clip canvas draw bounds to the AE canvas

Summary:
this adds clipping that will respect the bounds of the after effects
canvas, rather than drawing in all allotted space of the drawable
Closes #84

Differential Revision: D4439895

Pulled By: LazyChild

fbshipit-source-id: c9de07b227a3d382716b69a816eecaf796536ded

android/keyframes/src/main/java/com/facebook/keyframes/KeyframesDrawable.java

@@ -94,7 +94,7 @@ public class KeyframesDrawable extends Drawable
   private float mScaleFromCenter;
   private float mScaleFromEnd;
   private final Map<String, FeatureConfig> mFeatureConfigs;
-
+  private boolean mClipToAECanvas;
 
   private boolean mHasInitialized = false;
 
@@ -130,6 +130,7 @@ public class KeyframesDrawable extends Drawable
     }
 
     setMaxFrameRate(builder.getMaxFrameRate());
+    mClipToAECanvas = builder.getExperimentalFeatures().getClipToAECanvas();
   }
 
   /**
@@ -170,6 +171,13 @@ public void setDirectionalScale(
   public void draw(Canvas canvas) {
     Rect currBounds = getBounds();
     canvas.translate(currBounds.left, currBounds.top);
+    if (mClipToAECanvas) {
+      canvas.clipRect(
+          0,
+          0,
+          mKFImage.getCanvasSize()[0] * mScale * mScaleFromEnd * mScaleFromCenter,
+          mKFImage.getCanvasSize()[1] * mScale * mScaleFromEnd * mScaleFromCenter);
+    }
     KFPath pathToDraw;
     FeatureState featureState;
     for (int i = 0, len = mFeatureStateList.size(); i < len; i++) {

android/keyframes/src/main/java/com/facebook/keyframes/KeyframesDrawableBuilder.java

@@ -69,6 +69,7 @@ ExperimentalFeatures getExperimentalFeatures() {
    */
   public class ExperimentalFeatures {
     private Map<String, KeyframesDrawable.FeatureConfig> mParticleFeatureConfigs;
+    private boolean mClipToAECanvas = false;
 
     public KeyframesDrawable build() {
       return KeyframesDrawableBuilder.this.build();
@@ -88,5 +89,14 @@ public ExperimentalFeatures withParticleFeatureConfigs(
     Map<String, KeyframesDrawable.FeatureConfig> getParticleFeatureConfigs() {
       return mParticleFeatureConfigs;
     }
+
+    public ExperimentalFeatures clipToAECanvas() {
+      mClipToAECanvas = true;
+      return ExperimentalFeatures.this;
+    }
+
+    boolean getClipToAECanvas() {
+      return mClipToAECanvas;
+    }
   }
 }