wip cleanup ViewFactory.showRendering

Author: zach-klippenstein

core-compose/src/main/java/com/squareup/workflow/ui/compose/internal/ForkedViewStub.kt

@@ -15,17 +15,20 @@
  */
 package com.squareup.workflow.ui.compose.internal
 
-import android.content.Context
-import android.view.ViewGroup.LayoutParams.MATCH_PARENT
-import android.widget.FrameLayout
+import android.view.View
 import androidx.compose.Composable
+import androidx.compose.onPreCommit
+import androidx.compose.remember
+import androidx.ui.core.ContextAmbient
 import androidx.ui.core.Modifier
+import androidx.ui.core.Ref
 import androidx.ui.foundation.Box
+import androidx.ui.viewinterop.AndroidView
 import com.squareup.workflow.ui.ViewEnvironment
 import com.squareup.workflow.ui.ViewFactory
-import com.squareup.workflow.ui.WorkflowViewStub
+import com.squareup.workflow.ui.canShowRendering
 import com.squareup.workflow.ui.compose.ComposeViewFactory
-import com.squareup.workflow.ui.compose.internal.ComposableViewStubWrapper.Update
+import com.squareup.workflow.ui.showRendering
 
 /**
  * Renders [rendering] into the composition using the `ViewRegistry` from the [ViewEnvironment] to
@@ -53,46 +56,36 @@ import com.squareup.workflow.ui.compose.internal.ComposableViewStubWrapper.Updat
     // view system and can just invoke the binding's composable function directly.
     if (viewFactory is ComposeViewFactory) {
       viewFactory.showRenderingWrappedWithRoot(rendering, viewEnvironment)
-    } else {
-      // Plumb the current composition "context" through the ViewEnvironment so any nested
-      // composable factories get access to any ambients currently in effect.
-      // See setOrContinueContent().
-      val newEnvironment = viewEnvironment.withParentComposition()
+      return@Box
+    }
 
-      // IntelliJ currently complains very loudly about this function call, but it actually
-      // compiles. The IDE tooling isn't currently able to recognize that the Compose compiler
-      // accepts this code.
-      ComposableViewStubWrapper(update = Update(rendering, newEnvironment, this))
+    val (childView, newEnvironment) = createChildView(viewFactory, rendering, viewEnvironment)
+    onPreCommit(childView, newEnvironment, rendering) {
+      childView.showRendering(rendering, newEnvironment)
     }
+    AndroidView(childView)
   }
 }
 
-/**
- * Wraps a [WorkflowViewStub] with an API that is more Compose-friendly.
- *
- * In particular, Compose will only generate `Emittable`s for views with a single constructor
- * that takes a [Context].
- *
- * See [this slack message](https://kotlinlang.slack.com/archives/CJLTWPH7S/p1576264533012000?thread_ts=1576262311.008800&cid=CJLTWPH7S).
- */
-private class ComposableViewStubWrapper(context: Context) : FrameLayout(context) {
-
-  data class Update(
-    val rendering: Any,
-    val viewEnvironment: ViewEnvironment,
-    val viewFactory: ViewFactory<Any>
-  )
-
-  private val viewStub = ForkedViewStub(context)
-
-  init {
-    addView(viewStub)
-  }
-
-  // Compose turns this into a parameter when you invoke this class as a Composable.
-  fun setUpdate(update: Update) {
-    viewStub.update(update.rendering, update.viewEnvironment, update.viewFactory)
-  }
+@Composable private fun <R : Any> createChildView(
+  viewFactory: ViewFactory<R>,
+  rendering: R,
+  viewEnvironment: ViewEnvironment
+): Pair<View, ViewEnvironment> {
+  val childView = remember { Ref<View>() }
+  val newEnvironment = if (childView.value?.canShowRendering(rendering) != true) {
+    // Plumb the current composition "context" through the ViewEnvironment so any nested
+    // composable factories get access to any ambients currently in effect.
+    // See setOrContinueContent().
+    viewEnvironment.withParentComposition()
+        .also { newEnvironment ->
+          childView.value = viewFactory.buildView(
+              initialRendering = rendering,
+              initialViewEnvironment = newEnvironment,
+              contextForNewView = ContextAmbient.current
+          )
+        }
+  } else viewEnvironment
 
-  override fun getLayoutParams(): LayoutParams = LayoutParams(MATCH_PARENT, MATCH_PARENT)
+  return Pair(childView.value!!, newEnvironment)
 }