Support bottom-right anchored fixed-position elements during a pinch gesture

cc/layers/layer.cc

 // Copyright 2010 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/layers/layer.h"
 
 #include <algorithm>
 
 #include "base/metrics/histogram.h"
 #include "cc/animation/animation.h"
@@ skipping 24 matching lines @@
       parent_(NULL),
       layer_tree_host_(NULL),
       scrollable_(false),
       should_scroll_on_main_thread_(false),
       have_wheel_event_handlers_(false),
       anchor_point_(0.5f, 0.5f),
       background_color_(0),
       opacity_(1.f),
       anchor_point_z_(0.f),
       is_container_for_fixed_position_layers_(false),
-      fixed_to_container_layer_(false),
       is_drawable_(false),
       masks_to_bounds_(false),
       contents_opaque_(false),
       double_sided_(true),
       preserves_3d_(false),
       use_parent_backface_visibility_(false),
       draw_checkerboard_for_missing_tiles_(false),
       force_render_surface_(false),
       replica_layer_(NULL),
       raster_scale_(1.f),
@@ skipping 353 matching lines @@
   SetNeedsCommit();
 }
 
 void Layer::SetPosition(gfx::PointF position) {
   if (position_ == position)
     return;
   position_ = position;
   SetNeedsCommit();
 }
 
+bool Layer::IsContainerForFixedPositionLayers() const {
+  if (!transform_.IsIdentityOrTranslation())
+    return true;
+  if (parent_ && !parent_->sublayer_transform_.IsIdentityOrTranslation())
+    return true;
+  return is_container_for_fixed_position_layers_;
+}
+
 void Layer::SetSublayerTransform(const gfx::Transform& sublayer_transform) {
   if (sublayer_transform_ == sublayer_transform)
     return;
   sublayer_transform_ = sublayer_transform;
   SetNeedsCommit();
 }
 
 void Layer::SetTransform(const gfx::Transform& transform) {
   if (transform_ == transform)
     return;
@@ skipping 97 matching lines @@
 
   // Simply mark the contents as dirty. For non-root layers, the call to
   // SetNeedsCommit will schedule a fresh compositing pass.
   // For the root layer, SetNeedsCommit has no effect.
   if (DrawsContent() && !update_rect_.IsEmpty())
     SetNeedsCommit();
 }
 
 bool Layer::DescendantIsFixedToContainerLayer() const {
   for (size_t i = 0; i < children_.size(); ++i) {
-    if (children_[i]->fixed_to_container_layer() ||
+    if (children_[i]->position_constraint_.is_fixed_position() ||
         children_[i]->DescendantIsFixedToContainerLayer())
       return true;
   }
   return false;
 }
 
 void Layer::SetIsContainerForFixedPositionLayers(bool container) {
   if (is_container_for_fixed_position_layers_ == container)
     return;
   is_container_for_fixed_position_layers_ = container;
 
   if (layer_tree_host_ && layer_tree_host_->CommitRequested())
     return;
 
   // Only request a commit if we have a fixed positioned descendant.
   if (DescendantIsFixedToContainerLayer())
     SetNeedsCommit();
 }
 
-void Layer::SetFixedToContainerLayer(bool fixed_to_container_layer) {
-  if (fixed_to_container_layer_ == fixed_to_container_layer)
-    return;
-  fixed_to_container_layer_ = fixed_to_container_layer;
-  SetNeedsCommit();
+void Layer::SetPositionConstraint(const LayerPositionConstraint& constraint) {
+    if (position_constraint_ == constraint)
+        return;
+    position_constraint_ = constraint;
+    SetNeedsCommit();
 }
 
 void Layer::PushPropertiesTo(LayerImpl* layer) {
   layer->SetAnchorPoint(anchor_point_);
   layer->SetAnchorPointZ(anchor_point_z_);
   layer->SetBackgroundColor(background_color_);
   layer->SetBounds(bounds_);
   layer->SetContentBounds(content_bounds());
   layer->SetContentsScale(contents_scale_x(), contents_scale_y());
   layer->SetDebugName(debug_name_);
   layer->SetDoubleSided(double_sided_);
   layer->SetDrawCheckerboardForMissingTiles(
       draw_checkerboard_for_missing_tiles_);
   layer->SetForceRenderSurface(force_render_surface_);
   layer->SetDrawsContent(DrawsContent());
   layer->SetFilters(filters());
   layer->SetFilter(filter());
   layer->SetBackgroundFilters(background_filters());
   layer->SetMasksToBounds(masks_to_bounds_);
   layer->SetShouldScrollOnMainThread(should_scroll_on_main_thread_);
   layer->SetHaveWheelEventHandlers(have_wheel_event_handlers_);
   layer->SetNonFastScrollableRegion(non_fast_scrollable_region_);
   layer->SetTouchEventHandlerRegion(touch_event_handler_region_);
   layer->SetContentsOpaque(contents_opaque_);
   if (!layer->OpacityIsAnimatingOnImplOnly() && !OpacityIsAnimating())
     layer->SetOpacity(opacity_);
   DCHECK(!(OpacityIsAnimating() && layer->OpacityIsAnimatingOnImplOnly()));
   layer->SetPosition(position_);
   layer->SetIsContainerForFixedPositionLayers(
-      is_container_for_fixed_position_layers_);
-  layer->SetFixedToContainerLayer(fixed_to_container_layer_);
+      IsContainerForFixedPositionLayers());
+  layer->SetFixedContainerSizeDelta(gfx::Vector2dF());
+  layer->SetPositionConstraint(position_constraint_);
   layer->SetPreserves3d(preserves_3d());
   layer->SetUseParentBackfaceVisibility(use_parent_backface_visibility_);
   layer->SetSublayerTransform(sublayer_transform_);
   if (!layer->TransformIsAnimatingOnImplOnly() && !TransformIsAnimating())
     layer->SetTransform(transform_);
   DCHECK(!(TransformIsAnimating() && layer->TransformIsAnimatingOnImplOnly()));
 
   layer->SetScrollable(scrollable_);
   layer->SetScrollOffset(scroll_offset_);
   layer->SetMaxScrollOffset(max_scroll_offset_);
@@ skipping 218 matching lines @@
 
 ScrollbarLayer* Layer::ToScrollbarLayer() {
   return NULL;
 }
 
 RenderingStatsInstrumentation* Layer::rendering_stats_instrumentation() const {
   return layer_tree_host_->rendering_stats_instrumentation();
 }
 
 }  // namespace cc