Paparazzi detection

[emartynov]

I saw that AsyncImagePainter is working differently in Previews.

Should we do something similar with Paparazzi? We can detect it by next check Build.FINGERPRINT.contains("layoutlib").

[ychescale9]

To give user more control and avoid implicit coupling with layoutlib perhaps we could have a SynchronousImageLoader in coil-test?

This is mainly relevant when loading vector drawable with AsyncImage though:

AsyncImage(
    model = R.my_drawable,
    contentDescription = null,
)

For urls AsyncImagePreviewHandler and FakeImageLoaderEngine still make more sense.

[colinrtwhite]

By default Coil requests inside Paparazzi will run the same as on a real device. To have everything run synchronously you can set ImageLoader.Builder.coroutineContext(EmptyCoroutineContext). Coil does this automatically if LocalInspectionMode.current is true, but Paparazzi doesn't set that.

Should we do something similar with Paparazzi? We can detect it by next check Build.FINGERPRINT.contains("layoutlib")

Maybe? I'm a little apprehensive to do this as LocalInspectionMode.current can be controlled by the user at the call site. Build.FINGERPRINT is a static class and it's value is fixed - there's no way to override it locally. Additionally, if we do this for Paparazzi we should probably also handle it for Roborazzi.

So far I think my recommendation is to either:

• Set CompositionLocalProvider(LocalInspectionMode provides true) in your tests. This is probably the easiest.
• Set ImageLoader.Builder.coroutineContext(EmptyCoroutineContext) on the ImageLoader used in your tests. At Cash App we inject a "fake" ImageLoader that sets this so everything runs synchronously.
• Use FakeImageEngine to set a custom response. This won't jump to a background thread.