From c929e15523c2c33297b1e9895e9bea49442e4f73 Mon Sep 17 00:00:00 2001
From: Dave Miller <dmmiller@fb.com>
Date: Mon, 30 Nov 2015 05:24:13 -0800
Subject: [PATCH] Update touch handling to properly handle transformed Views

Summary: public

Our view handling for determining if a touch was in a view was not transform aware.  This updates it to be
transform aware (by borrowing the code from ViewGroup).

Now, touches will be correctly translated to the view if the view is transformed.  They will also have the correct
local touch point.

This fixes https://github.com/facebook/react-native/issues/3557

Reviewed By: andreicoman11

Differential Revision: D2696063

fb-gh-sync-id: 291f6b9884c610c29f8f8b9992c98d59863ab481
---
 .../react/uimanager/TouchTargetHelper.java    | 60 +++++++++++++++----
 1 file changed, 47 insertions(+), 13 deletions(-)

diff --git a/ReactAndroid/src/main/java/com/facebook/react/uimanager/TouchTargetHelper.java b/ReactAndroid/src/main/java/com/facebook/react/uimanager/TouchTargetHelper.java
index 409a9f91f..24a4d2869 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/uimanager/TouchTargetHelper.java
+++ b/ReactAndroid/src/main/java/com/facebook/react/uimanager/TouchTargetHelper.java
@@ -11,6 +11,8 @@ package com.facebook.react.uimanager;
 
 import javax.annotation.Nullable;
 
+import android.graphics.Matrix;
+import android.graphics.PointF;
 import android.view.MotionEvent;
 import android.view.View;
 import android.view.ViewGroup;
@@ -25,6 +27,9 @@ import com.facebook.react.bridge.UiThreadUtil;
 public class TouchTargetHelper {
 
   private static final float[] mEventCoords = new float[2];
+  private static final PointF mTempPoint = new PointF();
+  private static final float[] mMatrixTransformCoords = new float[2];
+  private static final Matrix mInverseMatrix = new Matrix();
 
   /**
    * Find touch event target view within the provided container given the coordinates provided
@@ -94,31 +99,60 @@ public class TouchTargetHelper {
     int childrenCount = viewGroup.getChildCount();
     for (int i = childrenCount - 1; i >= 0; i--) {
       View child = viewGroup.getChildAt(i);
-      if (isTouchPointInView(eventCoords[0], eventCoords[1], viewGroup, child)) {
-        // Apply offset to event coordinates to transform them into the coordinate space of the
-        // child view, taken from {@link ViewGroup#dispatchTransformedTouchEvent()}.
-        eventCoords[0] += viewGroup.getScrollY() - child.getTop();
-        eventCoords[1] += viewGroup.getScrollX() - child.getLeft();
+      PointF childPoint = mTempPoint;
+      if (isTransformedTouchPointInView(eventCoords[0], eventCoords[1], viewGroup, child, childPoint)) {
+        // If it is contained within the child View, the childPoint value will contain the view
+        // coordinates relative to the child
+        // We need to store the existing X,Y for the viewGroup away as it is possible this child
+        // will not actually be the target and so we restore them if not
+        float restoreY = eventCoords[0];
+        float restoreX = eventCoords[1];
+        eventCoords[0] = childPoint.y;
+        eventCoords[1] = childPoint.x;
         View targetView = findTouchTargetViewWithPointerEvents(eventCoords, child);
         if (targetView != null) {
           return targetView;
         }
-        eventCoords[0] -= viewGroup.getScrollY() - child.getTop();
-        eventCoords[1] -= viewGroup.getScrollX() - child.getLeft();
+        eventCoords[0] = restoreY;
+        eventCoords[1] = restoreX;
       }
     }
     return viewGroup;
 }
 
-  // Taken from {@link ViewGroup#isTransformedTouchPointInView()}
-  private static boolean isTouchPointInView(float y, float x, ViewGroup parent, View child) {
-    float localY = y + parent.getScrollY() - child.getTop();
+  /**
+   * Returns whether the touch point is within the child View
+   * It is transform aware and will invert the transform Matrix to find the true local points
+   * This code is taken from {@link ViewGroup#isTransformedTouchPointInView()}
+   */
+  private static boolean isTransformedTouchPointInView(
+      float y,
+      float x,
+      ViewGroup parent,
+      View child,
+      PointF outLocalPoint) {
     float localX = x + parent.getScrollX() - child.getLeft();
-    // Taken from {@link View#pointInView()}.
-    return localY >= 0 && localY < (child.getBottom() - child.getTop())
-        && localX >= 0 && localX < (child.getRight() - child.getLeft());
+    float localY = y + parent.getScrollY() - child.getTop();
+    Matrix matrix = child.getMatrix();
+    if (!matrix.isIdentity()) {
+      float[] localXY = mMatrixTransformCoords;
+      localXY[0] = localX;
+      localXY[1] = localY;
+      Matrix inverseMatrix = mInverseMatrix;
+      matrix.invert(inverseMatrix);
+      inverseMatrix.mapPoints(localXY);
+      localX = localXY[0];
+      localY = localXY[1];
+    }
+    if ((localX >= 0 && localX < (child.getRight() - child.getLeft()))
+        && (localY >= 0 && localY < (child.getBottom() - child.getTop()))) {
+      outLocalPoint.set(localX, localY);
+      return true;
+    }
+    return false;
   }
 
+
   /**
    * Returns the touch target View of the event given, or null if neither the given View nor any of
    * its descendants are the touch target.