Pinch/Zoom Infrastructure & Plumbing CL

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index f9076fb9be87def8080895959ff2be042118032b..c35bef3a9848d54150a3cc7419863cfb66fa84d0 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -430,11 +430,13 @@ void LayerTreeHostImpl::StartPageScaleAnimation(gfx::Vector2d target_offset,
                                                 bool anchor_point,
                                                 float page_scale,
                                                 base::TimeDelta duration) {
-  if (!RootScrollLayer())
+  if (!InnerViewportScrollLayer())
     return;
 
-  gfx::Vector2dF scroll_total =
-      RootScrollLayer()->scroll_offset() + RootScrollLayer()->ScrollDelta();
+  // Should we attempt to set to OuterViewportScrollingLayer if it's available?
+  active_tree_->SetCurrentlyScrollingLayer(InnerViewportScrollLayer());
+
+  gfx::Vector2dF scroll_total = active_tree_->TotalScrollOffset();
   gfx::SizeF scaled_scrollable_size = active_tree_->ScrollableSize();
   gfx::SizeF viewport_size = UnscaledScrollableViewportSize();
 
@@ -1301,10 +1303,10 @@ CompositorFrameMetadata LayerTreeHostImpl::MakeCompositorFrameMetadata() const {
     metadata.overdraw_bottom_height = overdraw_bottom_height_;
   }
 
-  if (!RootScrollLayer())
+  if (!InnerViewportScrollLayer())
     return metadata;
 
-  metadata.root_scroll_offset = RootScrollLayer()->TotalScrollOffset();
+  metadata.root_scroll_offset = active_tree_->TotalScrollOffset();
 
   return metadata;
 }
@@ -1506,15 +1508,19 @@ void LayerTreeHostImpl::Readback(void* pixels,
 }
 
 bool LayerTreeHostImpl::HaveRootScrollLayer() const {
-  return !!RootScrollLayer();
+  return !!InnerViewportScrollLayer();
 }
 
 LayerImpl* LayerTreeHostImpl::RootLayer() const {
   return active_tree_->root_layer();
 }
 
-LayerImpl* LayerTreeHostImpl::RootScrollLayer() const {
-  return active_tree_->RootScrollLayer();
+LayerImpl* LayerTreeHostImpl::InnerViewportScrollLayer() const {
+  return active_tree_->InnerViewportScrollLayer();
+}
+
+LayerImpl* LayerTreeHostImpl::OuterViewportScrollLayer() const {
+  return active_tree_->OuterViewportScrollLayer();
 }
 
 LayerImpl* LayerTreeHostImpl::CurrentlyScrollingLayer() const {
@@ -1523,7 +1529,10 @@ LayerImpl* LayerTreeHostImpl::CurrentlyScrollingLayer() const {
 
 bool LayerTreeHostImpl::IsCurrentlyScrolling() const {
   return CurrentlyScrollingLayer() ||
-         (RootScrollLayer() && RootScrollLayer()->IsExternalFlingActive());
+         (InnerViewportScrollLayer() &&
+          InnerViewportScrollLayer()->IsExternalFlingActive()) ||
+         (OuterViewportScrollLayer() &&
+          OuterViewportScrollLayer()->IsExternalFlingActive());
 }
 
 // Content layers can be either directly scrollable or contained in an outer
@@ -1899,8 +1908,6 @@ void LayerTreeHostImpl::SetViewportSize(gfx::Size device_viewport_size) {
 
   device_viewport_size_ = device_viewport_size;
 
-  UpdateMaxScrollOffset();
-
   client_->OnCanDrawStateChanged(CanDraw());
   SetFullRootLayerDamage();
 }
@@ -1910,7 +1917,6 @@ void LayerTreeHostImpl::SetOverdrawBottomHeight(float overdraw_bottom_height) {
     return;
   overdraw_bottom_height_ = overdraw_bottom_height;
 
-  UpdateMaxScrollOffset();
   SetFullRootLayerDamage();
 }
 
@@ -1926,7 +1932,6 @@ void LayerTreeHostImpl::SetDeviceScaleFactor(float device_scale_factor) {
     return;
   device_scale_factor_ = device_scale_factor;
 
-  UpdateMaxScrollOffset();
   SetFullRootLayerDamage();
 }
 
@@ -1952,10 +1957,6 @@ const gfx::Transform& LayerTreeHostImpl::DrawTransform() const {
   return external_transform_;
 }
 
-void LayerTreeHostImpl::UpdateMaxScrollOffset() {
-  active_tree_->UpdateMaxScrollOffset();
-}
-
 void LayerTreeHostImpl::DidChangeTopControlsPosition() {
   SetNeedsRedraw();
   active_tree_->set_needs_update_draw_properties();
@@ -2015,7 +2016,9 @@ LayerImpl* LayerTreeHostImpl::FindScrollLayerForDeviceViewportPoint(
   if (!potentially_scrolling_layer_impl && top_controls_manager_ &&
       top_controls_manager_->content_top_offset() !=
       settings_.top_controls_height) {
-    potentially_scrolling_layer_impl = RootScrollLayer();
+    potentially_scrolling_layer_impl =
+        OuterViewportScrollLayer() ? OuterViewportScrollLayer()
+                                   : InnerViewportScrollLayer();
   }
 
   return potentially_scrolling_layer_impl;
@@ -2051,7 +2054,9 @@ InputHandler::ScrollStatus LayerTreeHostImpl::ScrollBegin(
 
   // If we want to send a DidOverscroll for this scroll it can't be ignored.
   if (!potentially_scrolling_layer_impl && settings_.always_overscroll)
-    potentially_scrolling_layer_impl = RootScrollLayer();
+    potentially_scrolling_layer_impl =
+        OuterViewportScrollLayer() ? OuterViewportScrollLayer()
+                                   : InnerViewportScrollLayer();
 
   if (potentially_scrolling_layer_impl) {
     active_tree_->SetCurrentlyScrollingLayer(
@@ -2158,8 +2163,10 @@ bool LayerTreeHostImpl::ScrollBy(gfx::Point viewport_point,
   gfx::Vector2dF unused_root_delta;
   bool did_scroll_x = false;
   bool did_scroll_y = false;
-  bool consume_by_top_controls = top_controls_manager_ &&
-      (CurrentlyScrollingLayer() == RootScrollLayer() || scroll_delta.y() < 0);
+  bool consume_by_top_controls =
+      top_controls_manager_ &&
+      (CurrentlyScrollingLayer() == InnerViewportScrollLayer() ||
+       scroll_delta.y() < 0);
 
   for (LayerImpl* layer_impl = CurrentlyScrollingLayer();
        layer_impl;
@@ -2167,12 +2174,18 @@ bool LayerTreeHostImpl::ScrollBy(gfx::Point viewport_point,
     if (!layer_impl->scrollable())
       continue;
 
-    if (layer_impl == RootScrollLayer()) {
+    if (layer_impl == InnerViewportScrollLayer()) {
       // Only allow bubble scrolling when the scroll is in the direction to make
       // the top controls visible.
-      if (consume_by_top_controls && layer_impl == RootScrollLayer()) {
-        pending_delta = top_controls_manager_->ScrollBy(pending_delta);
-        UpdateMaxScrollOffset();
+      gfx::Vector2dF applied_delta;
+      gfx::Vector2dF excess_delta;
+      if (consume_by_top_controls && layer_impl == InnerViewportScrollLayer()) {
+        excess_delta = top_controls_manager_->ScrollBy(pending_delta);
+        applied_delta = pending_delta - excess_delta;
+        pending_delta = excess_delta;
+        // Force updating of vertical adjust values if needed.
+        if (applied_delta.y() != 0)
+            layer_impl->ScrollbarParametersDidChange();
       }
       // Track root layer deltas for reporting overscroll.
       unused_root_delta = pending_delta;
@@ -2206,7 +2219,8 @@ bool LayerTreeHostImpl::ScrollBy(gfx::Point viewport_point,
         break;
     }
 
-    if (layer_impl == RootScrollLayer())
+    if (layer_impl == InnerViewportScrollLayer() ||
+        layer_impl == OuterViewportScrollLayer())
       unused_root_delta.Subtract(applied_delta);
 
     did_lock_scrolling_layer_ = true;
@@ -2273,10 +2287,10 @@ bool LayerTreeHostImpl::ScrollVerticallyByPage(gfx::Point viewport_point,
     if (!layer_impl->scrollable())
       continue;
 
-    if (!layer_impl->vertical_scrollbar_layer())
+    if (!layer_impl->HasScrollbar(VERTICAL))
       continue;
 
-    float height = layer_impl->vertical_scrollbar_layer()->bounds().height();
+    float height = layer_impl->clip_height();
 
     // These magical values match WebKit and are designed to scroll nearly the
     // entire visible content height but leave a bit of overlap.
@@ -2332,8 +2346,8 @@ InputHandler::ScrollStatus LayerTreeHostImpl::FlingScrollBegin() {
     return ScrollIgnored;
 
   if (settings_.ignore_root_layer_flings &&
-      active_tree_->CurrentlyScrollingLayer() ==
-          active_tree_->RootScrollLayer()) {
+      (active_tree_->CurrentlyScrollingLayer() == InnerViewportScrollLayer() ||
+       active_tree_->CurrentlyScrollingLayer() == OuterViewportScrollLayer())) {
     ClearCurrentlyScrollingLayer();
     return ScrollIgnored;
   }
@@ -2408,11 +2422,14 @@ void LayerTreeHostImpl::MouseMoveAt(gfx::Point viewport_point) {
   if (!animation_controller)
     return;
 
-  float distance_to_scrollbar = std::min(
-      DeviceSpaceDistanceToLayer(device_viewport_point,
-          scroll_layer_impl->horizontal_scrollbar_layer()),
-      DeviceSpaceDistanceToLayer(device_viewport_point,
-          scroll_layer_impl->vertical_scrollbar_layer()));
+  // TODO(wjmaclean) Is it ok to choose distance from more than two scrollbars?
+  float distance_to_scrollbar = std::numeric_limits<float>::max();
+  for (LayerImpl::ScrollbarSet::iterator it =
+           scroll_layer_impl->scrollbars()->begin();
+       it != scroll_layer_impl->scrollbars()->end();
+       ++it)
+    distance_to_scrollbar = std::min(distance_to_scrollbar,
+        DeviceSpaceDistanceToLayer(device_viewport_point, *it));
 
   bool should_animate = animation_controller->DidMouseMoveNear(
       CurrentPhysicalTimeTicks(), distance_to_scrollbar / device_scale_factor_);
@@ -2447,7 +2464,13 @@ void LayerTreeHostImpl::PinchGestureBegin() {
   previous_pinch_anchor_ = gfx::Point();
   client_->RenewTreePriority();
   pinch_gesture_end_should_clear_scrolling_layer_ = !CurrentlyScrollingLayer();
-  active_tree_->SetCurrentlyScrollingLayer(RootScrollLayer());
+  if (active_tree_->OuterViewportScrollLayer()) {
+    active_tree_->SetCurrentlyScrollingLayer(
+        active_tree_->OuterViewportScrollLayer());
+  } else {
+    active_tree_->SetCurrentlyScrollingLayer(
+        active_tree_->InnerViewportScrollLayer());
+  }
   if (top_controls_manager_)
     top_controls_manager_->PinchBegin();
 }
@@ -2456,7 +2479,11 @@ void LayerTreeHostImpl::PinchGestureUpdate(float magnify_delta,
                                            gfx::Point anchor) {
   TRACE_EVENT0("cc", "LayerTreeHostImpl::PinchGestureUpdate");
 
-  if (!RootScrollLayer())
+  LayerImpl* pinch_scroll_layer = CurrentlyScrollingLayer();
+  if (!pinch_scroll_layer)
+    pinch_scroll_layer = InnerViewportScrollLayer();
+
+  if (!pinch_scroll_layer)
     return;
 
   // Keep the center-of-pinch anchor specified by (x, y) in a stable
@@ -2473,8 +2500,29 @@ void LayerTreeHostImpl::PinchGestureUpdate(float magnify_delta,
   previous_pinch_anchor_ = anchor;
 
   move.Scale(1 / active_tree_->page_scale_factor());
-
-  RootScrollLayer()->ScrollBy(move);
+  // When shrinking the page, the current scroll offset of the inner viewport
+  // scroll layer may need to be adjusted so that it doesn't exceed its maximum
+  // at the new page scale factor.
+  if (magnify_delta < 1.f) {
+    // If clamping the inner viewport scroll offset causes a change, it should
+    // be accounted for from the intended move.
+    move -= InnerViewportScrollLayer()->ClampScrollToMaxScrollOffset();
+  }
+
+  // We manually manage the bubbling behaviour here as it is different to that
+  // implemented in LayerTreeHostImpl::ScrollBy(). Specifically:
+  // 1) we want to explicit limit the bubbling to the outer/inner viewports,
+  // 2) we don't want the directional limitations on the unused parts that
+  //    ScrollBy() implements, and
+  // 3) pinching should not engage the top controls manager.
+  gfx::Vector2dF unused = pinch_scroll_layer->ScrollBy(move);
+
+  if (!unused.IsZero() && pinch_scroll_layer == OuterViewportScrollLayer()) {
+    InnerViewportScrollLayer()->ScrollBy(unused);
+    InnerViewportScrollLayer()->ClampScrollToMaxScrollOffset();
+    active_tree_->SetCurrentlyScrollingLayer(
+        active_tree_->InnerViewportScrollLayer());
+  }
 
   client_->SetNeedsCommitOnImplThread();
   SetNeedsRedraw();
@@ -2526,12 +2574,11 @@ void LayerTreeHostImpl::SetFullRootLayerDamage() {
 }
 
 void LayerTreeHostImpl::AnimatePageScale(base::TimeTicks time) {
-  if (!page_scale_animation_ || !RootScrollLayer())
+  if (!page_scale_animation_)
     return;
 
   double monotonic_time = (time - base::TimeTicks()).InSecondsF();
-  gfx::Vector2dF scroll_total = RootScrollLayer()->scroll_offset() +
-                                RootScrollLayer()->ScrollDelta();
+  gfx::Vector2dF scroll_total = active_tree_->TotalScrollOffset();
 
   if (!page_scale_animation_->IsAnimationStarted())
     page_scale_animation_->StartAnimation(monotonic_time);
@@ -2542,7 +2589,7 @@ void LayerTreeHostImpl::AnimatePageScale(base::TimeTicks time) {
   gfx::Vector2dF next_scroll =
       page_scale_animation_->ScrollOffsetAtTime(monotonic_time);
 
-  RootScrollLayer()->ScrollBy(next_scroll - scroll_total);
+  ScrollBy(gfx::Point(), next_scroll - scroll_total);
   SetNeedsRedraw();
 
   if (page_scale_animation_->IsAnimationCompleteAtTime(monotonic_time)) {
@@ -2553,14 +2600,14 @@ void LayerTreeHostImpl::AnimatePageScale(base::TimeTicks time) {
 }
 
 void LayerTreeHostImpl::AnimateTopControls(base::TimeTicks time) {
-  if (!top_controls_manager_ || !RootScrollLayer())
+  if (!top_controls_manager_)
     return;
   gfx::Vector2dF scroll = top_controls_manager_->Animate(time);
-  UpdateMaxScrollOffset();
-  if (RootScrollLayer()->TotalScrollOffset().y() == 0.f)
+  if (active_tree_->TotalScrollOffset().y() == 0.f)
     return;
-  RootScrollLayer()->ScrollBy(gfx::ScaleVector2d(
-      scroll, 1.f / active_tree_->total_page_scale_factor()));
+  ScrollBy(gfx::Point(),
+           gfx::ScaleVector2d(scroll,
+                              1.f / active_tree_->total_page_scale_factor()));
 }
 
 void LayerTreeHostImpl::AnimateLayers(base::TimeTicks monotonic_time,