Proper hit testing for translated layers.

Fixes Flipboard#22

Author: Michael Johnston

lib/hitTest.js

@@ -21,7 +21,13 @@ function hitTest (e, rootLayer, rootNode) {
  touchX -= rootNodeBox.left;
  touchY -= rootNodeBox.top;
  }
- return getLayerAtPoint(rootLayer, e.type, FrameUtils.make(touchX, touchY, 1, 1));
+ return getLayerAtPoint(
+ rootLayer,
+ e.type,
+ FrameUtils.make(touchX, touchY, 1, 1),
+ rootLayer.translateX || 0,
+ rootLayer.translateY || 0
+ );
 }
 
 /**
@@ -48,11 +54,11 @@ function getHitHandle (type) {
 /**
  * @private
  */
-function getLayerAtPoint (root, type, point) {
+function getLayerAtPoint (root, type, point, tx, ty) {
  var layer = null;
  var hitHandle = getHitHandle(type);
  var sortedChildren;
- var hitFrame = root.frame;
+ var hitFrame = FrameUtils.clone(root.frame);
 
  // Early bail for non-visible layers
  if (typeof root.alpha === 'number' && root.alpha < 0.01) {
@@ -63,7 +69,13 @@ function getLayerAtPoint (root, type, point) {
  if (root.children) {
  sortedChildren = root.children.slice().reverse().sort(sortByZIndexDescending);
  for (var i=0, len=sortedChildren.length; i < len; i++) {
- layer = getLayerAtPoint(sortedChildren[i], type, point);
+ layer = getLayerAtPoint(
+ sortedChildren[i],
+ type,
+ point,
+ tx + (root.translateX || 0),
+ ty + (root.translateY || 0)
+ );
  if (layer) {
  break;
  }
@@ -78,6 +90,15 @@ function getLayerAtPoint (root, type, point) {
  );
  }
 
+ // Check for x/y translation
+ if (tx) {
+ hitFrame.x += tx;
+ }
+
+ if (ty) {
+ hitFrame.y += ty;
+ }
+
  // No child layer at the given point. Try the parent layer.
  if (!layer && root[hitHandle] && FrameUtils.intersects(hitFrame, point)) {
  layer = root;