From e3d8e632e86016d3a5cc7baf8e75b090f4a3aaad Mon Sep 17 00:00:00 2001
From: Satyajit Sahoo <satyajit.happy@gmail.com>
Date: Sat, 4 Feb 2017 11:05:37 -0800
Subject: [PATCH] Add perspective transform support on Android

Summary:
Rebased #6926 against master.

Fixes #2915
Closes https://github.com/facebook/react-native/pull/11713

Differential Revision: D4513111

fbshipit-source-id: 9fb653c4bfd64eda12a605f6cabb0159b2af8f73
---
 Examples/UIExplorer/js/TransformExample.js    |  2 +-
 .../react/uimanager/BaseViewManager.java      | 22 +++++++++++++++++--
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/Examples/UIExplorer/js/TransformExample.js b/Examples/UIExplorer/js/TransformExample.js
index ea7ad3d156703f..f6d028566113b3 100644
--- a/Examples/UIExplorer/js/TransformExample.js
+++ b/Examples/UIExplorer/js/TransformExample.js
@@ -211,7 +211,7 @@ exports.title = 'Transforms';
 exports.description = 'View transforms';
 exports.examples = [
   {
-    title: 'Perspective',
+    title: 'Perspective, Rotate, Animation',
     description: 'perspective: 850, rotateX: Animated.timing(0 -> 360)',
     render(): React.Element<any> { return <Flip />; }
   },
diff --git a/ReactAndroid/src/main/java/com/facebook/react/uimanager/BaseViewManager.java b/ReactAndroid/src/main/java/com/facebook/react/uimanager/BaseViewManager.java
index 815bad0faddcc5..24192175df1232 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/uimanager/BaseViewManager.java
+++ b/ReactAndroid/src/main/java/com/facebook/react/uimanager/BaseViewManager.java
@@ -5,8 +5,6 @@
 import android.graphics.Color;
 import android.os.Build;
 import android.view.View;
-import android.view.ViewGroup;
-
 import com.facebook.react.bridge.ReadableArray;
 import com.facebook.react.uimanager.annotations.ReactProp;
 
@@ -35,6 +33,9 @@ public abstract class BaseViewManager<T extends View, C extends LayoutShadowNode
   private static final String PROP_TRANSLATE_X = "translateX";
   private static final String PROP_TRANSLATE_Y = "translateY";
 
+  private static final int PERSPECTIVE_ARRAY_INVERTED_CAMERA_DISTANCE_INDEX = 2;
+  private static final float CAMERA_DISTANCE_NORMALIZATION_MULTIPLIER = 5;
+
   /**
    * Used to locate views in end-to-end (UI) tests.
    */
@@ -165,6 +166,22 @@ private static void setTransformProperty(View view, ReadableArray transforms) {
     view.setRotationY((float) sMatrixDecompositionContext.rotationDegrees[1]);
     view.setScaleX((float) sMatrixDecompositionContext.scale[0]);
     view.setScaleY((float) sMatrixDecompositionContext.scale[1]);
+
+    double[] perspectiveArray = sMatrixDecompositionContext.perspective;
+
+    if (perspectiveArray.length > PERSPECTIVE_ARRAY_INVERTED_CAMERA_DISTANCE_INDEX) {
+      float invertedCameraDistance = (float) perspectiveArray[PERSPECTIVE_ARRAY_INVERTED_CAMERA_DISTANCE_INDEX];
+      if (invertedCameraDistance < 0) {
+        float cameraDistance = -1 / invertedCameraDistance;
+        float scale = DisplayMetricsHolder.getScreenDisplayMetrics().density;
+
+        // The following converts the matrix's perspective to a camera distance
+        // such that the camera perspective looks the same on Android and iOS
+        float normalizedCameraDistance = scale * cameraDistance * CAMERA_DISTANCE_NORMALIZATION_MULTIPLIER;
+
+        view.setCameraDistance(normalizedCameraDistance);
+      }
+    }
   }
 
   private static void resetTransformProperty(View view) {
@@ -175,5 +192,6 @@ private static void resetTransformProperty(View view) {
     view.setRotationY(0);
     view.setScaleX(1);
     view.setScaleY(1);
+    view.setCameraDistance(0);
   }
 }