From da9dd5ca0c487b5e81290ed6052a36b74d70768e Mon Sep 17 00:00:00 2001
From: Jake Wharton <jw@squareup.com>
Date: Sun, 24 Jun 2012 21:41:11 -0700
Subject: [PATCH] Clean up pivot math for scaling.

---
 .../nineoldandroids/view/animation/AnimatorProxy.java  |  4 +++-
 sample/res/layout/toggles.xml                          | 10 ++++++++--
 .../jakewharton/nineoldandroids/sample/Toggles.java    |  9 ++++++++-
 3 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/library/src/com/nineoldandroids/view/animation/AnimatorProxy.java b/library/src/com/nineoldandroids/view/animation/AnimatorProxy.java
index d5d6a77..ef3dda2 100644
--- a/library/src/com/nineoldandroids/view/animation/AnimatorProxy.java
+++ b/library/src/com/nineoldandroids/view/animation/AnimatorProxy.java
@@ -303,7 +303,9 @@ private void transformMatrix(Matrix m, View view) {
         final float sY = mScaleY;
         if ((sX != 1.0f) || (sY != 1.0f)) {
             m.postScale(sX, sY);
-            m.postTranslate(-pX, -pY);
+            final float sPX = -(pX / w) * ((sX * w) - w);
+            final float sPY = -(pY / h) * ((sY * h) - h);
+            m.postTranslate(sPX, sPY);
         }
 
         m.postTranslate(mTranslationX, mTranslationY);
diff --git a/sample/res/layout/toggles.xml b/sample/res/layout/toggles.xml
index f60ede3..ee35102 100644
--- a/sample/res/layout/toggles.xml
+++ b/sample/res/layout/toggles.xml
@@ -67,17 +67,23 @@
             android:layout_width="fill_parent"
             android:orientation="horizontal">
         <Button
-                android:id="@+id/pivot_corner"
+                android:id="@+id/pivot_zero_zero"
                 android:layout_height="wrap_content"
                 android:layout_width="0dp"
                 android:layout_weight="1"
-                android:text="Pivot Corner"/>
+                android:text="Pivot (0,0)"/>
         <Button
                 android:id="@+id/pivot_center"
                 android:layout_height="wrap_content"
                 android:layout_width="0dp"
                 android:layout_weight="1"
                 android:text="Pivot Center"/>
+        <Button
+                android:id="@+id/pivot_width_height"
+                android:layout_height="wrap_content"
+                android:layout_width="0dp"
+                android:layout_weight="1"
+                android:text="Pivot (w,h)"/>
     </LinearLayout>
     <LinearLayout
             android:layout_height="0dp"
diff --git a/sample/src/com/jakewharton/nineoldandroids/sample/Toggles.java b/sample/src/com/jakewharton/nineoldandroids/sample/Toggles.java
index c0a35e9..ca416c6 100644
--- a/sample/src/com/jakewharton/nineoldandroids/sample/Toggles.java
+++ b/sample/src/com/jakewharton/nineoldandroids/sample/Toggles.java
@@ -64,7 +64,7 @@ public void onClick(View v) {
                 ObjectAnimator.ofFloat(target, "rotation", 0, 180, 0).setDuration(duration).start();
             }
         });
-        findViewById(R.id.pivot_corner).setOnClickListener(new OnClickListener() {
+        findViewById(R.id.pivot_zero_zero).setOnClickListener(new OnClickListener() {
             @Override
             public void onClick(View v) {
                 ViewHelper.setPivotX(target, 0);
@@ -78,5 +78,12 @@ public void onClick(View v) {
                 ViewHelper.setPivotY(target, target.getHeight() / 2f);
             }
         });
+        findViewById(R.id.pivot_width_height).setOnClickListener(new OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                ViewHelper.setPivotX(target, target.getWidth());
+                ViewHelper.setPivotY(target, target.getHeight());
+            }
+        });
     }
 }