Extracted snapshot out of descriptor

Summary: Snapshot never made much sense in the descriptor since we only snapshot the decor views. Additionally in the next diff i will introduce a new way to snapshot so this will make it easier

Reviewed By: lblasa

Differential Revision: D50845280

fbshipit-source-id: c2eac351b72786e7b66951d0fa09cea52a6dcc69

android/src/main/java/com/facebook/flipper/plugins/uidebugger/common/BitmapPool.kt

@@ -16,7 +16,7 @@ import kotlinx.coroutines.launch
 class BitmapPool(private val config: Bitmap.Config = Bitmap.Config.RGB_565) {
 
   interface ReusableBitmap {
-    val bitmap: Bitmap?
+    val bitmap: Bitmap
 
     fun readyForReuse()
   }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/core/DecorViewTracker.kt

@@ -11,7 +11,6 @@ import android.util.Log
 import android.view.View
 import android.view.ViewTreeObserver
 import com.facebook.flipper.plugins.uidebugger.LogTag
-import com.facebook.flipper.plugins.uidebugger.common.BitmapPool
 import com.facebook.flipper.plugins.uidebugger.descriptors.ViewDescriptor
 import com.facebook.flipper.plugins.uidebugger.util.StopWatch
 import com.facebook.flipper.plugins.uidebugger.util.Throttler
@@ -22,7 +21,7 @@ import com.facebook.flipper.plugins.uidebugger.util.objectIdentity
  * to it This predraw observer triggers a full traversal of the UI. There should only ever be one
  * active predraw listener at once
  */
-class DecorViewTracker(val context: UIDContext) {
+class DecorViewTracker(private val context: UIDContext, private val snapshotter: Snapshotter) {
 
   private var currentDecorView: View? = null
   private var preDrawListener: ViewTreeObserver.OnPreDrawListener? = null
@@ -88,18 +87,7 @@ class DecorViewTracker(val context: UIDContext) {
     val (nodes, traversalTime) =
         StopWatch.time { context.layoutTraversal.traverse(context.applicationRef) }
 
-    mStopWatch.start()
-    var snapshotBitmap: BitmapPool.ReusableBitmap? = null
-    if (decorView.width > 0 && decorView.height > 0) {
-      snapshotBitmap = context.bitmapPool.getBitmap(decorView.width, decorView.height)
-      context.bitmapPool.getBitmap(decorView.width, decorView.height)
-      Log.i(
-          LogTag,
-          "Snapshotting view ${ViewDescriptor.getId(decorView)}",
-      )
-      ViewDescriptor.getSnapshot(decorView, snapshotBitmap.bitmap)
-    }
-    val snapshotTime = mStopWatch.stop()
+    val (reusableBitmap, snapshotMs) = StopWatch.time { snapshotter.takeSnapshot(decorView) }
 
     context.updateQueue.enqueueUpdate(
         Update(
@@ -107,8 +95,8 @@ class DecorViewTracker(val context: UIDContext) {
             nodes,
             startTimestamp,
             traversalTime,
-            snapshotTime,
+            snapshotMs,
             System.currentTimeMillis(),
-            snapshotBitmap))
+            reusableBitmap))
   }
 }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/core/Snapshot.kt

@@ -0,0 +1,43 @@
+/*
+ * 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.core
+
+import android.graphics.Canvas
+import android.util.Log
+import android.view.View
+import com.facebook.flipper.plugins.uidebugger.LogTag
+import com.facebook.flipper.plugins.uidebugger.common.BitmapPool
+
+interface Snapshotter {
+  fun takeSnapshot(view: View): BitmapPool.ReusableBitmap?
+}
+
+/**
+ * Takes a snapshot by redrawing the view into a bitmap backed canvas, Since this is software
+ * rendering there can be discrepancies between the real image and the snapshot:
+ * 1. It can be unreliable when snapshotting views that are added directly to window manager
+ * 2. It doesnt include certain types of content (video / images)
+ */
+class CanvasSnapshotter(private val bitmapPool: BitmapPool) : Snapshotter {
+  override fun takeSnapshot(view: View): BitmapPool.ReusableBitmap? {
+
+    if (view.width <= 0 || view.height <= 0) {
+      return null
+    }
+
+    return try {
+      val reuseAbleBitmap = bitmapPool.getBitmap(view.width, view.height)
+      val canvas = Canvas(reuseAbleBitmap.bitmap)
+      view.draw(canvas)
+      reuseAbleBitmap
+    } catch (e: OutOfMemoryError) {
+      Log.e(LogTag, "OOM when taking snapshot")
+      null
+    }
+  }
+}

android/src/main/java/com/facebook/flipper/plugins/uidebugger/core/UIDContext.kt

@@ -31,12 +31,11 @@ class UIDContext(
     private val pendingFrameworkEvents: MutableList<FrameworkEvent>
 ) {
 
-  val decorViewTracker = DecorViewTracker(this)
+  val bitmapPool = BitmapPool()
+  val decorViewTracker = DecorViewTracker(this, CanvasSnapshotter(bitmapPool))
   val updateQueue = UpdateQueue(this)
   val layoutTraversal: LayoutTraversal = LayoutTraversal(this)
 
-  val bitmapPool = BitmapPool()
-
   fun addFrameworkEvent(frameworkEvent: FrameworkEvent) {
     synchronized(pendingFrameworkEvents) { pendingFrameworkEvents.add(frameworkEvent) }
   }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/ChainedDescriptor.kt

@@ -7,7 +7,6 @@
 
 package com.facebook.flipper.plugins.uidebugger.descriptors
 
-import android.graphics.Bitmap
 import com.facebook.flipper.plugins.uidebugger.model.Bounds
 import com.facebook.flipper.plugins.uidebugger.model.InspectableObject
 import com.facebook.flipper.plugins.uidebugger.model.MetadataId
@@ -133,15 +132,6 @@ abstract class ChainedDescriptor<T> : NodeDescriptor<T> {
    */
   open fun onGetAttributes(node: T, attributeSections: MutableMap<MetadataId, InspectableObject>) {}
 
-  /** Get a snapshot of the node. */
-  final override fun getSnapshot(node: T, bitmap: Bitmap?): Bitmap? {
-    return onGetSnapshot(node, bitmap) ?: mSuper?.onGetSnapshot(node, bitmap)
-  }
-
-  open fun onGetSnapshot(node: T, bitmap: Bitmap?): Bitmap? {
-    return null
-  }
-
   final override fun getInlineAttributes(node: T): Map<String, String> {
 
     val builder = mutableMapOf<String, String>()

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/NodeDescriptor.kt

@@ -7,7 +7,6 @@
 
 package com.facebook.flipper.plugins.uidebugger.descriptors
 
-import android.graphics.Bitmap
 import com.facebook.flipper.plugins.uidebugger.model.Bounds
 import com.facebook.flipper.plugins.uidebugger.model.InspectableObject
 import com.facebook.flipper.plugins.uidebugger.model.MetadataId
@@ -58,13 +57,6 @@ interface NodeDescriptor<T> {
   /** The children this node exposes in the inspector. */
   fun getChildren(node: T): List<Any>
 
-  /**
-   * Get a snapshot of the node. Bitmaps are not cheap to create, so accept one as an optional
-   * parameter. If a bitmap is provided, it will be used by the canvas to draw on it. Otherwise, a
-   * bitmap will be created.
-   */
-  fun getSnapshot(node: T, bitmap: Bitmap?): Bitmap? = null
-
   /**
    * If you have overlapping children this indicates which child is active / on top, we will only
    * listen to / traverse this child. If return null we assume all children are 'active'

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/ObjectDescriptor.kt

@@ -7,7 +7,6 @@
 
 package com.facebook.flipper.plugins.uidebugger.descriptors
 
-import android.graphics.Bitmap
 import com.facebook.flipper.plugins.uidebugger.model.Bounds
 import com.facebook.flipper.plugins.uidebugger.model.InspectableObject
 import com.facebook.flipper.plugins.uidebugger.model.MetadataId
@@ -34,6 +33,4 @@ object ObjectDescriptor : NodeDescriptor<Any> {
   override fun getBounds(node: Any): Bounds = Bounds(0, 0, 0, 0)
 
   override fun getTags(node: Any): Set<String> = setOf(BaseTags.Unknown)
-
-  override fun getSnapshot(node: Any, bitmap: Bitmap?): Bitmap? = null
 }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/OffsetChildDescriptor.kt

@@ -7,7 +7,6 @@
 
 package com.facebook.flipper.plugins.uidebugger.descriptors
 
-import android.graphics.Bitmap
 import com.facebook.flipper.plugins.uidebugger.model.Bounds
 import com.facebook.flipper.plugins.uidebugger.model.InspectableObject
 import com.facebook.flipper.plugins.uidebugger.model.MetadataId
@@ -42,7 +41,4 @@ object OffsetChildDescriptor : NodeDescriptor<OffsetChild> {
       node.descriptor.getAttributes(node.child)
 
   override fun getTags(node: OffsetChild): Set<String> = node.descriptor.getTags(node.child)
-
-  override fun getSnapshot(node: OffsetChild, bitmap: Bitmap?): Bitmap? =
-      node.descriptor.getSnapshot(node.child, bitmap)
 }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/ViewDescriptor.kt

@@ -8,8 +8,6 @@
 package com.facebook.flipper.plugins.uidebugger.descriptors
 
 import android.annotation.SuppressLint
-import android.graphics.Bitmap
-import android.graphics.Canvas
 import android.graphics.Rect
 import android.graphics.drawable.ColorDrawable
 import android.graphics.drawable.Drawable
@@ -380,30 +378,6 @@ object ViewDescriptor : ChainedDescriptor<View>() {
     attributes["id"] = value
   }
 
-  override fun onGetSnapshot(node: View, bitmap: Bitmap?): Bitmap? {
-    if (node.width <= 0 || node.height <= 0) {
-      return null
-    }
-    var workingBitmap = bitmap
-
-    try {
-      val differentSize =
-          if (bitmap != null) (node.width != bitmap.width || node.height != bitmap.height)
-          else false
-      if (workingBitmap == null || differentSize) {
-        val viewWidth: Int = node.width
-        val viewHeight: Int = node.height
-
-        workingBitmap = BitmapPool.createBitmapWithDefaultConfig(viewWidth, viewHeight)
-      }
-
-      val canvas = Canvas(workingBitmap)
-      node.draw(canvas)
-    } catch (e: OutOfMemoryError) {}
-
-    return workingBitmap
-  }
-
   private fun fromDrawable(d: Drawable?): Inspectable? {
     return if (d is ColorDrawable) {
       InspectableValue.Color(Color.fromColor(d.color))