afterwards
super.addToScene(builder);
}
Image captureBlurredBackground() {
// And this way, the actual current background is not included in the scene.
final builder = ui.SceneBuilder()..pushBackdropFilter(ImageFilter.shader(shader));
return builder.build().toImageSync(100, 100);
}
}However, this builder doesn't actually pick up on the Backdrop of the scene that the app is built in.
I also couldn't find any way to capture the scene that is being built in addToScene.
Expected results
I should be able to capture the output of a BackdropFilterLayer without having to paint it to the screen.
Actual results
I can't :)
Code sample
see above
Screenshots or Video
No response
Logs
No response
Flutter Doctor output
Doctor output
[✓] Flutter (Channel stable, 3.32.4, on macOS 15.5 24F74 darwin-arm64, locale en-US)
[✓] Android toolchain - develop for Android devices (Android SDK version 35.0.0)
[✓] Xcode - develop for iOS and macOS (Xcode 16.4)
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! Error: Browsing on the local area network for iPhone von mir. Ensure the
device is unlocked and attached with a cable or associated with the same local
area network as this Mac.
The device must be opted into Developer Mode to connect wirelessly. (code -27)
! Error: Browsing on the local area network for Tim’s iPad. Ensure the device is
unlocked and attached with a cable or associated with the same local area
network as this Mac.
The device must be opted into Developer Mode to connect wirelessly. (code -27)
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Issues that are less important to the Flutter projectNothing broken; request for a new capabilityA detailed proposal for a change to Flutterflutter/engine related. See also e: labels.flutter/packages/flutter repository. See also f: labels.Owned by Engine teamTriaged by Engine teamThe Flutter team cannot make further progress on this issue until the original reporter responds