Handle nested position:sticky elements correctly (compositor)

cc/blink/web_layer_impl.cc

 // Copyright 2014 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/blink/web_layer_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <utility>
@@ skipping 360 matching lines @@
   web_constraint.leftOffset = constraint.left_offset;
   web_constraint.rightOffset = constraint.right_offset;
   web_constraint.topOffset = constraint.top_offset;
   web_constraint.bottomOffset = constraint.bottom_offset;
   web_constraint.parentRelativeStickyBoxOffset =
       constraint.parent_relative_sticky_box_offset;
   web_constraint.scrollContainerRelativeStickyBoxRect =
       constraint.scroll_container_relative_sticky_box_rect;
   web_constraint.scrollContainerRelativeContainingBlockRect =
       constraint.scroll_container_relative_containing_block_rect;
+  web_constraint.nearestLayerShiftingStickyBox =
+      constraint.nearest_layer_shifting_sticky_box;
+  web_constraint.nearestLayerShiftingContainingBlock =
+      constraint.nearest_layer_shifting_containing_block;
   return web_constraint;
 }
 static cc::LayerStickyPositionConstraint ToStickyPositionConstraint(
     const blink::WebLayerStickyPositionConstraint& web_constraint) {
   cc::LayerStickyPositionConstraint constraint;
   constraint.is_sticky = web_constraint.isSticky;
   constraint.is_anchored_left = web_constraint.isAnchoredLeft;
   constraint.is_anchored_right = web_constraint.isAnchoredRight;
   constraint.is_anchored_top = web_constraint.isAnchoredTop;
   constraint.is_anchored_bottom = web_constraint.isAnchoredBottom;
   constraint.left_offset = web_constraint.leftOffset;
   constraint.right_offset = web_constraint.rightOffset;
   constraint.top_offset = web_constraint.topOffset;
   constraint.bottom_offset = web_constraint.bottomOffset;
   constraint.parent_relative_sticky_box_offset =
       web_constraint.parentRelativeStickyBoxOffset;
   constraint.scroll_container_relative_sticky_box_rect =
       web_constraint.scrollContainerRelativeStickyBoxRect;
   constraint.scroll_container_relative_containing_block_rect =
       web_constraint.scrollContainerRelativeContainingBlockRect;
+  constraint.nearest_layer_shifting_sticky_box =
+      web_constraint.nearestLayerShiftingStickyBox;
+  constraint.nearest_layer_shifting_containing_block =
+      web_constraint.nearestLayerShiftingContainingBlock;

[chrishtr, 2017/03/21 22:18:28]

This seems unused.

[smcgruer, 2017/03/21 22:41:35]

It is used. See property_tree_builder.cc line 787, where this is used to
calculate nearest_node_shifting_containing_block, which is then used to get the
ancestor total to adjust the constraint rect.

[chrishtr, 2017/03/21 23:26:05]

I see, sorry.

It seems weird to me to expose a "containing block" name to cc. cc shouldn't
have to care about
containing blocks. More comments below.

   return constraint;
 }
 void WebLayerImpl::setStickyPositionConstraint(
     const blink::WebLayerStickyPositionConstraint& constraint) {
   layer_->SetStickyPositionConstraint(ToStickyPositionConstraint(constraint));
 }
 blink::WebLayerStickyPositionConstraint WebLayerImpl::stickyPositionConstraint()
     const {
   return ToWebLayerStickyPositionConstraint(
       layer_->sticky_position_constraint());
@@ skipping 58 matching lines @@
 
 void WebLayerImpl::SetContentsOpaqueIsFixed(bool fixed) {
   contents_opaque_is_fixed_ = fixed;
 }
 
 void WebLayerImpl::setHasWillChangeTransformHint(bool has_will_change) {
   layer_->SetHasWillChangeTransformHint(has_will_change);
 }
 
 }  // namespace cc_blink