Implement position: sticky updates on compositor

cc/trees/layer_tree_host_common_unittest.cc

 // Copyright 2011 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/trees/layer_tree_host_common.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <memory>
@@ skipping 6897 matching lines @@
   EXPECT_VECTOR2DF_EQ(expected_scroller_screen_space_transform_translation,
                       scroller_impl->ScreenSpaceTransform().To2dTranslation());
 
   gfx::Transform expected_scroll_child_screen_space_transform;
   expected_scroll_child_screen_space_transform.Translate(-5.3f, -9.3f);
   expected_scroll_child_screen_space_transform.RotateAboutYAxis(30);
   EXPECT_TRANSFORMATION_MATRIX_EQ(expected_scroll_child_screen_space_transform,
                                   scroll_child_impl->ScreenSpaceTransform());
 }
 
+TEST_F(LayerTreeHostCommonTest, StickyPosition) {
+  scoped_refptr<Layer> root = Layer::Create();
+  scoped_refptr<Layer> container = Layer::Create();
+  scoped_refptr<Layer> scroller = Layer::Create();
+  scoped_refptr<Layer> sticky_pos = Layer::Create();
+  root->AddChild(container);
+  container->AddChild(scroller);
+  scroller->AddChild(sticky_pos);
+  host()->SetRootLayer(root);
+  scroller->SetScrollClipLayerId(container->id());
+
+  LayerStickyPositionConstraint sticky_position;
+  sticky_position.is_sticky = true;
+  sticky_position.is_anchored_top = true;
+  sticky_position.top_offset = 10.0f;
+  sticky_position.absolute_sticky_box_rect = gfx::Rect(10, 20, 10, 10);
+  sticky_position.absolute_containing_block_rect = gfx::Rect(0, 0, 50, 50);

[ajuma, 2016/09/08 22:08:53]

Please also include tests that use the other sticky position constraint
settings, like is_anchored_bottom and left_offset.

[flackr, 2016/09/20 17:08:47]

Done.

+  sticky_pos->SetStickyPositionConstraint(sticky_position);
+
+  root->SetBounds(gfx::Size(100, 100));
+  container->SetBounds(gfx::Size(100, 100));
+  scroller->SetBounds(gfx::Size(1000, 1000));
+  sticky_pos->SetBounds(gfx::Size(10, 10));
+  sticky_pos->SetPosition(gfx::PointF(10, 20));
+
+  ExecuteCalculateDrawProperties(root.get());
+  host()->host_impl()->CreatePendingTree();
+  host()->CommitAndCreatePendingTree();
+  host()->host_impl()->ActivateSyncTree();
+  LayerTreeImpl* layer_tree_impl = host()->host_impl()->active_tree();
+
+  LayerImpl* root_impl = layer_tree_impl->LayerById(root->id());
+  LayerImpl* scroller_impl = layer_tree_impl->LayerById(scroller->id());
+  LayerImpl* sticky_pos_impl = layer_tree_impl->LayerById(sticky_pos->id());
+
+  ExecuteCalculateDrawProperties(root_impl);
+  EXPECT_VECTOR2DF_EQ(
+      gfx::Vector2dF(10.f, 20.f),
+      sticky_pos_impl->ScreenSpaceTransform().To2dTranslation());
+
+  // Scroll less than sticking point, sticky element should move with scroll as
+  // we haven't gotten to the initial sticky item location yet.
+  SetScrollOffsetDelta(scroller_impl, gfx::Vector2dF(5.f, 5.f));
+  ExecuteCalculateDrawProperties(root_impl);
+  EXPECT_VECTOR2DF_EQ(
+      gfx::Vector2dF(5.f, 15.f),
+      sticky_pos_impl->ScreenSpaceTransform().To2dTranslation());
+
+  // Scroll past the sticking point, the Y coordinate should now be clamped.
+  SetScrollOffsetDelta(scroller_impl, gfx::Vector2dF(15.f, 15.f));
+  ExecuteCalculateDrawProperties(root_impl);
+  EXPECT_VECTOR2DF_EQ(
+      gfx::Vector2dF(-5.f, 10.f),
+      sticky_pos_impl->ScreenSpaceTransform().To2dTranslation());
+  SetScrollOffsetDelta(scroller_impl, gfx::Vector2dF(15.f, 25.f));
+  ExecuteCalculateDrawProperties(root_impl);
+  EXPECT_VECTOR2DF_EQ(
+      gfx::Vector2dF(-5.f, 10.f),
+      sticky_pos_impl->ScreenSpaceTransform().To2dTranslation());
+
+  // Scroll past the end of the sticky container (note: this element does not
+  // have its own layer as it does not need to be composited).
+  SetScrollOffsetDelta(scroller_impl, gfx::Vector2dF(15.f, 50.f));
+  ExecuteCalculateDrawProperties(root_impl);
+  EXPECT_VECTOR2DF_EQ(
+      gfx::Vector2dF(-5.f, -10.f),
+      sticky_pos_impl->ScreenSpaceTransform().To2dTranslation());
+}
+
 TEST_F(LayerTreeHostCommonTest, NonFlatContainerForFixedPosLayer) {
   scoped_refptr<Layer> root = Layer::Create();
   scoped_refptr<Layer> container = Layer::Create();
   scoped_refptr<Layer> scroller = Layer::Create();
   scoped_refptr<Layer> fixed_pos = Layer::Create();
 
   scroller->SetIsContainerForFixedPositionLayers(true);
   root->AddChild(container);
   container->AddChild(scroller);
   scroller->AddChild(fixed_pos);
@@ skipping 2891 matching lines @@
   EXPECT_EQ(scroll_child6.id, grand_child10->scroll_tree_index());
   EXPECT_EQ(scroll_root1.id, parent3->scroll_tree_index());
   EXPECT_EQ(scroll_child7.id, child8->scroll_tree_index());
   EXPECT_EQ(scroll_root1.id, parent4->scroll_tree_index());
   EXPECT_EQ(scroll_root1.id, child9->scroll_tree_index());
   EXPECT_EQ(scroll_root1.id, grand_child12->scroll_tree_index());
 }
 
 }  // namespace
 }  // namespace cc