Mark elements as viewport constrained when they become sticky positioned

third_party/WebKit/Source/core/frame/FrameViewTest.cpp

 // Copyright 2015 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 "core/frame/FrameView.h"
 
+#include <memory>
+
 #include "bindings/core/v8/ExceptionState.h"
 #include "core/frame/Settings.h"
 #include "core/html/HTMLElement.h"
+#include "core/layout/LayoutBoxModelObject.h"
 #include "core/layout/LayoutObject.h"
 #include "core/loader/EmptyClients.h"
 #include "core/page/Page.h"
 #include "core/testing/DummyPageHolder.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/geometry/IntSize.h"
 #include "platform/graphics/paint/PaintArtifact.h"
 #include "platform/heap/Handle.h"
 #include "platform/testing/RuntimeEnabledFeaturesTestHelpers.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
-#include <memory>
 
 using testing::_;
 using testing::AnyNumber;
 
 namespace blink {
 namespace {
 
 class MockChromeClient : public EmptyChromeClient {
  public:
   MockChromeClient() : m_hasScheduledAnimation(false) {}
@@ skipping 98 matching lines @@
 
 // NoOverflowInIncrementVisuallyNonEmptyPixelCount tests fail if the number of
 // pixels is calculated in 32-bit integer, because 65536 * 65536 would become 0
 // if it was calculated in 32-bit and thus it would be considered as empty.
 TEST_P(FrameViewTest, NoOverflowInIncrementVisuallyNonEmptyPixelCount) {
   EXPECT_FALSE(document().view()->isVisuallyNonEmpty());
   document().view()->incrementVisuallyNonEmptyPixelCount(IntSize(65536, 65536));
   EXPECT_TRUE(document().view()->isVisuallyNonEmpty());
 }
 
+TEST_P(FrameViewTest, StyleChangeUpdatesViewportConstrainedObjects) {
+  // When using root layer scrolling there is no concept of viewport constrained
+  // objects, so skip this test.
+  if (RuntimeEnabledFeatures::rootLayerScrollingEnabled())
+    return;
+
+  document().body()->setInnerHTML(
+      "<style>.container { height: 200%; }"
+      "#sticky { position: sticky; top: 0; height: 50px; }</style>"
+      "<div class='container'><div id='sticky'></div></div>");
+  document().view()->updateAllLifecyclePhases();
+
+  LayoutBoxModelObject* sticky = toLayoutBoxModelObject(
+      document().getElementById("sticky")->layoutObject());
+
+  EXPECT_TRUE(
+      document().view()->viewportConstrainedObjects()->contains(sticky));
+
+  // Making the element non-sticky should remove it from the set of
+  // viewport-constrained objects.
+  document().getElementById("sticky")->setAttribute(HTMLNames::styleAttr,
+                                                    "position: relative");
+  document().view()->updateAllLifecyclePhases();
+
+  EXPECT_FALSE(
+      document().view()->viewportConstrainedObjects()->contains(sticky));
+
+  // And making it sticky again should put it back in that list.
+  document().getElementById("sticky")->setAttribute(HTMLNames::styleAttr, "");
+  document().view()->updateAllLifecyclePhases();
+
+  EXPECT_TRUE(
+      document().view()->viewportConstrainedObjects()->contains(sticky));
+}
+
 }  // namespace
 }  // namespace blink