Basic Litho support

Summary: Added an initial litho Tree observer and descriptors, its quiet naive and will be improved in a future diff

Reviewed By: lblasa

Differential Revision: D39466931

fbshipit-source-id: 66a462882af2e585b9719ee2f61595449f99c5e5

android/plugins/litho/build.gradle

@@ -6,6 +6,7 @@
  */
 
 apply plugin: 'com.android.library'
+apply plugin: 'kotlin-android'
 
 android {
     compileSdkVersion rootProject.compileSdkVersion

android/plugins/litho/src/main/java/com/facebook/flipper/plugins/uidebugger/litho/LithoDescriptors.kt

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.flipper.plugins.uidebugger.litho
+
+import com.facebook.flipper.plugins.uidebugger.common.InspectableObject
+import com.facebook.flipper.plugins.uidebugger.descriptors.Descriptor
+import com.facebook.litho.DebugComponent
+import com.facebook.litho.LithoView
+
+object LithoViewDescriptor : Descriptor<LithoView>() {
+  override fun getId(node: LithoView): String = System.identityHashCode(node).toString()
+
+  override fun getName(node: LithoView): String = "LithoView"
+
+  override fun getChildren(node: LithoView, children: MutableList<Any>) {
+    val debugComponent = DebugComponent.getRootInstance(node)
+    if (debugComponent != null) {
+      children.add(debugComponent)
+    }
+  }
+
+  override fun getActiveChild(node: LithoView): Any? = null
+
+  override fun getData(node: LithoView, builder: MutableMap<String, InspectableObject>) {}
+}
+
+object DebugComponentDescriptor : Descriptor<DebugComponent>() {
+  override fun getId(node: DebugComponent): String = System.identityHashCode(node).toString()
+
+  override fun getName(node: DebugComponent): String {
+    return node.component.simpleName
+  }
+
+  // TODO the mutable list thing doesnt make sense for non chained descriptors, should just return
+  override fun getChildren(node: DebugComponent, children: MutableList<Any>) {
+    val mountedView = node.mountedView
+    val mountedDrawable = node.mountedDrawable
+
+    if (mountedView != null) {
+      children.add(mountedView)
+    } else if (mountedDrawable != null) {
+      children.add(mountedDrawable)
+    } else {
+      for (child in node.childComponents) {
+        children.add(child)
+      }
+    }
+  }
+
+  override fun getActiveChild(node: DebugComponent): Any? = null
+
+  // todo same here
+  override fun getData(node: DebugComponent, builder: MutableMap<String, InspectableObject>) {}
+}

android/plugins/litho/src/main/java/com/facebook/flipper/plugins/uidebugger/litho/LithoObserver.kt

@@ -0,0 +1,53 @@
+package com.facebook.flipper.plugins.uidebugger.litho
+
+import com.facebook.flipper.plugins.uidebugger.SubtreeUpdate
+import com.facebook.flipper.plugins.uidebugger.TreeObserver
+import com.facebook.flipper.plugins.uidebugger.core.Context
+import com.facebook.flipper.plugins.uidebugger.identityHashCode
+import com.facebook.flipper.plugins.uidebugger.observers.TreeObserverBuilder
+import com.facebook.litho.LithoView
+
+class LithoViewTreeObserver(val context: Context) : TreeObserver<LithoView>() {
+
+  var nodeRef: LithoView? = null
+  override fun subscribe(node: Any) {
+    node as LithoView
+
+    nodeRef = node
+
+    val listener: (view: LithoView) -> Unit = {
+      val start = System.currentTimeMillis()
+
+      val (nodes, skipped) = context.layoutTraversal.traverse(it)
+
+      for (observerRoot in skipped) {
+        if (!children.containsKey(observerRoot.identityHashCode())) {
+          val observer = context.observerFactory.createObserver(observerRoot, context)!!
+          observer.subscribe(observerRoot)
+          children[observerRoot.identityHashCode()] = observer
+        }
+      }
+
+      context.treeObserverManager.emit(
+          SubtreeUpdate("Litho", nodes, start, System.currentTimeMillis()))
+    }
+    node.setOnDirtyMountListener(listener)
+
+    listener(node)
+  }
+
+  override fun unsubscribe() {
+    nodeRef?.setOnDirtyMountListener(null)
+    nodeRef = null
+  }
+}
+
+object LithoViewTreeObserverBuilder : TreeObserverBuilder<LithoView> {
+  override fun canBuildFor(node: Any): Boolean {
+    return node is LithoView
+  }
+
+  override fun build(context: Context): TreeObserver<LithoView> {
+    return LithoViewTreeObserver(context)
+  }
+}

android/plugins/litho/src/main/java/com/facebook/flipper/plugins/uidebugger/litho/UIDebuggerLithoSupport.kt

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.flipper.plugins.uidebugger.litho
+
+import com.facebook.flipper.plugins.uidebugger.descriptors.DescriptorRegister
+import com.facebook.flipper.plugins.uidebugger.observers.TreeObserverFactory
+import com.facebook.litho.DebugComponent
+import com.facebook.litho.LithoView
+
+object UIDebuggerLithoSupport {
+
+  fun addDescriptors(register: DescriptorRegister) {
+    register.register(LithoView::class.java, LithoViewDescriptor)
+    register.register(DebugComponent::class.java, DebugComponentDescriptor)
+  }
+
+  fun addObserver(observerFactory: TreeObserverFactory) {
+    observerFactory.register(LithoViewTreeObserverBuilder)
+  }
+}