Any built-in way to determine if a `@Composable` is being presented in a `@Preview` or not? (Somethi...

# compose

[darkmoon_uk]

Any built-in way to determine if a @Composable is being presented in a @Preview or not? (Something in Locals?)
I know it shouldn't care; but sometimes in the real world there are practical reasons.
In this case the Coil SVG library is crashing in Previews for some class-loader related reason; I need some flag to suppress registering of the SVG handler in Previews so I can get on with building the rest of the View.

[Andrew Neal]

https://coil-kt.github.io/coil/compose/#localimageloader

[darkmoon_uk]

@Andrew Neal I don't think I need help using Coil - not sure how linking to that doco answers my question. Coil is already integrated and I'm using LocalImageLoader - Coils SVG renderer is just exhibiting an incompatibility with `Preview`s right now, and I need something like an isRunningInPreviewMode flag to suppress it.

[Ian Lake]

You're looking for https://developer.android.com/reference/kotlin/androidx/compose/ui/platform/package-summary#LocalInspectionMode()

[darkmoon_uk]

Thank you @Ian Lake 🎉

[Andrew Neal]

Are you not able to use a dummy LocalImageLoader in your preview to avoid loading the SVG?

[Ian Lake]

Yeah, what Andrew is suggesting is providing your own LocalImageLoader specifically wrapping the components you want to preview that is essentially a no-op / has preview specific behavior. That way your component itself doesn't need to know about whether it is in a preview or not

[darkmoon_uk]

Thanks, yes, that's close to what I'm intending 👍 - I'm already providing my own LocalImageLoader from a top-level @Composable scope and identified that it's enough to just not register the SVG handler during its configuration. The rest of Coil's ImageLoader isn't a problem, and no components need to be aware; SVG's just won't be handled.

[darkmoon_uk]

I'll try and dig into the issue the SVG Component has with Previews in a bit, and raise an appropriate issue. Unclear whether that would be with Coil or Compose atm.

[darkmoon_uk]

(It's a `java.lang.NoClassDefFoundError: Could not initialize class coil.decode.SvgDecoder`even though that class is defined in the implementation classpath in Gradle and runtime is OK 🤷).

[darkmoon_uk]

Workaround is working, went with providing a full 'dummy' ImageLoader in the end; thanks Andrew & Ian ⭐

[yschimke]

I like your approach, I ended up conditionally setting a placeholder but I think I'll switch to your way.

It seems worth raising a bug for SVG failing in previews.

fun rememberAstronautPainter(person: Assignment?) =
    rememberImagePainter(person?.personImageUrl) {
        // Use the generic astronaut SVG for missing or error (404?).
        fallback(R.drawable.ic_american_astronaut)
        error(R.drawable.ic_american_astronaut)

        if (LocalInspectionMode.current) {
            // Show error image instead of blank in @Preview
            placeholder(R.drawable.ic_american_astronaut)
        }
    }

[darkmoon_uk]

Did you see the same issue as above with SVG in Preview, @yschimke?

[yschimke]

No, but I have remote images which don't download in previews