Flutter has a UI component `BackdropFilter` that lets you do kotlinlang #compose

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]

02/27/2020, 9:53 PM

i think you could build this with public API today

could be wrong though

Zach Klippenstein (he/him) [MOD]

02/27/2020, 10:03 PM

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

Leland Richardson [G]

02/27/2020, 10:18 PM

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]

02/27/2020, 10:20 PM

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

Maybe i missed something in the canvas API

Leland Richardson [G]

02/27/2020, 10:28 PM

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

Chris Craik

02/27/2020, 10:52 PM

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

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

Zach Klippenstein (he/him) [MOD]

02/27/2020, 11:34 PM

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

02/28/2020, 1:50 AM

BlurMaskFilter also doesn’t blur the content

Zach Klippenstein (he/him) [MOD]

02/28/2020, 2:26 AM

Yea, it just fades the alpha along the edges

romainguy

02/28/2020, 4:08 AM

Well it blurs alpha :)

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