Is a non-zero `blurRadius` required for `Shadow` to be visible? I am just trying to use shadow in a ...

# compose

[Chris Fillmore]

Is a non-zero blurRadius required for Shadow to be visible? I am just trying to use shadow in a TextStyle. If I don’t specify a non-zero blur radius, there is no shadow. This seems unexpected. I’d expect to be able to use shadow without blur. I’m on compose 1.2.0-alpha02

[Chris Sinco [G]]

cc @Siyamed @Sean McQuillan [G]

[Siyamed]

can you please create a ticket?

[Chris Fillmore]

Sure, will do tomorrow morning

[Siyamed]

https://developer.android.com/reference/android/graphics/Paint#setShadowLayer(float,%20float,%20float,%20int)

[Siyamed]

this seems to be a very old behavior in android. Therefore I am not sure if it would be possible to change. it.

[Siyamed]

“If radius is 0, then the shadow layer is removed.”

[Siyamed]

possibly we need to change the default blur value maybe

[Siyamed]

CSS does support 0blur radius

[Siyamed]

https://developer.mozilla.org/en-US/docs/Web/CSS/box-shadow

[Siyamed]

I wonder what @Nader Jawad thinks

[Chris Fillmore]

I have filed https://issuetracker.google.com/issues/219552739

[Nader Jawad]

I think this is WAI. You are specifying the radius of the shadow in this case. If you pass 0 then no shadow will be rendered

[Nader Jawad]

What would the expected behavior be for a bout radius of 0? It wouldn't be different than specifying a composable with 0 width/height and having it not draw at all

[Chris Fillmore]

Correct me if I’m wrong but doesn’t the radius only apply to the blur?

[Chris Fillmore]

A radius of 0 just means no blur, not no shadow.

At least that’s how I would interpret that

[Nader Jawad]

That indicates the size, so zero would be zero here

[Nader Jawad]

That is nothing would be rendered

[Chris Fillmore]

Ok thanks for responding. Feel free to close the ticket.

I suppose as a workaround one could just create two Text nodes, one of them with an offset. If no-blur shadow was desired.

[Nader Jawad]

That would work if you just wanted to offset the content

[Chris Fillmore]

I’m not sure I follow what you mean. What is the content you’re referring to, just the text?

[Nader Jawad]

Yes the text in this case

[Chris Fillmore]

Ok. Yeah to be clear all I mean is:

val text = "my text"
Text(
  text = text,
  modifier = Modifier.offset(-4f, 4f),
)
Text(
  text = text,
)

I think this should produce a basic shadow with no blur

[Nader Jawad]

Yup that seems reasonable

[Siyamed]

Or provide a very small blur?

[Siyamed]

Would it work?

[Siyamed]

Nader what does blur mean for graphics? Css defines it the bluering of the shadow it seems

[Nader Jawad]

I don't think that was what the API was intended for to be honest. It looks more like the OP was looking to render the same exact content just rendered offset slightly which is different from a shadow

[Nader Jawad]

CSS can generate shadows that are not consistent from a physical standpoint. Android + compose have a single light source for shadows which keeps them consistent and updates in real time based on where the UI element is relative to the light source itself

[Siyamed]

With my zero knowledge of graphics, distance is the offset in this use case

[Siyamed]

Would android render shadow with i.e. 0.1f blur?

[Nader Jawad]

So to be clear here the shadows that I was referring to are the RenderNode based shadows as part of Modifier.graphicsLayer the shadow API that is used on text is part of Paint.setShadowLayer which behaves differently. The latter actually existed before the former however has had different levels of support as Android evolved from being software rendered to hardware rendered and moving away from and back to Skia as the underlying graphics framework

[Siyamed]

thanks

[Chris Fillmore]

Yeah thanks for the context!

[Chris Sinco [G]]

CSS can generate shadows that are not consistent from a physical standpoint

While this is true, the reality is many designer tools and other UI toolkits on other platforms handle shadows this way (not the Android single-light source way), so it’s reasonable to have this confusion with Android development when the mockup says “build this shadow but make it hard and not blurry” and the APIs + rendered results look different.