Support loading placeholders in compose previews

Composable placeholders already worked, but resource and drawable
placeholders did not. Presumably some part of the production codepath
isn't supported by the Android Studio renderer. The actual display of
the resources seems to work fine, we just never get to that point in
Glide's code. Debugging exactly what's happening seems mostly
impossible. I don't see a way to view logs or debug code running in the
Android Studio preview renderer.

For now we can work around whatever the issue is by rendering resources
and drawables when in preview mode earlier than normal.

Author: sjudd

integration/compose/src/main/java/com/bumptech/glide/integration/compose/GlideImage.kt

@@ -15,6 +15,7 @@ import androidx.compose.ui.graphics.DefaultAlpha
 import androidx.compose.ui.layout.ContentScale
 import androidx.compose.ui.layout.layout
 import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.platform.LocalInspectionMode
 import androidx.compose.ui.semantics.SemanticsPropertyKey
 import androidx.compose.ui.semantics.SemanticsPropertyReceiver
 import androidx.compose.ui.semantics.semantics
@@ -28,6 +29,7 @@ import com.bumptech.glide.integration.ktx.InternalGlideApi
 import com.bumptech.glide.integration.ktx.ResolvableGlideSize
 import com.bumptech.glide.integration.ktx.Size
 import com.bumptech.glide.integration.ktx.Status
+import com.google.accompanist.drawablepainter.rememberDrawablePainter
 
 /** Mutates and returns the given [RequestBuilder] to apply relevant options. */
 public typealias RequestBuilderTransform<T> = (RequestBuilder<T>) -> RequestBuilder<T>
@@ -111,6 +113,14 @@ public fun GlideImage(
   val overrideSize: Size? = requestBuilder.overrideSize()
   val (size, finalModifier) = rememberSizeAndModifier(overrideSize, modifier)
 
+  // TODO(judds): It seems like we should be able to use the production paths for
+  // resource / drawables as well as Composables. It's not totally clear what part of the prod code
+  // isn't supported.
+  if (LocalInspectionMode.current && loading?.isResourceOrDrawable() == true) {
+    PreviewResourceOrDrawable(loading, contentDescription, modifier)
+    return
+  }
+
   SizedGlideImage(
     requestBuilder = requestBuilder,
     size = size,
@@ -125,6 +135,27 @@ public fun GlideImage(
   )
 }
 
+@OptIn(ExperimentalGlideComposeApi::class)
+@Composable
+private fun PreviewResourceOrDrawable(
+  loading: Placeholder,
+  contentDescription: String?,
+  modifier: Modifier,
+) {
+  val drawable =
+    when(loading) {
+      is Placeholder.OfDrawable -> loading.drawable
+      is Placeholder.OfResourceId -> LocalContext.current.getDrawable(loading.resourceId)
+      is Placeholder.OfComposable ->
+        throw IllegalArgumentException("Composables should go through the production codepath")
+    }
+  Image(
+    painter = rememberDrawablePainter(drawable),
+    modifier = modifier,
+    contentDescription = contentDescription,
+  )
+}
+
 /**
  * Used to specify a [Drawable] to use in conjunction with [GlideImage]'s `loading` or `failure`
  * parameters.
@@ -177,6 +208,13 @@ public sealed class Placeholder {
   internal class OfResourceId(@DrawableRes internal val resourceId: Int) : Placeholder()
   internal class OfComposable(internal val composable: @Composable () -> Unit) : Placeholder()
 
+  internal fun isResourceOrDrawable() =
+    when (this) {
+      is OfDrawable -> true
+      is OfResourceId -> true
+      is OfComposable -> false
+    }
+
   internal fun maybeComposable(): (@Composable () -> Unit)? =
     when (this) {
       is OfComposable -> this.composable