Only promote fixed position elements on low dpi without transform or opacity.

third_party/WebKit/Source/core/layout/compositing/CompositingReasonFinderTest.cpp

Index: third_party/WebKit/Source/core/layout/compositing/CompositingReasonFinderTest.cpp
diff --git a/third_party/WebKit/Source/core/layout/compositing/CompositingReasonFinderTest.cpp b/third_party/WebKit/Source/core/layout/compositing/CompositingReasonFinderTest.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..7fec9f6512b72d9c3358105d650d1aa8c21c6c74
--- /dev/null
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositingReasonFinderTest.cpp
@@ -0,0 +1,162 @@
+// Copyright 2016 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/layout/compositing/CompositingReasonFinder.h"
+
+#include "core/frame/FrameView.h"
+#include "core/layout/LayoutBlock.h"
+#include "core/layout/LayoutTestHelper.h"
+#include "core/paint/PaintLayer.h"
+#include "platform/graphics/GraphicsLayer.h"
+#include "platform/scroll/ScrollTypes.h"
+#include "platform/testing/RuntimeEnabledFeaturesTestHelpers.h"
+
+namespace blink {
+
+class CompositingReasonFinderTest : public RenderingTest {
+ public:
+  CompositingReasonFinderTest()
+      : RenderingTest(SingleChildFrameLoaderClient::create()) {}
+
+ private:
+  void SetUp() override {
+    RenderingTest::SetUp();
+    enableCompositing();
+  }
+};
+
+TEST_F(CompositingReasonFinderTest, PromoteOpaqueFixedPosition) {
+  ScopedCompositeFixedPositionForTest compositeFixedPosition(true);
+
+  setBodyInnerHTML(
+      "<div id='translucent' style='width: 20px; height: 20px; position: "
+      "fixed; top: 100px; left: 100px;'></div>"
+      "<div id='opaque' style='width: 20px; height: 20px; position: fixed; "
+      "top: 100px; left: 200px; background: white;'></div>"
+      "<div id='opaque-with-shadow' style='width: 20px; height: 20px; "
+      "position: fixed; top: 100px; left: 300px; background: white; "
+      "box-shadow: 10px 10px 5px #888888;'></div>"
+      "<div id='spacer' style='height: 2000px'></div>");
+
+  document().view()->updateAllLifecyclePhases();
+
+  // The translucent fixed box should not be promoted.
+  Element* element = document().getElementById("translucent");
+  PaintLayer* paintLayer =
+      toLayoutBoxModelObject(element->layoutObject())->layer();
+  EXPECT_EQ(NotComposited, paintLayer->compositingState());
+
+  // The opaque fixed box should be promoted and be opaque so that text will be
+  // drawn with subpixel anti-aliasing.
+  element = document().getElementById("opaque");
+  paintLayer = toLayoutBoxModelObject(element->layoutObject())->layer();
+  EXPECT_EQ(PaintsIntoOwnBacking, paintLayer->compositingState());
+  EXPECT_TRUE(paintLayer->graphicsLayerBacking()->contentsOpaque());
+
+  // The opaque fixed box with shadow should not be promoted because the layer
+  // will include the shadow which is not opaque.
+  element = document().getElementById("opaque-with-shadow");
+  paintLayer = toLayoutBoxModelObject(element->layoutObject())->layer();
+  EXPECT_EQ(NotComposited, paintLayer->compositingState());
+}
+
+// Tests that a transform on the fixed or an ancestor will prevent promotion
+// TODO(flackr): Allow integer transforms as long as all of the ancestor
+// transforms are also integer.
+TEST_F(CompositingReasonFinderTest, OnlyNonTransformedFixedLayersPromoted) {
+  ScopedCompositeFixedPositionForTest compositeFixedPosition(true);
+
+  setBodyInnerHTML(
+      "<style>"
+      "#fixed { position: fixed; height: 200px; width: 200px; background: "
+      "white; top: 0; }"
+      "#spacer { height: 3000px; }"
+      "</style>"
+      "<div id=\"parent\">"
+      "  <div id=\"fixed\"></div>"
+      "  <div id=\"spacer\"></div>"
+      "</div>");
+  document().view()->updateAllLifecyclePhases();
+
+  EXPECT_TRUE(RuntimeEnabledFeatures::compositeOpaqueScrollersEnabled());
+  Element* parent = document().getElementById("parent");
+  Element* fixed = document().getElementById("fixed");
+  PaintLayer* paintLayer =
+      toLayoutBoxModelObject(fixed->layoutObject())->layer();
+  ASSERT_TRUE(paintLayer);
+  EXPECT_EQ(PaintsIntoOwnBacking, paintLayer->compositingState());
+  EXPECT_TRUE(paintLayer->graphicsLayerBacking()->contentsOpaque());
+
+  // Change the parent to have a transform.
+  parent->setAttribute(HTMLNames::styleAttr, "transform: translate(1px, 0);");
+  document().view()->updateAllLifecyclePhases();
+  paintLayer = toLayoutBoxModelObject(fixed->layoutObject())->layer();
+  ASSERT_TRUE(paintLayer);
+  EXPECT_EQ(NotComposited, paintLayer->compositingState());
+
+  // Change the parent to have no transform again.
+  parent->removeAttribute(HTMLNames::styleAttr);
+  document().view()->updateAllLifecyclePhases();
+  paintLayer = toLayoutBoxModelObject(fixed->layoutObject())->layer();
+  ASSERT_TRUE(paintLayer);
+  EXPECT_EQ(PaintsIntoOwnBacking, paintLayer->compositingState());
+  EXPECT_TRUE(paintLayer->graphicsLayerBacking()->contentsOpaque());
+
+  // Apply a transform to the fixed directly.
+  fixed->setAttribute(HTMLNames::styleAttr, "transform: translate(1px, 0);");
+  document().view()->updateAllLifecyclePhases();
+  paintLayer = toLayoutBoxModelObject(fixed->layoutObject())->layer();
+  ASSERT_TRUE(paintLayer);
+  EXPECT_EQ(NotComposited, paintLayer->compositingState());
+}
+
+// Test that opacity applied to the fixed or an ancestor will cause the
+// scrolling contents layer to not be promoted.
+TEST_F(CompositingReasonFinderTest, OnlyOpaqueFixedLayersPromoted) {
+  ScopedCompositeFixedPositionForTest compositeFixedPosition(true);
+
+  setBodyInnerHTML(
+      "<style>"
+      "#fixed { position: fixed; height: 200px; width: 200px; background: "
+      "white; top: 0}"
+      "#spacer { height: 3000px; }"
+      "</style>"
+      "<div id=\"parent\">"
+      "  <div id=\"fixed\"></div>"
+      "  <div id=\"spacer\"></div>"
+      "</div>");
+  document().view()->updateAllLifecyclePhases();
+
+  EXPECT_TRUE(RuntimeEnabledFeatures::compositeOpaqueScrollersEnabled());
+  Element* parent = document().getElementById("parent");
+  Element* fixed = document().getElementById("fixed");
+  PaintLayer* paintLayer =
+      toLayoutBoxModelObject(fixed->layoutObject())->layer();
+  ASSERT_TRUE(paintLayer);
+  EXPECT_EQ(PaintsIntoOwnBacking, paintLayer->compositingState());
+  EXPECT_TRUE(paintLayer->graphicsLayerBacking()->contentsOpaque());
+
+  // Change the parent to be partially translucent.
+  parent->setAttribute(HTMLNames::styleAttr, "opacity: 0.5;");
+  document().view()->updateAllLifecyclePhases();
+  paintLayer = toLayoutBoxModelObject(fixed->layoutObject())->layer();
+  ASSERT_TRUE(paintLayer);
+  EXPECT_EQ(NotComposited, paintLayer->compositingState());
+
+  // Change the parent to be opaque again.
+  parent->setAttribute(HTMLNames::styleAttr, "opacity: 1;");
+  document().view()->updateAllLifecyclePhases();
+  paintLayer = toLayoutBoxModelObject(fixed->layoutObject())->layer();
+  ASSERT_TRUE(paintLayer);
+  EXPECT_EQ(PaintsIntoOwnBacking, paintLayer->compositingState());
+  EXPECT_TRUE(paintLayer->graphicsLayerBacking()->contentsOpaque());
+
+  // Make the fixed translucent.
+  fixed->setAttribute(HTMLNames::styleAttr, "opacity: 0.5");
+  document().view()->updateAllLifecyclePhases();
+  paintLayer = toLayoutBoxModelObject(fixed->layoutObject())->layer();
+  ASSERT_TRUE(paintLayer);
+  EXPECT_EQ(NotComposited, paintLayer->compositingState());
+}
+}