Made top controls work with virtual viewport pinch-to-zoom. (Chromium)

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 542143cea7af64c6cfc63ed93ba67bb66b77e5e8..ff3f99f803543494ce5d9547a7939281c8d49d7e 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -78,6 +78,42 @@
 namespace cc {
 namespace {
 
+// Small helper class that saves the current viewport location as the user sees
+// it and resets to the same location.
+class ViewportAnchor {
+ public:
+  ViewportAnchor(LayerImpl* inner_scroll, LayerImpl* outer_scroll)
+  : inner_(inner_scroll),
+    outer_(outer_scroll) {
+    viewport_in_content_coordinates_ = inner_->TotalScrollOffset();
+
+    if (outer_)
+      viewport_in_content_coordinates_ += outer_->TotalScrollOffset();
+  }
+
+  void ResetViewportToAnchoredPosition() {
+    DCHECK(outer_);
+
+    inner_->ClampScrollToMaxScrollOffset();
+    outer_->ClampScrollToMaxScrollOffset();
+
+    gfx::ScrollOffset viewport_location = inner_->TotalScrollOffset() +
+                                          outer_->TotalScrollOffset();
+
+    gfx::Vector2dF delta =
+        viewport_in_content_coordinates_.DeltaFrom(viewport_location);
+
+    delta = outer_->ScrollBy(delta);
+    inner_->ScrollBy(delta);
+  }
+
+ private:
+  LayerImpl* inner_;
+  LayerImpl* outer_;
+  gfx::ScrollOffset viewport_in_content_coordinates_;
+};
+
+
 void DidVisibilityChange(LayerTreeHostImpl* id, bool visible) {
   if (visible) {
     TRACE_EVENT_ASYNC_BEGIN1("webkit",
@@ -1654,16 +1690,41 @@ void LayerTreeHostImpl::WillBeginImplFrame(const BeginFrameArgs& args) {
   begin_impl_frame_interval_ = args.interval;
 }
 
-void LayerTreeHostImpl::UpdateInnerViewportContainerSize() {
-  LayerImpl* container_layer = active_tree_->InnerViewportContainerLayer();
-  if (!container_layer)
+void LayerTreeHostImpl::UpdateViewportContainerSizes() {
+  LayerImpl* inner_container = active_tree_->InnerViewportContainerLayer();
+  LayerImpl* outer_container = active_tree_->OuterViewportContainerLayer();
+
+  if (!inner_container || !top_controls_manager_)
     return;
 
-  if (top_controls_manager_) {
-    container_layer->SetBoundsDelta(
-        gfx::Vector2dF(0, active_tree_->top_controls_layout_height() -
-            active_tree_->total_top_controls_content_offset()));
-  }
+  ViewportAnchor anchor(InnerViewportScrollLayer(),
+                        OuterViewportScrollLayer());
+
+  // Adjust the inner viewport by shrinking/expanding the container to account
+  // for the change in top controls height since the last Resize from Blink.
+  inner_container->SetBoundsDelta(
+      gfx::Vector2dF(0, active_tree_->top_controls_layout_height() -
+          active_tree_->total_top_controls_content_offset()));
+
+  if (!outer_container || outer_container->BoundsForScrolling().IsEmpty())
+    return;
+
+  // Adjust the outer viewport container as well, since adjusting only the
+  // inner may cause its bounds to exceed those of the outer, causing scroll
+  // clamping. We adjust it so it maintains the same aspect ratio as the
+  // inner viewport.
+  float aspect_ratio = inner_container->BoundsForScrolling().width() /
+      inner_container->BoundsForScrolling().height();
+  float target_height = outer_container->BoundsForScrolling().width() /
+      aspect_ratio;
+  float current_outer_height = outer_container->BoundsForScrolling().height() -
+      outer_container->bounds_delta().y();
+  gfx::Vector2dF delta(0, target_height - current_outer_height);
+
+  outer_container->SetBoundsDelta(delta);
+  active_tree_->InnerViewportScrollLayer()->SetBoundsDelta(delta);
+
+  anchor.ResetViewportToAnchoredPosition();
 }
 
 void LayerTreeHostImpl::SetTopControlsLayoutHeight(float height) {
@@ -1671,7 +1732,7 @@ void LayerTreeHostImpl::SetTopControlsLayoutHeight(float height) {
     return;
 
   active_tree_->set_top_controls_layout_height(height);
-  UpdateInnerViewportContainerSize();
+  UpdateViewportContainerSizes();
   SetFullRootLayerDamage();
 }
 
@@ -1792,7 +1853,7 @@ void LayerTreeHostImpl::ActivateSyncTree() {
           top_controls_manager_->top_controls_height());
     }
 
-    UpdateInnerViewportContainerSize();
+    UpdateViewportContainerSizes();
   } else {
     active_tree_->ProcessUIResourceRequestQueue();
   }
@@ -2155,7 +2216,7 @@ void LayerTreeHostImpl::SetViewportSize(const gfx::Size& device_viewport_size) {
 
   device_viewport_size_ = device_viewport_size;
 
-  UpdateInnerViewportContainerSize();
+  UpdateViewportContainerSizes();
   client_->OnCanDrawStateChanged(CanDraw());
   SetFullRootLayerDamage();
   active_tree_->set_needs_update_draw_properties();
@@ -2206,7 +2267,7 @@ const gfx::Transform& LayerTreeHostImpl::DrawTransform() const {
 }
 
 void LayerTreeHostImpl::DidChangeTopControlsPosition() {
-  UpdateInnerViewportContainerSize();
+  UpdateViewportContainerSizes();
   SetNeedsRedraw();
   SetNeedsAnimate();
   active_tree_->set_needs_update_draw_properties();
@@ -2502,6 +2563,31 @@ static gfx::Vector2dF ScrollLayerWithLocalDelta(LayerImpl* layer_impl,
   return layer_impl->ScrollDelta() - previous_delta;
 }
 
+bool LayerTreeHostImpl::ShouldTopControlsConsumeScroll(
+    const gfx::Vector2dF& scroll_delta) const {
+  DCHECK(CurrentlyScrollingLayer());
+
+  if (!top_controls_manager_)
+    return false;
+
+  // Always consume if it's in the direction to show the top controls.
+  if (scroll_delta.y() < 0)
+    return true;
+
+  if (CurrentlyScrollingLayer() != InnerViewportScrollLayer() &&
+      CurrentlyScrollingLayer() != OuterViewportScrollLayer())
+    return false;
+
+  if (InnerViewportScrollLayer()->MaxScrollOffset().y() > 0)
+    return true;
+
+  if (OuterViewportScrollLayer() &&
+      OuterViewportScrollLayer()->MaxScrollOffset().y() > 0)
+    return true;
+
+  return false;
+}
+
 bool LayerTreeHostImpl::ScrollBy(const gfx::Point& viewport_point,
                                  const gfx::Vector2dF& scroll_delta) {
   TRACE_EVENT0("cc", "LayerTreeHostImpl::ScrollBy");
@@ -2513,14 +2599,8 @@ bool LayerTreeHostImpl::ScrollBy(const gfx::Point& viewport_point,
   bool did_scroll_x = false;
   bool did_scroll_y = false;
   bool did_scroll_top_controls = false;
-  // TODO(wjmaclean) Should we guard against CurrentlyScrollingLayer() == 0
-  // here?
-  bool consume_by_top_controls =
-      top_controls_manager_ &&
-      (((CurrentlyScrollingLayer() == InnerViewportScrollLayer() ||
-         CurrentlyScrollingLayer() == OuterViewportScrollLayer()) &&
-        InnerViewportScrollLayer()->MaxScrollOffset().y() > 0) ||
-       scroll_delta.y() < 0);
+
+  bool consume_by_top_controls = ShouldTopControlsConsumeScroll(scroll_delta);
 
   for (LayerImpl* layer_impl = CurrentlyScrollingLayer();
        layer_impl;
@@ -2528,23 +2608,20 @@ bool LayerTreeHostImpl::ScrollBy(const gfx::Point& viewport_point,
     if (!layer_impl->scrollable())
       continue;
 
-    if (layer_impl == InnerViewportScrollLayer()) {
-      // Only allow bubble scrolling when the scroll is in the direction to make
-      // the top controls visible.
-      gfx::Vector2dF applied_delta;
-      gfx::Vector2dF excess_delta;
+    if (layer_impl == InnerViewportScrollLayer() ||
+        layer_impl == OuterViewportScrollLayer()) {
       if (consume_by_top_controls) {
-        excess_delta = top_controls_manager_->ScrollBy(pending_delta);
-        applied_delta = pending_delta - excess_delta;
+        gfx::Vector2dF excess_delta =
+            top_controls_manager_->ScrollBy(pending_delta);
+        gfx::Vector2dF applied_delta = pending_delta - excess_delta;
         pending_delta = excess_delta;
         // Force updating of vertical adjust values if needed.
-        if (applied_delta.y() != 0) {
+        if (applied_delta.y() != 0)
           did_scroll_top_controls = true;
-          layer_impl->ScrollbarParametersDidChange(false);
-        }
       }
       // Track root layer deltas for reporting overscroll.
-      unused_root_delta = pending_delta;
+      if (layer_impl == InnerViewportScrollLayer())
+        unused_root_delta = pending_delta;
     }
 
     gfx::Vector2dF applied_delta;