BREAKING: Compose overhaul makes ViewEnvironment less in your face.

* Introduces `LocalWorkflowEnvironment` and eliminates explicit `ViewEnvironment` parameters from `ScreenComposableFactory.Content`, `ComposeScreen.Content`, etc. It is put in place automatically by the default implementation of `ScreenComposableFactoryFinder`.

* Adds optional `CompositionRoot` argument to `ViewEnvironment.withComposeInteropSupport()`. `CompositionRoot` is our existing hook to ensure `CompositionLocal`s (e.g. for UI themes) are put in play above the `@Composable Content()` function invoked for any `Screen`.

* Replaces `ViewEnvironment.withCompositionRoot` with `@Composable fun ViewEnvironment.RootScreen`, as our preferred Compose-friendly alternative to `WorkflowLayout`

An `Activity` that uses `setContent {}` instead of `setContentView` can now kick things off like so:

```kotlin
  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)

    val environment : ViewEnvironment = ViewEnvironment.EMPTY +
      // ...
      .withComposeInteropSupport()

    val rootScreen by RootWorkflow.renderAsState(
      props = Unit,
      onOutput = {},
    )

    setContent {
      environment.RootScreen(rootScreen)
    }
  }
```

samples/compose-samples/src/main/java/com/squareup/sample/compose/hellocompose/App.kt

@@ -30,7 +30,6 @@ private val viewEnvironment = ViewEnvironment.EMPTY.withComposeInteropSupport()
     )
     WorkflowRendering(
       rendering,
-      viewEnvironment,
       Modifier.border(
         shape = RoundedCornerShape(10.dp),
         width = 10.dp,

samples/compose-samples/src/main/java/com/squareup/sample/compose/hellocompose/HelloComposeScreen.kt

@@ -8,7 +8,6 @@ import androidx.compose.runtime.Composable
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.tooling.preview.Preview
-import com.squareup.workflow1.ui.ViewEnvironment
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow1.ui.compose.ComposeScreen
 import com.squareup.workflow1.ui.compose.tooling.Preview
@@ -18,7 +17,7 @@ data class HelloComposeScreen(
   val message: String,
   val onClick: () -> Unit
 ) : ComposeScreen {
-  @Composable override fun Content(viewEnvironment: ViewEnvironment) {
+  @Composable override fun Content() {
     Text(
       message,
       modifier = Modifier

samples/compose-samples/src/main/java/com/squareup/sample/compose/hellocomposebinding/HelloBinding.kt

@@ -13,7 +13,7 @@ import com.squareup.workflow1.ui.compose.ScreenComposableFactory
 import com.squareup.workflow1.ui.compose.tooling.Preview
 
 @OptIn(WorkflowUiExperimentalApi::class)
-val HelloBinding = ScreenComposableFactory<Rendering> { rendering, _ ->
+val HelloBinding = ScreenComposableFactory<Rendering> { rendering ->
   Text(
     rendering.message,
     modifier = Modifier

samples/compose-samples/src/main/java/com/squareup/sample/compose/hellocomposebinding/HelloBindingActivity.kt

@@ -18,7 +18,6 @@ import com.squareup.workflow1.ui.ViewRegistry
 import com.squareup.workflow1.ui.WorkflowLayout
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow1.ui.compose.withComposeInteropSupport
-import com.squareup.workflow1.ui.compose.withCompositionRoot
 import com.squareup.workflow1.ui.plus
 import com.squareup.workflow1.ui.renderWorkflowIn
 import com.squareup.workflow1.ui.withEnvironment
@@ -27,10 +26,9 @@ import kotlinx.coroutines.flow.StateFlow
 @OptIn(WorkflowUiExperimentalApi::class)
 private val viewEnvironment =
   (ViewEnvironment.EMPTY + ViewRegistry(HelloBinding))
-    .withCompositionRoot { content ->
+    .withComposeInteropSupport { content ->
       MaterialTheme(content = content)
     }
-    .withComposeInteropSupport()
 
 /**
  * Demonstrates how to create and display a view factory with

samples/compose-samples/src/main/java/com/squareup/sample/compose/hellocomposeworkflow/ComposeWorkflow.kt

@@ -7,7 +7,6 @@ import com.squareup.workflow1.Sink
 import com.squareup.workflow1.StatefulWorkflow
 import com.squareup.workflow1.Workflow
 import com.squareup.workflow1.WorkflowIdentifier
-import com.squareup.workflow1.ui.ViewEnvironment
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow1.ui.compose.ComposeScreen
 
@@ -35,17 +34,15 @@ abstract class ComposeWorkflow<in PropsT, out OutputT : Any> :
 
   /**
    * Renders [props] by emitting Compose UI. This function will be called to update the UI whenever
-   * the [props] or [viewEnvironment] change.
+   * the [props] change.
    *
    * @param props The data to render.
    * @param outputSink A [Sink] that can be used from UI event handlers to send outputs to this
    * workflow's parent.
-   * @param viewEnvironment The [ViewEnvironment] passed down through the `ViewBinding` pipeline.
    */
   @Composable abstract fun RenderingContent(
     props: PropsT,
     outputSink: Sink<OutputT>,
-    viewEnvironment: ViewEnvironment
   )
 
   override fun asStatefulWorkflow(): StatefulWorkflow<PropsT, *, OutputT, ComposeScreen> =
@@ -62,14 +59,12 @@ inline fun <PropsT, OutputT : Any> Workflow.Companion.composed(
   crossinline render: @Composable (
     props: PropsT,
     outputSink: Sink<OutputT>,
-    environment: ViewEnvironment
   ) -> Unit
 ): ComposeWorkflow<PropsT, OutputT> = object : ComposeWorkflow<PropsT, OutputT>() {
   @Composable override fun RenderingContent(
     props: PropsT,
     outputSink: Sink<OutputT>,
-    viewEnvironment: ViewEnvironment
   ) {
-    render(props, outputSink, viewEnvironment)
+    render(props, outputSink)
   }
 }

samples/compose-samples/src/main/java/com/squareup/sample/compose/hellocomposeworkflow/ComposeWorkflowImpl.kt

@@ -10,7 +10,6 @@ import com.squareup.workflow1.Snapshot
 import com.squareup.workflow1.StatefulWorkflow
 import com.squareup.workflow1.action
 import com.squareup.workflow1.contraMap
-import com.squareup.workflow1.ui.ViewEnvironment
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow1.ui.compose.ComposeScreen
 
@@ -39,12 +38,12 @@ internal class ComposeWorkflowImpl<PropsT, OutputT : Any>(
       propsHolder,
       sinkHolder,
       object : ComposeScreen {
-        @Composable override fun Content(viewEnvironment: ViewEnvironment) {
+        @Composable override fun Content() {
           // The sink will get set on the first render pass, which must happen before this is first
           // composed, so it should never be null.
           val sink = sinkHolder.sink!!
           // Important: Use the props from the MutableState, _not_ the one passed into render.
-          workflow.RenderingContent(propsHolder.value, sink, viewEnvironment)
+          workflow.RenderingContent(propsHolder.value, sink)
         }
       }
     )

samples/compose-samples/src/main/java/com/squareup/sample/compose/hellocomposeworkflow/HelloComposeWorkflow.kt

@@ -16,7 +16,6 @@ import com.squareup.sample.compose.hellocomposeworkflow.HelloComposeWorkflow.Tog
 import com.squareup.workflow1.Sink
 import com.squareup.workflow1.WorkflowExperimentalRuntime
 import com.squareup.workflow1.config.AndroidRuntimeConfigTools
-import com.squareup.workflow1.ui.ViewEnvironment
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow1.ui.compose.WorkflowRendering
 import com.squareup.workflow1.ui.compose.renderAsState
@@ -34,7 +33,6 @@ object HelloComposeWorkflow : ComposeWorkflow<String, Toggle>() {
   @Composable override fun RenderingContent(
     props: String,
     outputSink: Sink<Toggle>,
-    viewEnvironment: ViewEnvironment
   ) {
     MaterialTheme {
       Text(
@@ -57,5 +55,5 @@ fun HelloComposeWorkflowPreview() {
     onOutput = {},
     runtimeConfig = AndroidRuntimeConfigTools.getAppWorkflowRuntimeConfig()
   )
-  WorkflowRendering(rendering, ViewEnvironment.EMPTY)
+  WorkflowRendering(rendering)
 }

samples/compose-samples/src/main/java/com/squareup/sample/compose/inlinerendering/InlineRenderingWorkflow.kt

@@ -22,7 +22,6 @@ import com.squareup.workflow1.WorkflowExperimentalRuntime
 import com.squareup.workflow1.config.AndroidRuntimeConfigTools
 import com.squareup.workflow1.parse
 import com.squareup.workflow1.ui.Screen
-import com.squareup.workflow1.ui.ViewEnvironment
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow1.ui.compose.ComposeScreen
 import com.squareup.workflow1.ui.compose.WorkflowRendering
@@ -60,7 +59,7 @@ fun InlineRenderingWorkflowRendering() {
     onOutput = {},
     runtimeConfig = AndroidRuntimeConfigTools.getAppWorkflowRuntimeConfig()
   )
-  WorkflowRendering(rendering, ViewEnvironment.EMPTY)
+  WorkflowRendering(rendering)
 }
 
 @Preview(showBackground = true)

samples/compose-samples/src/main/java/com/squareup/sample/compose/nestedrenderings/NestedRenderingsActivity.kt

@@ -19,24 +19,22 @@ import com.squareup.workflow1.ui.ViewRegistry
 import com.squareup.workflow1.ui.WorkflowLayout
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow1.ui.compose.withComposeInteropSupport
-import com.squareup.workflow1.ui.compose.withCompositionRoot
 import com.squareup.workflow1.ui.plus
 import com.squareup.workflow1.ui.renderWorkflowIn
 import com.squareup.workflow1.ui.withEnvironment
 import kotlinx.coroutines.flow.StateFlow
 
 @OptIn(WorkflowUiExperimentalApi::class)
-private val viewRegistry = ViewRegistry(RecursiveViewFactory)
+private val viewRegistry = ViewRegistry(RecursiveComposableFactory)
 
 @OptIn(WorkflowUiExperimentalApi::class)
 private val viewEnvironment =
   (ViewEnvironment.EMPTY + viewRegistry)
-    .withCompositionRoot { content ->
+    .withComposeInteropSupport { content ->
       CompositionLocalProvider(LocalBackgroundColor provides Color.Green) {
         content()
       }
     }
-    .withComposeInteropSupport()
 
 @WorkflowUiExperimentalApi
 class NestedRenderingsActivity : AppCompatActivity() {

samples/compose-samples/src/main/java/com/squareup/sample/compose/nestedrenderings/RecursiveViewFactory.kt

@@ -24,22 +24,21 @@ import androidx.compose.ui.tooling.preview.Preview
 import com.squareup.sample.compose.R
 import com.squareup.sample.compose.nestedrenderings.RecursiveWorkflow.Rendering
 import com.squareup.workflow1.ui.Screen
-import com.squareup.workflow1.ui.ViewEnvironment
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow1.ui.compose.ScreenComposableFactory
 import com.squareup.workflow1.ui.compose.WorkflowRendering
 import com.squareup.workflow1.ui.compose.tooling.Preview
 
 /**
- * Composition local of [Color] to use as the background color for a [RecursiveViewFactory].
+ * Composition local of [Color] to use as the background color for a [RecursiveComposableFactory].
  */
 val LocalBackgroundColor = compositionLocalOf<Color> { error("No background color specified") }
 
 /**
  * A `ViewFactory` that renders [RecursiveWorkflow.Rendering]s.
  */
 @OptIn(WorkflowUiExperimentalApi::class)
-val RecursiveViewFactory = ScreenComposableFactory<Rendering> { rendering, viewEnvironment ->
+val RecursiveComposableFactory = ScreenComposableFactory<Rendering> { rendering ->
   // Every child should be drawn with a slightly-darker background color.
   val color = LocalBackgroundColor.current
   val childColor = remember(color) {
@@ -57,7 +56,6 @@ val RecursiveViewFactory = ScreenComposableFactory<Rendering> { rendering, viewE
       CompositionLocalProvider(LocalBackgroundColor provides childColor) {
         Children(
           rendering.children,
-          viewEnvironment,
           // Pass a weight so that the column fills all the space not occupied by the buttons.
           modifier = Modifier.weight(1f, fill = true)
         )
@@ -75,7 +73,7 @@ val RecursiveViewFactory = ScreenComposableFactory<Rendering> { rendering, viewE
 @Composable
 fun RecursiveViewFactoryPreview() {
   CompositionLocalProvider(LocalBackgroundColor provides Color.Green) {
-    RecursiveViewFactory.Preview(
+    RecursiveComposableFactory.Preview(
       Rendering(
         children = listOf(
           StringRendering("foo"),
@@ -97,7 +95,6 @@ fun RecursiveViewFactoryPreview() {
 @Composable
 private fun Children(
   children: List<Screen>,
-  viewEnvironment: ViewEnvironment,
   modifier: Modifier
 ) {
   Column(
@@ -110,7 +107,6 @@ private fun Children(
         childRendering,
         // Pass a weight so all children are partitioned evenly within the total column space.
         // Without the weight, each child is the full size of the parent.
-        viewEnvironment,
         modifier = Modifier
           .weight(1f, fill = true)
           .fillMaxWidth()

samples/compose-samples/src/main/java/com/squareup/sample/compose/preview/PreviewActivity.kt

@@ -21,7 +21,6 @@ import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
 import com.squareup.workflow1.ui.Screen
-import com.squareup.workflow1.ui.ViewEnvironment
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow1.ui.compose.ComposeScreen
 import com.squareup.workflow1.ui.compose.WorkflowRendering
@@ -59,8 +58,8 @@ data class ContactRendering(
   val name: String,
   val details: ContactDetailsRendering
 ) : ComposeScreen {
-  @Composable override fun Content(viewEnvironment: ViewEnvironment) {
-    ContactDetails(this, viewEnvironment)
+  @Composable override fun Content() {
+    ContactDetails(this)
   }
 }
 
@@ -70,10 +69,7 @@ data class ContactDetailsRendering(
 ) : Screen
 
 @Composable
-private fun ContactDetails(
-  rendering: ContactRendering,
-  environment: ViewEnvironment
-) {
+private fun ContactDetails(rendering: ContactRendering) {
   Card(
     modifier = Modifier
       .padding(8.dp)
@@ -86,7 +82,6 @@ private fun ContactDetails(
       Text(rendering.name, style = MaterialTheme.typography.body1)
       WorkflowRendering(
         rendering = rendering.details,
-        viewEnvironment = environment,
         modifier = Modifier
           .aspectRatio(1f)
           .border(0.dp, Color.LightGray)

samples/compose-samples/src/main/java/com/squareup/sample/compose/textinput/App.kt

@@ -11,11 +11,11 @@ import com.squareup.workflow1.config.AndroidRuntimeConfigTools
 import com.squareup.workflow1.ui.ViewEnvironment
 import com.squareup.workflow1.ui.ViewRegistry
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
-import com.squareup.workflow1.ui.compose.WorkflowRendering
+import com.squareup.workflow1.ui.compose.RootScreen
 import com.squareup.workflow1.ui.compose.renderAsState
 import com.squareup.workflow1.ui.plus
 
-private val viewEnvironment = ViewEnvironment.EMPTY + ViewRegistry(TextInputViewFactory)
+private val viewEnvironment = ViewEnvironment.EMPTY + ViewRegistry(TextInputComposableFactory)
 
 @Composable fun TextInputApp() {
   MaterialTheme {
@@ -24,7 +24,7 @@ private val viewEnvironment = ViewEnvironment.EMPTY + ViewRegistry(TextInputView
       onOutput = {},
       runtimeConfig = AndroidRuntimeConfigTools.getAppWorkflowRuntimeConfig()
     )
-    WorkflowRendering(rendering, viewEnvironment)
+    viewEnvironment.RootScreen(rendering)
   }
 }
 

samples/compose-samples/src/main/java/com/squareup/sample/compose/textinput/TextInputViewFactory.kt

@@ -24,7 +24,7 @@ import com.squareup.workflow1.ui.compose.asMutableState
 import com.squareup.workflow1.ui.compose.tooling.Preview
 
 @OptIn(WorkflowUiExperimentalApi::class)
-val TextInputViewFactory = ScreenComposableFactory<Rendering> { rendering, _ ->
+val TextInputComposableFactory = ScreenComposableFactory<Rendering> { rendering ->
   Column(
     modifier = Modifier
       .fillMaxSize()
@@ -52,7 +52,7 @@ val TextInputViewFactory = ScreenComposableFactory<Rendering> { rendering, _ ->
 @Preview(showBackground = true)
 @Composable
 private fun TextInputViewFactoryPreview() {
-  TextInputViewFactory.Preview(
+  TextInputComposableFactory.Preview(
     Rendering(
       textController = TextController("Hello world"),
       onSwapText = {}

workflow-ui/compose-tooling/src/androidTest/java/com/squareup/workflow1/ui/compose/tooling/PreviewViewFactoryTest.kt

@@ -17,6 +17,7 @@ import androidx.test.ext.junit.runners.AndroidJUnit4
 import com.squareup.workflow1.ui.Screen
 import com.squareup.workflow1.ui.ViewEnvironmentKey
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
+import com.squareup.workflow1.ui.compose.LocalWorkflowEnvironment
 import com.squareup.workflow1.ui.compose.ScreenComposableFactory
 import com.squareup.workflow1.ui.compose.WorkflowRendering
 import com.squareup.workflow1.ui.internal.test.IdleAfterTestRule
@@ -96,10 +97,10 @@ internal class PreviewViewFactoryTest {
   }
 
   private val ParentWithOneChild =
-    ScreenComposableFactory<TwoStrings> { rendering, environment ->
+    ScreenComposableFactory<TwoStrings> { rendering ->
       Column {
         BasicText(rendering.first.text)
-        WorkflowRendering(rendering.second, environment)
+        WorkflowRendering(rendering.second)
       }
     }
 
@@ -109,11 +110,11 @@ internal class PreviewViewFactoryTest {
   }
 
   private val ParentWithTwoChildren =
-    ScreenComposableFactory<ThreeStrings> { rendering, environment ->
+    ScreenComposableFactory<ThreeStrings> { rendering ->
       Column {
-        WorkflowRendering(rendering.first, environment)
+        WorkflowRendering(rendering.first)
         BasicText(rendering.second.text)
-        WorkflowRendering(rendering.third, environment)
+        WorkflowRendering(rendering.third)
       }
     }
 
@@ -156,11 +157,11 @@ internal class PreviewViewFactoryTest {
   ) : Screen
 
   private val ParentRecursive =
-    ScreenComposableFactory<RecursiveRendering> { rendering, environment ->
+    ScreenComposableFactory<RecursiveRendering> { rendering ->
       Column {
         BasicText(rendering.text)
         rendering.child?.let { child ->
-          WorkflowRendering(rendering = child, viewEnvironment = environment)
+          WorkflowRendering(rendering = child)
         }
       }
     }
@@ -198,8 +199,8 @@ internal class PreviewViewFactoryTest {
     override val default: String get() = error("Not specified")
   }
 
-  private val ParentConsumesCustomKey = ScreenComposableFactory<TwoStrings> { _, environment ->
-    BasicText(environment[TestEnvironmentKey])
+  private val ParentConsumesCustomKey = ScreenComposableFactory<TwoStrings> { _ ->
+    BasicText(LocalWorkflowEnvironment.current[TestEnvironmentKey])
   }
 
   @Preview @Composable

workflow-ui/compose-tooling/src/main/java/com/squareup/workflow1/ui/compose/tooling/PlaceholderViewFactory.kt

@@ -34,7 +34,7 @@ import com.squareup.workflow1.ui.compose.ScreenComposableFactory
 internal fun placeholderScreenComposableFactory(
   modifier: Modifier
 ): ScreenComposableFactory<Screen> =
-  ScreenComposableFactory { rendering, _ ->
+  ScreenComposableFactory { rendering ->
     BoxWithConstraints {
       BasicText(
         modifier = modifier