Flutter has a UI component `BackdropFilter` that l...

# compose

[Zach Klippenstein (he/him) [MOD]]

Flutter has a UI component BackdropFilter that lets you do stuff like blur whatever’s behind a view. I know that effect isn’t part of the Material spec, but is something like that possible (or potentially possible in the future) with Compose?

[Leland Richardson [G]]

i think you could build this with public API today

[Leland Richardson [G]]

could be wrong though

[Zach Klippenstein (he/him) [MOD]]

I haven’t seen anything in the API that looked obvious, but i might be thinking about it wrong

[Leland Richardson [G]]

i think if you used Draw (and in the future, the draw modifier), you get raw access to the canvas and i think you could apply a filter there

[Zach Klippenstein (he/him) [MOD]]

The flutter implementation has a bunch of components that manipulate “layers” (presumably hardware layers?). Draw(Modifier) only give you access to your own children, not the layer below you, I think?

https://github.com/flutter/flutter/blob/2132a0c7a3d2a107190238ca0c5570baa0467bb7/packages/flutter/lib/src/rendering/proxy_box.dart#L1064-L1073

[Zach Klippenstein (he/him) [MOD]]

Maybe i missed something in the canvas API

[Leland Richardson [G]]

this might be relevant to some of the rendernode work we are doing

[Chris Craik]

Android canvas doesn't really expose any blurring, other than BlurMaskFilter, which isn't supported for most operations

[Chris Craik]

At least on most versions of the platform, not sure about recent ones

[Zach Klippenstein (he/him) [MOD]]

Yea, I was playing with BlurMaskFilter but it only lets you blur the current layer. I was wondering if this would require explicit RenderNode support.

[romainguy]

BlurMaskFilter also doesn’t blur the content

[Zach Klippenstein (he/him) [MOD]]

Yea, it just fades the alpha along the edges

[romainguy]

Well it blurs alpha :)