After watching this (rage bait) rant on Firefox gradients not doing dithering, I was left wondering ...

# compose

[Skaldebane]

After watching this (rage bait) rant on Firefox gradients not doing dithering, I was left wondering if Compose did that...

https://www.youtube.com/watch?v=mmjUlFIaNLE▾

A quick experiment (on desktop) showed that it doesn't (see image), but knowing Skia does support dithering, it wasn't all too hard to get it working 🧵

[romainguy]

Yeah all it should take is enable dithering on the paint object. Although I must say I'm bummed Skia doesn't always dither gradients. I also haven't checked what dithering Skia is using nowadays but it used to be not great (we had better dithering in Android's custom rendering pipeline for a while)

[Skaldebane]

I was just gonna do a whole writeup but.. yeah that's exactly it 😄

[Skaldebane]

The only issue to making a nice workaround for now is that ShaderBrush is only a wrapper over a Shader, so we can't get hold of the Paint and set isDither to true.

[romainguy]

(I implemented dithering in Android's rendering pipeline when we were not using Skia :)

[Skaldebane]

It would've been nice if there's was a subclass of Brush that works like SolidColor, with an applyTo function.

[Skaldebane]

Haven't actually tried this on Android, just Skiko for now
I think it would be similar? (Paint().asFrameworkPaint() then some property/function to enable dithering?)

[romainguy]

Yeah. But again, it should just always be enabled for gradients. I forget if that's what we do in Compose for Android or just Android

[Skaldebane]

Yeah exactly, as I was researching this, Flutter also enabled it by default (on both backends, Impeller and Skia) a couple years ago.

[romainguy]

Anyway so I'd suggest filing bugs or sending PRs. Don't fix it in the app

[Skaldebane]

I think API wise, that should part of the ShaderBrush class, so if somebody is doing a "gradient-like" thing with a custom brush, they could signal to whatever draws that shader into a paint that they want dithering enabled.

[Skaldebane]

Yeah ofc, I was just experimenting (and I love that I can do this at all in compose :D)

I'll fire file a feature request

[romainguy]

ShaderBrush has an applyTo

[Skaldebane]

ooh but it's final

[Skaldebane]

It's just a default implementation that takes the shader from createShader and renders it

[Skaldebane]

We can't actually override it

[romainguy]

You could subclass and override that method

[Skaldebane]

Oh wait shoot you're right

[Skaldebane]

It didn't show up in the IDE suggestions so I thought it wasn't possible 🤦

[Skaldebane]

So it is possible to workaround cleanly afterall

[romainguy]

Hmm I can't find the talk where I discuss dithering in details

[Skaldebane]

For submitting a PR, how should I go about that? Never contributed to Androidx before

[romainguy]

https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:CONTRIBUTING.md

[Skaldebane]

Oh, I was right... 😅

[Skaldebane]

that really shouldn't be final

[Skaldebane]

@romainguy those instructions seem to be geared for GitHub contributions, which don't include Compose UI (only Compose Runtime)

[Skaldebane]

Alright, found these onboarding instructions for Gerrit: https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:docs/onboarding.md
(would love Compose UI to be available on GitHub at some point; I feel so much friction to contributing already 😬)

[romainguy]

It's really not more difficult than going through GitHub but you need to do it once to understand what to do.