Maybe the inverse of <#C04TPPEQKEJ|compose-android...

# compose-android

[Colton Idle]

Maybe the inverse of #compose-android, but I'm trying to move this file to compose multiplatform. The issue is with

import android.graphics.Matrix

https://gist.github.com/KlassenKonstantin/d5f6ed1d74b3ddbdca699d66c6b9a3b2

Is there a compose version of Matrix that has postRotate?

[romainguy]

So you want a multiplatform matrix?

[Colton Idle]

I suppose so? I'm basically just using that gist that someone has for creating a cool but fake fluid-eque background. thought itd be simple enough to put that into multiplatform, but i guess not.I do see import androidx.compose.ui.graphics.Matrix, but it doesn't seem to have postRotate available. so idk if its just something completely different.

[romainguy]

All the rotate functions are post-rotate functions on that class

[romainguy]

but if you want something more general, you can use this library I wrote (and it’s KMP ready): https://github.com/romainguy/kotlin-math

[romainguy]

pre/post rotate is just a matter of the order of the operations

[romainguy]

rotate(…) * matrix vs matrix * rotate(…)

[Colton Idle]

cool.
alright. i have no idea what im doing. but i converted

val matrix = Matrix().apply {
postRotate(angle, size.width / 2, size.height / 2)
}

to
val matrix = Matrix().apply {
rotateX(angle)
}

[Colton Idle]

i also cant seem to call shader.setLocalMatrix. 🤔

[romainguy]

That's an Android specific API

[Colton Idle]

gotcha. i guess i dont need a multiplatform gradient animation that bad. ill just use a static gradient. lol

[romainguy]

but you can do it with regular Compose APIs

[romainguy]

you could rotate the rectangles for instance

[romainguy]

@Nader Jawad, we don’t have another way to apply a transform to a shader brush right?

[Nader Jawad]

setLocalMatrix is not yet exposed on the ShaderBrush API but you can use the Android shader APIs and create a ShaderBrush from that

[Nader Jawad]

I think you would want rotateZ to rotate content within the same plane

[Colton Idle]

but if i wanted to do it in a multiplatform way... then theres no way to do that currently?

[romainguy]

Right so that’s where instead you can rotate your drawRect()

[Colton Idle]

interesting. ill timebox this for a few more minutes and see if i can get something. thanks for the inspiration