Scroll offset animation curve retargeting.

cc/trees/layer_tree_host_impl.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_host_impl.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/basictypes.h"
@@ skipping 2302 matching lines @@
     client_->RenewTreePriority();
     UMA_HISTOGRAM_BOOLEAN("TryScroll.SlowScroll", false);
     return ScrollStarted;
   }
   return ScrollIgnored;
 }
 
 InputHandler::ScrollStatus LayerTreeHostImpl::ScrollAnimated(
     const gfx::Point& viewport_point,
     const gfx::Vector2dF& scroll_delta) {
-  if (CurrentlyScrollingLayer()) {
-    // TODO(skobes): Update the target of the existing animation.
-    return ScrollIgnored;
+  if (LayerImpl* layer_impl = CurrentlyScrollingLayer()) {
+    Animation* animation =
+        layer_impl->layer_animation_controller()->GetAnimation(
+            Animation::ScrollOffset);
+    if (!animation)
+      return ScrollIgnored;
+
+    ScrollOffsetAnimationCurve* curve =
+        animation->curve()->ToScrollOffsetAnimationCurve();
+
+    gfx::Vector2dF new_target = curve->target_value() + scroll_delta;
+    new_target.SetToMax(gfx::Vector2dF());
+    new_target.SetToMin(layer_impl->MaxScrollOffset());
+
+    curve->UpdateTarget(
+        animation->TrimTimeToCurrentIteration(CurrentFrameTimeTicks()),
+        new_target);
+
+    return ScrollStarted;
   }
   // ScrollAnimated is only used for wheel scrolls. We use the same bubbling
   // behavior as ScrollBy to determine which layer to animate, but we do not
   // do the Android-specific things in ScrollBy like showing top controls.
   InputHandler::ScrollStatus scroll_status = ScrollBegin(viewport_point, Wheel);
   if (scroll_status == ScrollStarted) {
     gfx::Vector2dF pending_delta = scroll_delta;
     for (LayerImpl* layer_impl = CurrentlyScrollingLayer(); layer_impl;
          layer_impl = layer_impl->parent()) {
       if (!layer_impl->scrollable())
@@ skipping 16 matching lines @@
       }
 
       active_tree_->SetCurrentlyScrollingLayer(layer_impl);
 
       scoped_ptr<ScrollOffsetAnimationCurve> curve =
           ScrollOffsetAnimationCurve::Create(target_offset,
                                              EaseInOutTimingFunction::Create());
       curve->SetInitialValue(current_offset);
 
       scoped_ptr<Animation> animation =
-          Animation::Create(curve->Clone().Pass(),
+          Animation::Create(curve.PassAs<AnimationCurve>(),
                             AnimationIdProvider::NextAnimationId(),
                             AnimationIdProvider::NextGroupId(),
                             Animation::ScrollOffset);
       animation->set_is_impl_only(true);
 
       layer_impl->layer_animation_controller()->AddAnimation(animation.Pass());
 
       SetNeedsAnimate();
       return ScrollStarted;
     }
@@ skipping 898 matching lines @@
 }
 
 void LayerTreeHostImpl::UnregisterPictureLayerImpl(PictureLayerImpl* layer) {
   std::vector<PictureLayerImpl*>::iterator it =
       std::find(picture_layers_.begin(), picture_layers_.end(), layer);
   DCHECK(it != picture_layers_.end());
   picture_layers_.erase(it);
 }
 
 }  // namespace cc