Handle nested position:sticky elements correctly (compositor)

cc/trees/draw_property_utils_unittest.cc

Index: cc/trees/draw_property_utils_unittest.cc
diff --git a/cc/trees/draw_property_utils_unittest.cc b/cc/trees/draw_property_utils_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..96c7e6683fc73da3f10a4dfe13f7c1a2448c86b5
--- /dev/null
+++ b/cc/trees/draw_property_utils_unittest.cc
@@ -0,0 +1,205 @@
+// Copyright 2017 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/draw_property_utils.h"
+
+#include <stddef.h>
+
+#include "base/memory/ref_counted.h"
+#include "cc/layers/layer.h"
+#include "cc/layers/layer_sticky_position_constraint.h"
+#include "cc/test/geometry_test_utils.h"
+#include "cc/test/layer_test_common.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace cc {
+namespace draw_property_utils {
+
+namespace {
+class DrawPropertyUtilsTest : public LayerTestCommon::LayerImplTest,
+                              public testing::Test {};
+}  // namespace
+
+TEST_F(DrawPropertyUtilsTest, CalculateTotalStickyOffsetToScroller) {
+  scoped_refptr<Layer> root = Layer::Create();
+  scoped_refptr<Layer> container = Layer::Create();
+  scoped_refptr<Layer> scroller = Layer::Create();
+  scoped_refptr<Layer> child_sticky = Layer::Create();
+  scoped_refptr<Layer> grandchild_sticky = Layer::Create();
+  scoped_refptr<Layer> great_grandchild_layer = Layer::Create();
+
+  root->AddChild(container);
+  container->AddChild(scroller);
+  scroller->AddChild(child_sticky);
+  child_sticky->AddChild(grandchild_sticky);
+  grandchild_sticky->AddChild(great_grandchild_layer);
+
+  host()->SetRootLayer(root);
+  scroller->SetScrollClipLayerId(container->id());
+
+  LayerStickyPositionConstraint child_sticky_pos;
+  child_sticky_pos.is_sticky = true;
+  child_sticky_pos.local_sticky_offset = gfx::Vector2dF(10, 50);
+  child_sticky->SetStickyPositionConstraint(child_sticky_pos);
+
+  LayerStickyPositionConstraint grandchild_sticky_pos;
+  grandchild_sticky_pos.is_sticky = true;
+  grandchild_sticky_pos.nearest_layer_shifting_containing_block =
+      child_sticky.get();
+  grandchild_sticky_pos.local_sticky_offset = gfx::Vector2dF(100, 0);
+  grandchild_sticky->SetStickyPositionConstraint(grandchild_sticky_pos);
+
+  host()->host_impl()->CreatePendingTree();
+  host()->CommitAndCreatePendingTree();
+  host()->host_impl()->ActivateSyncTree();
+
+  gfx::Vector2dF offset =
+      CalculateTotalStickyOffsetToScroller(child_sticky.get(), scroller->id());
+  EXPECT_VECTOR2DF_EQ(gfx::Vector2dF(10, 50), offset);
+
+  offset = CalculateTotalStickyOffsetToScroller(grandchild_sticky.get(),
+                                                scroller->id());
+  EXPECT_VECTOR2DF_EQ(gfx::Vector2dF(110, 50), offset);
+
+  // The great grandchild, although not sticky itself, should be able to locate
+  // its nearest sticky ancestor and walk up from there.
+  offset = CalculateTotalStickyOffsetToScroller(great_grandchild_layer.get(),
+                                                scroller->id());
+  EXPECT_VECTOR2DF_EQ(gfx::Vector2dF(110, 50), offset);
+}
+
+TEST_F(DrawPropertyUtilsTest, CalculateTotalStickyOffsetToScrollerComplex) {
+  scoped_refptr<Layer> root = Layer::Create();
+  scoped_refptr<Layer> container = Layer::Create();
+  scoped_refptr<Layer> scroller = Layer::Create();
+  scoped_refptr<Layer> child_sticky = Layer::Create();
+  scoped_refptr<Layer> grandchild_sticky = Layer::Create();
+  scoped_refptr<Layer> great_grandchild_sticky = Layer::Create();
+
+  root->AddChild(container);
+  container->AddChild(scroller);
+  scroller->AddChild(child_sticky);
+  child_sticky->AddChild(grandchild_sticky);
+  grandchild_sticky->AddChild(great_grandchild_sticky);
+
+  host()->SetRootLayer(root);
+  scroller->SetScrollClipLayerId(container->id());
+
+  LayerStickyPositionConstraint child_sticky_pos;
+  child_sticky_pos.is_sticky = true;
+  child_sticky_pos.local_sticky_offset = gfx::Vector2dF(10, 50);
+  child_sticky->SetStickyPositionConstraint(child_sticky_pos);
+
+  LayerStickyPositionConstraint grandchild_sticky_pos;
+  grandchild_sticky_pos.is_sticky = true;
+  grandchild_sticky_pos.nearest_layer_shifting_containing_block =
+      child_sticky.get();
+  grandchild_sticky_pos.local_sticky_offset = gfx::Vector2dF(100, 0);
+  grandchild_sticky->SetStickyPositionConstraint(grandchild_sticky_pos);
+
+  // We are considering the grandchild to be something like an inline element
+  // that doesn't become a containing block for the great-grandchild. Therefore,
+  // the great-grandchild points at both the child and grandchild, but should
+  // accumulate both (via the grandchild) in the walk.
+  LayerStickyPositionConstraint great_grandchild_sticky_pos;
+  great_grandchild_sticky_pos.is_sticky = true;
+  great_grandchild_sticky_pos.local_sticky_offset = gfx::Vector2dF(0, 20);
+  great_grandchild_sticky_pos.nearest_layer_shifting_sticky_box =
+      grandchild_sticky.get();
+  great_grandchild_sticky_pos.nearest_layer_shifting_containing_block =
+      child_sticky.get();
+  great_grandchild_sticky->SetStickyPositionConstraint(
+      great_grandchild_sticky_pos);
+
+  host()->host_impl()->CreatePendingTree();
+  host()->CommitAndCreatePendingTree();
+  host()->host_impl()->ActivateSyncTree();
+
+  gfx::Vector2dF offset =
+      CalculateTotalStickyOffsetToScroller(child_sticky.get(), scroller->id());
+  EXPECT_VECTOR2DF_EQ(gfx::Vector2dF(10, 50), offset);
+
+  offset = CalculateTotalStickyOffsetToScroller(grandchild_sticky.get(),
+                                                scroller->id());
+  EXPECT_VECTOR2DF_EQ(gfx::Vector2dF(110, 50), offset);
+
+  offset = CalculateTotalStickyOffsetToScroller(great_grandchild_sticky.get(),
+                                                scroller->id());
+  EXPECT_VECTOR2DF_EQ(gfx::Vector2dF(110, 70), offset);
+}
+
+TEST_F(DrawPropertyUtilsTest,
+       CalculateTotalStickyOffsetToScrollerNoStickyLayers) {
+  scoped_refptr<Layer> root = Layer::Create();
+  scoped_refptr<Layer> container = Layer::Create();
+  scoped_refptr<Layer> other_container = Layer::Create();
+  scoped_refptr<Layer> scroller = Layer::Create();
+  scoped_refptr<Layer> first_child = Layer::Create();
+  scoped_refptr<Layer> second_child = Layer::Create();
+  scoped_refptr<Layer> first_grandchild = Layer::Create();
+
+  root->AddChild(container);
+  root->AddChild(other_container);
+  container->AddChild(scroller);
+  scroller->AddChild(first_child);
+  scroller->AddChild(second_child);
+  first_child->AddChild(first_grandchild);
+
+  host()->SetRootLayer(root);
+  scroller->SetScrollClipLayerId(container->id());
+
+  LayerStickyPositionConstraint sticky_position;
+  sticky_position.is_sticky = true;
+  sticky_position.local_sticky_offset = gfx::Vector2dF(10, 50);
+  second_child->SetStickyPositionConstraint(sticky_position);
+
+  host()->host_impl()->CreatePendingTree();
+  host()->CommitAndCreatePendingTree();
+  host()->host_impl()->ActivateSyncTree();
+
+  // We should ignore second_child, as it is not between us and the scroller.
+  gfx::Vector2dF offset = CalculateTotalStickyOffsetToScroller(
+      first_grandchild.get(), scroller->id());
+  EXPECT_VECTOR2DF_EQ(gfx::Vector2dF(0, 0), offset);
+
+  // There is no scroller above other_container, so its offset is zero.
+  offset = CalculateTotalStickyOffsetToScroller(other_container.get(), -1);
+  EXPECT_VECTOR2DF_EQ(gfx::Vector2dF(0, 0), offset);
+}
+
+TEST_F(DrawPropertyUtilsTest,
+       CalculateTotalStickyOffsetToScrollerNoStickyLayersBelowScroller) {
+  scoped_refptr<Layer> root = Layer::Create();
+  scoped_refptr<Layer> sticky = Layer::Create();
+  scoped_refptr<Layer> container = Layer::Create();
+  scoped_refptr<Layer> scroller = Layer::Create();
+  scoped_refptr<Layer> first_child = Layer::Create();
+  scoped_refptr<Layer> first_grandchild = Layer::Create();
+
+  root->AddChild(sticky);
+  sticky->AddChild(container);
+  container->AddChild(scroller);
+  scroller->AddChild(first_child);
+  first_child->AddChild(first_grandchild);
+
+  host()->SetRootLayer(root);
+  scroller->SetScrollClipLayerId(container->id());
+
+  LayerStickyPositionConstraint sticky_position;
+  sticky_position.is_sticky = true;
+  sticky_position.local_sticky_offset = gfx::Vector2dF(10, 50);
+  sticky->SetStickyPositionConstraint(sticky_position);
+
+  host()->host_impl()->CreatePendingTree();
+  host()->CommitAndCreatePendingTree();
+  host()->host_impl()->ActivateSyncTree();
+
+  // We should ignore the sticky element above the scroller.
+  gfx::Vector2dF offset = CalculateTotalStickyOffsetToScroller(
+      first_grandchild.get(), scroller->id());
+  EXPECT_VECTOR2DF_EQ(gfx::Vector2dF(0, 0), offset);
+}
+
+}  // namespace draw_property_utils
+}  // namespace cc