Implement pinch-zoom scaling for main-frame scrollbars and pinch-zoom overlay scrollbars.

cc/layer_tree_impl.cc

Index: cc/layer_tree_impl.cc
diff --git a/cc/layer_tree_impl.cc b/cc/layer_tree_impl.cc
index 8840c19028821ef1d87111c2e6c12100ad02ace8..913202d8c98f4984f41ea966ebc4356ad897f993 100644
--- a/cc/layer_tree_impl.cc
+++ b/cc/layer_tree_impl.cc
@@ -5,9 +5,15 @@
 #include "cc/layer_tree_impl.h"
 
 #include "base/debug/trace_event.h"
+#include "cc/animation.h"
+#include "cc/animation_id_provider.h"
 #include "cc/heads_up_display_layer_impl.h"
+#include "cc/keyframed_animation_curve.h"
+#include "cc/layer.h"
 #include "cc/layer_tree_host_common.h"
 #include "cc/layer_tree_host_impl.h"
+#include "cc/pinch_zoom_scrollbar.h"
+#include "cc/scrollbar_layer_impl.h"
 #include "ui/gfx/vector2d_conversions.h"
 
 namespace cc {
@@ -20,6 +26,8 @@ LayerTreeImpl::LayerTreeImpl(LayerTreeHostImpl* layer_tree_host_impl)
       currently_scrolling_layer_(0),
       background_color_(0),
       has_transparent_background_(false),
+      pinch_zoom_scrollbar_horizontal_layer_id_(Layer::INVALID_ID),
+      pinch_zoom_scrollbar_vertical_layer_id_(Layer::INVALID_ID),
       page_scale_factor_(1),
       page_scale_delta_(1),
       sent_page_scale_delta_(1),
@@ -116,6 +124,11 @@ void LayerTreeImpl::PushPropertiesTo(LayerTreeImpl* target_tree) {
             target_tree->RootLayer(), hud_layer()->id())));
   else
     target_tree->set_hud_layer(NULL);
+
+  target_tree->SetPinchZoomHorizontalLayerId(
+      pinch_zoom_scrollbar_horizontal_layer_id_);
+  target_tree->SetPinchZoomVerticalLayerId(
+      pinch_zoom_scrollbar_vertical_layer_id_);
 }
 
 LayerImpl* LayerTreeImpl::RootScrollLayer() {
@@ -334,6 +347,10 @@ void LayerTreeImpl::DidBecomeActive() {
     DidBecomeActiveRecursive(RootLayer());
   FindRootScrollLayer();
   UpdateMaxScrollOffset();
+  // Main thread scrolls do not get handled in LayerTreeHostImpl, so after
+  // each commit (and after the root scroll layer has its max scroll offset
+  // set), we need to update pinch zoom scrollbars.
+  UpdatePinchZoomScrollbars();
 }
 
 bool LayerTreeImpl::ContentsTexturesPurged() const {
@@ -486,4 +503,118 @@ scoped_ptr<base::Value> LayerTreeImpl::AsValue() const {
   return state.PassAs<base::Value>();
 }
 
+void LayerTreeImpl::DidBeginScroll() {
+  if (HasPinchZoomScrollbars())
+    FadeInPinchZoomScrollbars();
+}
+
+void LayerTreeImpl::DidUpdateScroll() {
+  if (HasPinchZoomScrollbars())
+    UpdatePinchZoomScrollbars();
+}
+
+void LayerTreeImpl::DidEndScroll() {
+  if (HasPinchZoomScrollbars())
+    FadeOutPinchZoomScrollbars();
+}
+
+void LayerTreeImpl::SetPinchZoomHorizontalLayerId(int layer_id) {
+  pinch_zoom_scrollbar_horizontal_layer_id_ = layer_id;
+}
+
+ScrollbarLayerImpl* LayerTreeImpl::PinchZoomScrollbarHorizontal() {
+  return static_cast<ScrollbarLayerImpl*>(LayerById(
+    pinch_zoom_scrollbar_horizontal_layer_id_));
+}
+
+void LayerTreeImpl::SetPinchZoomVerticalLayerId(int layer_id) {
+  pinch_zoom_scrollbar_vertical_layer_id_ = layer_id;
+}
+
+ScrollbarLayerImpl* LayerTreeImpl::PinchZoomScrollbarVertical() {
+  return static_cast<ScrollbarLayerImpl*>(LayerById(
+    pinch_zoom_scrollbar_vertical_layer_id_));
+}
+
+void LayerTreeImpl::UpdatePinchZoomScrollbars() {
+  LayerImpl* root_scroll_layer = RootScrollLayer();
+  if (!root_scroll_layer)
+    return;
+
+  if (ScrollbarLayerImpl* scrollbar = PinchZoomScrollbarHorizontal()) {
+    scrollbar->SetCurrentPos(root_scroll_layer->scroll_offset().x());
+    scrollbar->SetTotalSize(root_scroll_layer->bounds().width());
+    scrollbar->SetMaximum(root_scroll_layer->max_scroll_offset().x());
+  }
+  if (ScrollbarLayerImpl* scrollbar = PinchZoomScrollbarVertical()) {
+    scrollbar->SetCurrentPos(root_scroll_layer->scroll_offset().y());
+    scrollbar->SetTotalSize(root_scroll_layer->bounds().height());
+    scrollbar->SetMaximum(root_scroll_layer->max_scroll_offset().y());
+  }
+}
+
+static scoped_ptr<Animation> MakePinchZoomFadeAnimation(
+    float start_opacity, float end_opacity) {
+  scoped_ptr<KeyframedFloatAnimationCurve> curve =
+    KeyframedFloatAnimationCurve::Create();
+  curve->AddKeyframe(FloatKeyframe::Create(
+    0, start_opacity, EaseInTimingFunction::create()));
+  curve->AddKeyframe(FloatKeyframe::Create(
+    PinchZoomScrollbar::kFadeDurationInSeconds, end_opacity,
+    EaseInTimingFunction::create()));
+
+  scoped_ptr<Animation> animation = Animation::Create(
+      curve.PassAs<AnimationCurve>(), AnimationIdProvider::NextAnimationId(),
+      0, Animation::Opacity);
+  animation->set_is_impl_only(true);
+
+  return animation.Pass();
+}
+
+static void StartFadeInAnimation(ScrollbarLayerImpl* layer) {
+  DCHECK(layer);
+  float start_opacity = layer->opacity();
+  LayerAnimationController* controller = layer->layer_animation_controller();
+  // TODO() It shouldn't be necessary to manually remove the old animation.
+  if (Animation* animation = controller->GetAnimation(Animation::Opacity))
+    controller->RemoveAnimation(animation->id());
+  controller->AddAnimation(MakePinchZoomFadeAnimation(start_opacity,
+    PinchZoomScrollbar::kDefaultOpacity));
+}
+
+void LayerTreeImpl::FadeInPinchZoomScrollbars() {
+  if (!HasPinchZoomScrollbars() || page_scale_factor_ == 1)
+    return;
+
+  StartFadeInAnimation(PinchZoomScrollbarHorizontal());
+  StartFadeInAnimation(PinchZoomScrollbarVertical());
+}
+
+static void StartFadeOutAnimation(LayerImpl* layer) {
+  float opacity = layer->opacity();
+  if (!opacity)
+    return;
+
+  LayerAnimationController* controller = layer->layer_animation_controller();
+  // TODO(wjmaclean) It shouldn't be necessary to manually remove the old
+  // animation.
+  if (Animation* animation = controller->GetAnimation(Animation::Opacity))
+    controller->RemoveAnimation(animation->id());
+  controller->AddAnimation(MakePinchZoomFadeAnimation(opacity, 0));
+}
+
+void LayerTreeImpl::FadeOutPinchZoomScrollbars() {
+  if (!HasPinchZoomScrollbars())
+    return;
+
+  StartFadeOutAnimation(PinchZoomScrollbarHorizontal());
+  StartFadeOutAnimation(PinchZoomScrollbarVertical());
+}
+
+bool LayerTreeImpl::HasPinchZoomScrollbars() const {
+  return pinch_zoom_scrollbar_horizontal_layer_id_ != Layer::INVALID_ID &&
+         pinch_zoom_scrollbar_vertical_layer_id_ != Layer::INVALID_ID;
+}
+
+
 } // namespace cc