Only call onLayout when layout has actually changed

Summary:
Developers are complaining about horrible lag (facebook#11809) caused by PR facebook#11222.

The issue was that hasNewLayout in yoga is actually a dirty bit and indicates that either you OR one of your children has a new layout. We still need to manually check whether the component's layout actually is different from before.

Reviewed By: sahrens

Differential Revision: D4597545

fbshipit-source-id: 27d4605afd00badfdcdacae740ee2e477adee929

ReactAndroid/src/androidTest/java/com/facebook/react/tests/LayoutEventsTestCase.java

@@ -28,8 +28,10 @@ protected String getReactApplicationKeyUnderTest() {
    * Creates a UI in JS and verifies the onLayout handler is called.
    */
   public void testOnLayoutCalled() {
-    assertEquals(1, mStringRecordingModule.getCalls().size());
+    assertEquals(3, mStringRecordingModule.getCalls().size());
     assertEquals("10,10-100x100", mStringRecordingModule.getCalls().get(0));
+    assertEquals("10,10-50x50", mStringRecordingModule.getCalls().get(1));
+    assertEquals("0,0-50x50", mStringRecordingModule.getCalls().get(2));
   }
 
   @Override

ReactAndroid/src/androidTest/js/LayoutEventsTestApp.js

@@ -16,18 +16,58 @@ var View = require('View');
 
 var RecordingModule = require('NativeModules').Recording;
 
+const LAYOUT_SPECS = [
+ [10, 10, 100, 100],
+ [10, 10, 50, 50],
+ [0, 0, 50, 50],
+ [0, 0, 50, 50],
+];
+
 class LayoutEventsTestApp extends React.Component {
+
+  constructor() {
+    super();
+    this.state = {
+      specNumber: 0,
+    };
+    this.numParentLayouts = 0;
+  }
+
   handleOnLayout = (e) => {
     var layout = e.nativeEvent.layout;
     RecordingModule.record(layout.x + ',' + layout.y + '-' + layout.width + 'x' + layout.height);
+
+    if (this.state.specNumber >= LAYOUT_SPECS.length) {
+      // This will cause the test to fail
+      RecordingModule.record('Got an extraneous layout call');
+    } else {
+      this.setState({
+        specNumber: this.state.specNumber + 1,
+      });
+    }
+  };
+
+  handleParentOnLayout = (e) => {
+    if (this.numParentLayouts > 0) {
+      // This will cause the test to fail - the parent's layout doesn't change
+      // so we should only get the event once.
+      RecordingModule.record('Got an extraneous layout call on the parent');
+    }
+    this.numParentLayouts++;
   };
 
   render() {
+    const layout = LAYOUT_SPECS[this.state.specNumber];
     return (
+      <View
+          onLayout={this.handleParentOnLayout}
+          testID="parent"
+          style={{left: 0, top: 0, width: 500, height: 500}}>
         <View
             onLayout={this.handleOnLayout}
             testID="container"
-            style={{left: 10, top: 10, width: 100, height: 100}}/>
+            style={{left: layout[0], top: layout[1], width: layout[2], height: layout[3]}}/>
+      </View>
     );
   }
 }

ReactAndroid/src/main/java/com/facebook/react/uimanager/ReactShadowNode.java

@@ -69,10 +69,10 @@ public class ReactShadowNode {
   private int mTotalNativeChildren = 0;
   private @Nullable ReactShadowNode mNativeParent;
   private @Nullable ArrayList<ReactShadowNode> mNativeChildren;
-  private float mAbsoluteLeft;
-  private float mAbsoluteTop;
-  private float mAbsoluteRight;
-  private float mAbsoluteBottom;
+  private int mScreenX;
+  private int mScreenY;
+  private int mScreenWidth;
+  private int mScreenHeight;
   private final Spacing mDefaultPadding = new Spacing(0);
   private final float[] mPadding = new float[Spacing.ALL + 1];
   private final boolean[] mPaddingIsPercent = new boolean[Spacing.ALL + 1];
@@ -292,12 +292,34 @@ public void onCollectExtraUpdates(UIViewOperationQueue uiViewOperationQueue) {
     }
 
     if (hasNewLayout()) {
-      mAbsoluteLeft = Math.round(absoluteX + getLayoutX());
-      mAbsoluteTop = Math.round(absoluteY + getLayoutY());
-      mAbsoluteRight = Math.round(absoluteX + getLayoutX() + getLayoutWidth());
-      mAbsoluteBottom = Math.round(absoluteY + getLayoutY() + getLayoutHeight());
-      nativeViewHierarchyOptimizer.handleUpdateLayout(this);
-      return true;
+      float layoutX = getLayoutX();
+      float layoutY = getLayoutY();
+      int newAbsoluteLeft = Math.round(absoluteX + layoutX);
+      int newAbsoluteTop = Math.round(absoluteY + layoutY);
+      int newAbsoluteRight = Math.round(absoluteX + layoutX + getLayoutWidth());
+      int newAbsoluteBottom = Math.round(absoluteY + layoutY + getLayoutHeight());
+
+      int newScreenX = Math.round(layoutX);
+      int newScreenY = Math.round(layoutY);
+      int newScreenWidth = newAbsoluteRight - newAbsoluteLeft;
+      int newScreenHeight = newAbsoluteBottom - newAbsoluteTop;
+
+      boolean layoutHasChanged =
+          newScreenX != mScreenX ||
+          newScreenY != mScreenY ||
+          newScreenWidth != mScreenWidth ||
+          newScreenHeight != mScreenHeight;
+
+      mScreenX = newScreenX;
+      mScreenY = newScreenY;
+      mScreenWidth = newScreenWidth;
+      mScreenHeight = newScreenHeight;
+
+      if (layoutHasChanged) {
+        nativeViewHierarchyOptimizer.handleUpdateLayout(this);
+      }
+
+      return layoutHasChanged;
     } else {
       return false;
     }
@@ -488,28 +510,28 @@ public final float getLayoutHeight() {
    * @return the x position of the corresponding view on the screen, rounded to pixels
    */
   public int getScreenX() {
-    return Math.round(getLayoutX());
+    return mScreenX;
   }
 
   /**
    * @return the y position of the corresponding view on the screen, rounded to pixels
    */
   public int getScreenY() {
-    return Math.round(getLayoutY());
+    return mScreenY;
   }
 
   /**
    * @return width corrected for rounding to pixels.
    */
   public int getScreenWidth() {
-    return Math.round(mAbsoluteRight - mAbsoluteLeft);
+    return mScreenWidth;
   }
 
   /**
    * @return height corrected for rounding to pixels.
    */
   public int getScreenHeight() {
-    return Math.round(mAbsoluteBottom - mAbsoluteTop);
+    return mScreenHeight;
   }
 
   public final YogaDirection getLayoutDirection() {