wip: ViewRegistry overhaul, ViewRendering, ModalRendering

Builds the simpler, more flexible scheme for modals proposed in #195. Only
AlertDialog takes advantage of it so far, and only the `hellobackbutton` and
`helloworkflow` samples are ported.

closes #195

 * We introduce the `ViewRendering` and `ModalRendering` interfaces,
   similar in sprit to `AnyScreen` in Swift.

 * `ViewRegistry` changes to be able to hold a collection of more arbitrary entry types, not just `ViewFactory`.
    * Its `buildView` method is deprecated.
    * Once we delete that method, we should be able to move `ViewRegistry` over to the
      non-Android, core UI module.

 * There are three implementations of `ViewRegistry.Entry`
    * Our old friend `ViewFactory<T: Any>`, now deprecated.
    * `ViewBuilder<T: ViewRendering>`, which replaces `ViewFactory`
    * `DialogBuilder<T: ModalRendering>`

 * Extension method `ViewRendering.buildView()` replaces `ViewRegistry.buildView()`. We also introduce  `ModalRendering.buildDialog()`.

    * These methods find the appropriate builder in `ViewRegistry`, based on the concrete type of the rendering, just like `ViewRegistry.buildView()` did.

    * The new ability of `ViewRegistry` to hold arbitrary entries means that we can add as many rendering:view-machinery pairings as we want to. Maybe cleans up Compose integration?

 * `LayoutRunner<T: Any>` is deprecated, replaced by `ViewRunner<T: ViewRendering>`. That's going to be a tedious migration for existing `LayoutRunner` implementations, but it avoids a huge breaking change —
 the new mechanism works in parallel with the deprecated one.

 * `WorkflowViewStub.display(rendering: ViewRendering)` replaces `WorkflowViewStub.update(rendering: Any)`, now deprecated. But the latter is able to delegate to the former so incremental migration is possible.

Author: rjrjr

samples/containers/android/src/main/java/com/squareup/sample/container/BackButtonViewFactory.kt renamed to samples/containers/android/src/main/java/com/squareup/sample/container/BackButtonViewBuilder.kt

@@ -1,17 +1,19 @@
 package com.squareup.sample.container
 
+import com.squareup.workflow1.ui.DecorativeViewBuilder
 import com.squareup.workflow1.ui.DecorativeViewFactory
+import com.squareup.workflow1.ui.ViewBuilder
 import com.squareup.workflow1.ui.ViewFactory
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow1.ui.backPressedHandler
 
 /**
- * [ViewFactory] that performs the work required by [BackButtonScreen].
+ * [ViewFactory] that performs the work required by [BackButtonViewRendering].
  */
 @WorkflowUiExperimentalApi
-object BackButtonViewFactory : ViewFactory<BackButtonScreen<*>>
-by DecorativeViewFactory(
-    type = BackButtonScreen::class,
+object BackButtonViewBuilder : ViewBuilder<BackButtonViewRendering<*>>
+by DecorativeViewBuilder(
+    type = BackButtonViewRendering::class,
     map = { outer -> outer.wrapped },
     doShowRendering = { view, innerShowRendering, outerRendering, viewEnvironment ->
       if (!outerRendering.override) {

samples/containers/android/src/main/java/com/squareup/sample/container/BackButtonScreen.kt renamed to samples/containers/android/src/main/java/com/squareup/sample/container/BackButtonViewRendering.kt

@@ -1,20 +1,6 @@
-/*
- * Copyright 2020 Square Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
 package com.squareup.sample.container
 
+import com.squareup.workflow1.ui.ViewRendering
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 
 /**
@@ -31,8 +17,8 @@ import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
  * is pressed, or null to set no handler. Defaults to `null`.
  */
 @WorkflowUiExperimentalApi
-data class BackButtonScreen<W : Any>(
+data class BackButtonViewRendering<W : ViewRendering>(
   val wrapped: W,
   val override: Boolean = false,
   val onBackPressed: (() -> Unit)? = null
-)
+) : ViewRendering

samples/containers/android/src/main/java/com/squareup/sample/container/SampleContainers.kt

@@ -23,5 +23,5 @@ import com.squareup.workflow1.ui.ViewRegistry
 
 @OptIn(WorkflowUiExperimentalApi::class)
 val SampleContainers = ViewRegistry(
-    BackButtonViewFactory, OverviewDetailContainer, PanelContainer, ScrimContainer
+    OverviewDetailContainer, PanelContainer, ScrimContainer
 )

samples/containers/android/src/main/java/com/squareup/sample/container/panel/ScrimContainer.kt

@@ -31,7 +31,7 @@ import com.squareup.workflow1.ui.bindShowRendering
  * A view that renders only its first child, behind a smoke scrim if
  * [isDimmed] is true (tablets only). Other children are ignored.
  *
- * Able to [render][com.squareup.workflow1.ui.showRendering] [ScrimContainerScreen].
+ * Able to [render][com.squareup.workflow1.ui.display] [ScrimContainerScreen].
  */
 class ScrimContainer @JvmOverloads constructor(
   context: Context,

samples/containers/hello-back-button/src/main/java/com/squareup/sample/hellobackbutton/AreYouSureWorkflow.kt

@@ -1,22 +1,7 @@
-/*
- * Copyright 2020 Square Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
 package com.squareup.sample.hellobackbutton
 
 import android.os.Parcelable
-import com.squareup.sample.container.BackButtonScreen
+import com.squareup.sample.container.BackButtonViewRendering
 import com.squareup.sample.hellobackbutton.AreYouSureWorkflow.Finished
 import com.squareup.sample.hellobackbutton.AreYouSureWorkflow.State
 import com.squareup.sample.hellobackbutton.AreYouSureWorkflow.State.Quitting
@@ -25,23 +10,27 @@ import com.squareup.workflow1.Snapshot
 import com.squareup.workflow1.StatefulWorkflow
 import com.squareup.workflow1.WorkflowAction.Companion.noAction
 import com.squareup.workflow1.action
+import com.squareup.workflow1.ui.AlertModalRendering
+import com.squareup.workflow1.ui.AlertModalRendering.Button.NEGATIVE
+import com.squareup.workflow1.ui.AlertModalRendering.Button.POSITIVE
+import com.squareup.workflow1.ui.AlertModalRendering.Event.ButtonClicked
+import com.squareup.workflow1.ui.AlertModalRendering.Event.Canceled
+import com.squareup.workflow1.ui.ModalContainerViewRendering
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
-import com.squareup.workflow1.ui.modal.AlertContainerScreen
-import com.squareup.workflow1.ui.modal.AlertScreen
-import com.squareup.workflow1.ui.modal.AlertScreen.Button.NEGATIVE
-import com.squareup.workflow1.ui.modal.AlertScreen.Button.POSITIVE
-import com.squareup.workflow1.ui.modal.AlertScreen.Event.ButtonClicked
-import com.squareup.workflow1.ui.modal.AlertScreen.Event.Canceled
 import com.squareup.workflow1.ui.toParcelable
 import com.squareup.workflow1.ui.toSnapshot
 import kotlinx.android.parcel.Parcelize
 
+@OptIn(WorkflowUiExperimentalApi::class)
+private typealias Rendering = ModalContainerViewRendering<*, AlertModalRendering>
+
 /**
  * Wraps [HelloBackButtonWorkflow] to (sometimes) pop a confirmation dialog when the back
  * button is pressed.
  */
 @OptIn(WorkflowUiExperimentalApi::class)
-object AreYouSureWorkflow : StatefulWorkflow<Unit, State, Finished, AlertContainerScreen<*>>() {
+object AreYouSureWorkflow :
+    StatefulWorkflow<Unit, State, Finished, Rendering>() {
   override fun initialState(
     props: Unit,
     snapshot: Snapshot?
@@ -59,13 +48,13 @@ object AreYouSureWorkflow : StatefulWorkflow<Unit, State, Finished, AlertContain
     props: Unit,
     state: State,
     context: RenderContext
-  ): AlertContainerScreen<*> {
+  ): Rendering {
     val ableBakerCharlie = context.renderChild(HelloBackButtonWorkflow, Unit) { noAction() }
 
     return when (state) {
       Running -> {
-        AlertContainerScreen(
-            BackButtonScreen(ableBakerCharlie) {
+        ModalContainerViewRendering(
+            BackButtonViewRendering(ableBakerCharlie) {
               // While we always provide a back button handler, by default the view code
               // associated with BackButtonScreen ignores ours if the view created for the
               // wrapped rendering sets a handler of its own. (Set BackButtonScreen.override
@@ -75,7 +64,7 @@ object AreYouSureWorkflow : StatefulWorkflow<Unit, State, Finished, AlertContain
         )
       }
       Quitting -> {
-        val dialog = AlertScreen(
+        val dialog = AlertModalRendering(
             buttons = mapOf(
                 POSITIVE to "I'm Positive",
                 NEGATIVE to "Negatory"
@@ -94,7 +83,7 @@ object AreYouSureWorkflow : StatefulWorkflow<Unit, State, Finished, AlertContain
             }
         )
 
-        AlertContainerScreen(ableBakerCharlie, dialog)
+        ModalContainerViewRendering(ableBakerCharlie, dialog)
       }
     }
   }

samples/containers/hello-back-button/src/main/java/com/squareup/sample/hellobackbutton/HelloBackButtonActivity.kt

@@ -17,18 +17,17 @@ package com.squareup.sample.hellobackbutton
 
 import android.os.Bundle
 import androidx.appcompat.app.AppCompatActivity
-import com.squareup.sample.container.SampleContainers
+import com.squareup.sample.container.BackButtonViewBuilder
 import com.squareup.workflow1.SimpleLoggingWorkflowInterceptor
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow1.ui.ViewRegistry
 import com.squareup.workflow1.ui.WorkflowRunner
-import com.squareup.workflow1.ui.modal.AlertContainer
 import com.squareup.workflow1.ui.plus
 import com.squareup.workflow1.ui.setContentWorkflow
 
 @OptIn(WorkflowUiExperimentalApi::class)
 private val viewRegistry =
-  ViewRegistry(HelloBackButtonLayoutRunner) + SampleContainers + AlertContainer
+  ViewRegistry(HelloBackButtonViewRunner) + BackButtonViewBuilder
 
 class HelloBackButtonActivity : AppCompatActivity() {
   @OptIn(WorkflowUiExperimentalApi::class)

samples/containers/hello-back-button/src/main/java/com/squareup/sample/hellobackbutton/HelloBackButtonLayoutRunner.kt

@@ -0,0 +1,31 @@
+package com.squareup.sample.hellobackbutton
+
+import android.view.View
+import android.widget.TextView
+import com.squareup.sample.hellobackbutton.HelloBackButtonWorkflow.Rendering
+import com.squareup.sample.hellobackbutton.R.id
+import com.squareup.sample.hellobackbutton.R.layout
+import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
+import com.squareup.workflow1.ui.ViewBuilder
+import com.squareup.workflow1.ui.ViewEnvironment
+import com.squareup.workflow1.ui.ViewRunner
+import com.squareup.workflow1.ui.ViewRunner.Companion.bind
+import com.squareup.workflow1.ui.backPressedHandler
+
+@OptIn(WorkflowUiExperimentalApi::class)
+internal class HelloBackButtonViewRunner(view: View) : ViewRunner<Rendering> {
+  private val messageView: TextView = view.findViewById(id.hello_message)
+
+  override fun showRendering(
+    rendering: Rendering,
+    viewEnvironment: ViewEnvironment
+  ) {
+    messageView.text = rendering.message
+    messageView.setOnClickListener { rendering.onClick() }
+    messageView.backPressedHandler = rendering.onBackPressed
+  }
+
+  companion object : ViewBuilder<Rendering> by bind(
+      layout.hello_back_button_layout, ::HelloBackButtonViewRunner
+  )
+}

samples/containers/hello-back-button/src/main/java/com/squareup/sample/hellobackbutton/HelloBackButtonViewRunner.kt

@@ -16,31 +16,33 @@
 package com.squareup.sample.hellobackbutton
 
 import android.os.Parcelable
-import com.squareup.sample.hellobackbutton.HelloBackButtonWorkflow.Rendering
 import com.squareup.sample.hellobackbutton.HelloBackButtonWorkflow.State
 import com.squareup.sample.hellobackbutton.HelloBackButtonWorkflow.State.Able
 import com.squareup.sample.hellobackbutton.HelloBackButtonWorkflow.State.Baker
 import com.squareup.sample.hellobackbutton.HelloBackButtonWorkflow.State.Charlie
 import com.squareup.workflow1.Snapshot
 import com.squareup.workflow1.StatefulWorkflow
 import com.squareup.workflow1.action
+import com.squareup.workflow1.ui.ViewRendering
+import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow1.ui.toParcelable
 import com.squareup.workflow1.ui.toSnapshot
 import kotlinx.android.parcel.Parcelize
 
-object HelloBackButtonWorkflow : StatefulWorkflow<Unit, State, Nothing, Rendering>() {
+@OptIn(WorkflowUiExperimentalApi::class)
+object HelloBackButtonWorkflow : StatefulWorkflow<Unit, State, Nothing, ViewRendering>() {
   @Parcelize
   enum class State : Parcelable {
     Able,
     Baker,
     Charlie;
   }
 
-  data class Rendering(
+  internal data class Rendering(
     val message: String,
     val onClick: () -> Unit,
     val onBackPressed: (() -> Unit)?
-  )
+  ) : ViewRendering
 
   override fun initialState(
     props: Unit,
@@ -51,7 +53,7 @@ object HelloBackButtonWorkflow : StatefulWorkflow<Unit, State, Nothing, Renderin
     props: Unit,
     state: State,
     context: RenderContext
-  ): Rendering {
+  ): ViewRendering {
     return Rendering(
         message = "$state",
         onClick = { context.actionSink.send(advance) },

samples/containers/hello-back-button/src/main/java/com/squareup/sample/hellobackbutton/HelloBackButtonWorkflow.kt

@@ -19,11 +19,13 @@ import com.squareup.sample.helloworkflow.HelloWorkflow.Rendering
 import com.squareup.sample.helloworkflow.databinding.HelloGoodbyeLayoutBinding
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow1.ui.LayoutRunner
+import com.squareup.workflow1.ui.ViewBuilder
 import com.squareup.workflow1.ui.ViewFactory
+import com.squareup.workflow1.ui.ViewRunner
 
 @OptIn(WorkflowUiExperimentalApi::class)
-val HelloViewFactory: ViewFactory<Rendering> =
-  LayoutRunner.bind(HelloGoodbyeLayoutBinding::inflate) { rendering, _ ->
+val HelloViewBuilder: ViewBuilder<Rendering> =
+  ViewRunner.bind(HelloGoodbyeLayoutBinding::inflate) { rendering, _ ->
     helloMessage.text = rendering.message
     helloMessage.setOnClickListener { rendering.onClick() }
   }