From 3e760f48c5a28b592cb60c4060ca28a1574f6274 Mon Sep 17 00:00:00 2001
From: Kevin Stumpf <kevin@dispatchertrucking.com>
Date: Tue, 15 Mar 2016 11:51:31 -0700
Subject: [PATCH] Android support for perspective transform

Summary:- Motivation: ["Perspective" Transform](https://facebook.github.io/react-native/docs/transforms.html#proptypes) was so far supported only on iOS
- Closes #2915
- Test Plan: I built a [react-native-flip-view](https://github.com/DispatcherInc/react-native-flip-view) and ensured that the same perspective transform results in the same camera perspective on both iOS and Android:

![image](https://cloud.githubusercontent.com/assets/7293984/13342624/6556cfe0-dbf8-11e5-8fb2-05554a5081b7.png)

![image](https://cloud.githubusercontent.com/assets/7293984/13342677/daf90560-dbf8-11e5-9941-2ae0f9f9d99b.png)
Closes https://github.com/facebook/react-native/pull/6159

Differential Revision: D3053532

Pulled By: mkonicek

fb-gh-sync-id: a39a9fbafe0fc7c648fdafc2eb69f651fe58d9fb
shipit-source-id: a39a9fbafe0fc7c648fdafc2eb69f651fe58d9fb
---
 .../react/uimanager/BaseViewManager.java      | 21 ++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

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 9a697ce3a..12fbae977 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/uimanager/BaseViewManager.java
+++ b/ReactAndroid/src/main/java/com/facebook/react/uimanager/BaseViewManager.java
@@ -6,8 +6,10 @@ import android.graphics.Color;
 import android.os.Build;
 import android.view.View;
 
+import com.facebook.react.bridge.ReadableArray;
 import com.facebook.react.bridge.ReadableMap;
 import com.facebook.react.uimanager.annotations.ReactProp;
+import com.facebook.react.uimanager.DisplayMetricsHolder;
 
 /**
  * Base class that should be suitable for the majority of subclasses of {@link ViewManager}.
@@ -25,6 +27,7 @@ public abstract class BaseViewManager<T extends View, C extends LayoutShadowNode
   private static final String PROP_DECOMPOSED_MATRIX_SCALE_Y = "scaleY";
   private static final String PROP_DECOMPOSED_MATRIX_TRANSLATE_X = "translateX";
   private static final String PROP_DECOMPOSED_MATRIX_TRANSLATE_Y = "translateY";
+  private static final String PROP_DECOMPOSED_MATRIX_PERSPECTIVE = "perspective";
   private static final String PROP_OPACITY = "opacity";
   private static final String PROP_ELEVATION = "elevation";
   private static final String PROP_RENDER_TO_HARDWARE_TEXTURE = "renderToHardwareTextureAndroid";
@@ -32,6 +35,8 @@ public abstract class BaseViewManager<T extends View, C extends LayoutShadowNode
   private static final String PROP_ACCESSIBILITY_COMPONENT_TYPE = "accessibilityComponentType";
   private static final String PROP_ACCESSIBILITY_LIVE_REGION = "accessibilityLiveRegion";
   private static final String PROP_IMPORTANT_FOR_ACCESSIBILITY = "importantForAccessibility";
+  private static final int PERSPECTIVE_ARRAY_INVERTED_CAMERA_DISTANCE_INDEX = 2;
+  private static final float CAMERA_DISTANCE_NORMALIZATION_MULTIPLIER = 5;
 
   // DEPRECATED
   private static final String PROP_ROTATION = "rotation";
@@ -164,6 +169,20 @@ public abstract class BaseViewManager<T extends View, C extends LayoutShadowNode
         (float) matrix.getDouble(PROP_DECOMPOSED_MATRIX_SCALE_X));
     view.setScaleY(
         (float) matrix.getDouble(PROP_DECOMPOSED_MATRIX_SCALE_Y));
+        
+    if (matrix.hasKey(PROP_DECOMPOSED_MATRIX_PERSPECTIVE)) {
+      ReadableArray perspectiveArray = matrix.getArray(PROP_DECOMPOSED_MATRIX_PERSPECTIVE);
+      if (perspectiveArray.size() > PERSPECTIVE_ARRAY_INVERTED_CAMERA_DISTANCE_INDEX) {
+        float cameraDistance = (float)(-1 / perspectiveArray.getDouble(PERSPECTIVE_ARRAY_INVERTED_CAMERA_DISTANCE_INDEX));
+        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 resetTransformMatrix(View view) {
@@ -175,4 +194,4 @@ public abstract class BaseViewManager<T extends View, C extends LayoutShadowNode
     view.setScaleX(1);
     view.setScaleY(1);
   }
-}
+}
\ No newline at end of file