Optimize pre-allocation of views

Summary: This diff changes the way pre-allocation of views are executed in Fabric. Before this diff the execution of view preallocation was schedulled at the end of the UIThread queue, now the views are pre-allocated in the next "tick"

Reviewed By: sahrens

Differential Revision: D13857614

fbshipit-source-id: 386bf966d3c8a0d5c0bd626119a92810465aecb7

ReactAndroid/src/main/java/com/facebook/react/fabric/FabricUIManager.java

@@ -29,6 +29,7 @@
 import com.facebook.react.fabric.mounting.mountitems.DispatchCommandMountItem;
 import com.facebook.react.fabric.mounting.mountitems.InsertMountItem;
 import com.facebook.react.fabric.mounting.mountitems.MountItem;
+import com.facebook.react.fabric.mounting.mountitems.PreAllocateViewMountItem;
 import com.facebook.react.fabric.mounting.mountitems.RemoveMountItem;
 import com.facebook.react.fabric.mounting.mountitems.UpdateEventEmitterMountItem;
 import com.facebook.react.fabric.mounting.mountitems.UpdateLayoutMountItem;
@@ -49,6 +50,7 @@
 import com.facebook.react.bridge.WritableMap;
 import com.facebook.react.common.ReactConstants;
 import com.facebook.react.modules.core.ReactChoreographer;
+import com.facebook.react.uimanager.IllegalViewOperationException;
 import com.facebook.react.uimanager.ReactRootViewTagGenerator;
 import com.facebook.react.uimanager.ThemedReactContext;
 import com.facebook.react.uimanager.ViewManagerPropertyUpdater;
@@ -94,10 +96,14 @@ public class FabricUIManager implements UIManager, LifecycleEventListener {
       new ConcurrentHashMap<>();
   private final EventBeatManager mEventBeatManager;
   private final Object mMountItemsLock = new Object();
+  private final Object mPreMountItemsLock = new Object();
 
   @GuardedBy("mMountItemsLock")
   private List<MountItem> mMountItems = new ArrayList<>();
 
+  @GuardedBy("mPreMountItemsLock")
+  private List<MountItem> mPreMountItems = new ArrayList<>();
+
   @ThreadConfined(UI)
   private final DispatchUIFrameCallback mDispatchUIFrameCallback;
 
@@ -177,17 +183,13 @@ public void onCatalystInstanceDestroy() {
 
   @DoNotStrip
   private void preallocateView(final int rootTag, final String componentName) {
-    UiThreadUtil.runOnUiThread(
-        new GuardedRunnable(mReactApplicationContext) {
-          @Override
-          public void runGuarded() {
-            ThemedReactContext context =
-                Assertions.assertNotNull(mReactContextForRootTag.get(rootTag));
-            String component = sComponentNames.get(componentName);
-            Assertions.assertNotNull(component);
-            mMountingManager.preallocateView(context, component);
-          }
-        });
+    synchronized (mPreMountItemsLock) {
+      ThemedReactContext context =
+        Assertions.assertNotNull(mReactContextForRootTag.get(rootTag));
+      String component = sComponentNames.get(componentName);
+      Assertions.assertNotNull(component);
+      mPreMountItems.add(new PreAllocateViewMountItem(context, rootTag, component));
+    }
   }
 
   @DoNotStrip
@@ -286,25 +288,35 @@ private void flushMountItems() {
     }
 
     try {
+      List<MountItem> preMountItemsToDispatch;
+      synchronized (mPreMountItemsLock) {
+        preMountItemsToDispatch = mPreMountItems;
+        mPreMountItems = new ArrayList<>();
+      }
+
       List<MountItem> mountItemsToDispatch;
       synchronized (mMountItemsLock) {
-        if (mMountItems.isEmpty()) {
-          return;
-        }
         mountItemsToDispatch = mMountItems;
         mMountItems = new ArrayList<>();
       }
 
+      Systrace.beginSection(
+        Systrace.TRACE_TAG_REACT_JAVA_BRIDGE,
+        "FabricUIManager::premountViews (" + preMountItemsToDispatch.size() + " batches)");
+      for (MountItem mountItem : preMountItemsToDispatch) {
+        mountItem.execute(mMountingManager);
+      }
+      Systrace.endSection(Systrace.TRACE_TAG_REACT_JAVA_BRIDGE);
+
       Systrace.beginSection(
           Systrace.TRACE_TAG_REACT_JAVA_BRIDGE,
           "FabricUIManager::mountViews (" + mountItemsToDispatch.size() + " batches)");
       for (MountItem mountItem : mountItemsToDispatch) {
         mountItem.execute(mMountingManager);
       }
-
       Systrace.endSection(Systrace.TRACE_TAG_REACT_JAVA_BRIDGE);
     } catch (Exception ex) {
-      FLog.i(ReactConstants.TAG, "Exception thrown when executing UIFrameGuarded", ex);
+      FLog.e(ReactConstants.TAG, "Exception thrown when executing UIFrameGuarded", ex);
       mIsMountingEnabled = false;
       throw ex;
     }

ReactAndroid/src/main/java/com/facebook/react/fabric/mounting/mountitems/BatchMountItem.java

@@ -6,8 +6,8 @@
  */
 package com.facebook.react.fabric.mounting.mountitems;
 
-import com.facebook.react.fabric.mounting.MountingManager;
 import com.facebook.proguard.annotations.DoNotStrip;
+import com.facebook.react.fabric.mounting.MountingManager;
 import com.facebook.systrace.Systrace;
 
 /**

ReactAndroid/src/main/java/com/facebook/react/fabric/mounting/mountitems/PreAllocateViewMountItem.java

@@ -0,0 +1,36 @@
+/**
+ * Copyright (c) Facebook, Inc. and its 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.react.fabric.mounting.mountitems;
+
+import com.facebook.react.fabric.mounting.MountingManager;
+import com.facebook.react.uimanager.ThemedReactContext;
+
+/**
+ * {@link MountItem} that is used to pre-allocate views for JS components.
+ */
+public class PreAllocateViewMountItem implements MountItem {
+
+  private final String mComponent;
+  private final int mRootTag;
+  private final ThemedReactContext mContext;
+
+  public PreAllocateViewMountItem(ThemedReactContext context, int rootTag, String component){
+    mContext = context;
+    mComponent = component;
+    mRootTag = rootTag;
+  }
+
+  @Override
+  public void execute(MountingManager mountingManager) {
+    mountingManager.preallocateView(mContext, mComponent);
+  }
+
+  @Override
+  public String toString() {
+    return "[" + mRootTag + "] - Preallocate " + mComponent;
+  }
+}