Add background attachment fixed main thread scrolling reason [spv2]

third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.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/layout/LayoutTestHelper.h"
 #include "core/layout/LayoutTreeAsText.h"
 #include "core/layout/api/LayoutViewItem.h"
 #include "core/paint/ObjectPaintProperties.h"
 #include "core/paint/PaintPropertyTreePrinter.h"
 #include "platform/graphics/paint/GeometryMapper.h"
@@ skipping 1991 matching lines @@
 TEST_P(PaintPropertyTreeBuilderTest, SVGRootNoClip)
 {
     setBodyInnerHTML(
         "<svg id='svg' xmlns='http://www.w3.org/2000/svg' width='100px' height='100px' style='overflow: visible'>"
         "  <rect width='200' height='200' fill='red' />"
         "</svg>");
 
     EXPECT_FALSE(getLayoutObjectByElementId("svg")->objectPaintProperties()->overflowClip());
 }
 
+TEST_P(PaintPropertyTreeBuilderTest, MainThreadScrollReasonsWithNestedScrollers)
+{
+    setBodyInnerHTML(
+        "<style>"
+        "  #overflowA {"
+        "    position: absolute;"
+        "    overflow: scroll;"
+        "    width: 20px;"
+        "    height: 20px;"
+        "  }"
+        "  #overflowB {"
+        "    position: absolute;"
+        "    overflow: scroll;"
+        "    width: 5px;"
+        "    height: 3px;"
+        "  }"
+        "  .backgroundAttachmentFixed {"
+        "    background-image: url('foo');"
+        "    background-attachment: fixed;"
+        "  }"
+        "  .forceScroll {"
+        "    height: 4000px;"
+        "  }"
+        "</style>"
+        "<div id='overflowA'>"
+        "  <div id='overflowB' class='backgroundAttachmentFixed'>"
+        "    <div class='forceScroll'></div>"
+        "  </div>"
+        "  <div class='forceScroll'></div>"
+        "</div>"
+        "<div class='forceScroll'></div>");
+    Element* overflowA = document().getElementById("overflowA");
+    Element* overflowB = document().getElementById("overflowB");
+
+    EXPECT_TRUE(frameScroll()->hasBackgroundAttachmentFixedMainThreadScrollingReason());
+    EXPECT_TRUE(overflowA->layoutObject()->objectPaintProperties()->scroll()->hasBackgroundAttachmentFixedMainThreadScrollingReason());
+    EXPECT_FALSE(overflowB->layoutObject()->objectPaintProperties()->scroll()->hasBackgroundAttachmentFixedMainThreadScrollingReason());

[ajuma, 2016/09/19 14:38:02]

Should overflowB also have a main-thread scrolling reason?

[pdr., 2016/09/19 20:25:50]

Good question! The background of overflowB is painted using the parent's
(overflowA) scroll node and scroll offset transform because they are not
affected by overflowB's scroll position. For this reason, we actually don't set
the main thread reason on overflowB, just the parent space where the background
is painted.

Another way of looking at this is through the transform tree for overflowB:
[ paintOffsetTranslation ]
|
+---[ transform ] < background painted here
    |
    +---[ perspective ]
        |
        +---[ scrollTranslation ] < scroll context setup here

+
+    // Removing a main thread scrolling reason should update the entire tree.
+    overflowB->removeAttribute("class");
+    document().view()->updateAllLifecyclePhases();
+    EXPECT_FALSE(frameScroll()->hasBackgroundAttachmentFixedMainThreadScrollingReason());
+    EXPECT_FALSE(overflowA->layoutObject()->objectPaintProperties()->scroll()->hasBackgroundAttachmentFixedMainThreadScrollingReason());
+    EXPECT_FALSE(overflowB->layoutObject()->objectPaintProperties()->scroll()->hasBackgroundAttachmentFixedMainThreadScrollingReason());
+
+    // Adding a main thread scrolling reason should update the entire tree.
+    overflowB->setAttribute(HTMLNames::classAttr, "backgroundAttachmentFixed");
+    document().view()->updateAllLifecyclePhases();
+    EXPECT_TRUE(frameScroll()->hasBackgroundAttachmentFixedMainThreadScrollingReason());
+    EXPECT_TRUE(overflowA->layoutObject()->objectPaintProperties()->scroll()->hasBackgroundAttachmentFixedMainThreadScrollingReason());
+    EXPECT_FALSE(overflowB->layoutObject()->objectPaintProperties()->scroll()->hasBackgroundAttachmentFixedMainThreadScrollingReason());
+}
+
+TEST_P(PaintPropertyTreeBuilderTest, MainThreadScrollReasonsWithFixedScroller)
+{
+    setBodyInnerHTML(
+        "<style>"
+        "  #overflowA {"
+        "    position: absolute;"
+        "    overflow: scroll;"
+        "    width: 20px;"
+        "    height: 20px;"
+        "  }"
+        "  #overflowB {"
+        "    position: fixed;"
+        "    overflow: scroll;"
+        "    width: 5px;"
+        "    height: 3px;"
+        "  }"
+        "  .backgroundAttachmentFixed {"
+        "    background-image: url('foo');"
+        "    background-attachment: fixed;"
+        "  }"
+        "  .forceScroll {"
+        "    height: 4000px;"
+        "  }"
+        "</style>"
+        "<div id='overflowA'>"
+        "  <div id='overflowB' class='backgroundAttachmentFixed'>"
+        "    <div class='forceScroll'></div>"
+        "  </div>"
+        "  <div class='forceScroll'></div>"
+        "</div>"
+        "<div class='forceScroll'></div>");
+    Element* overflowA = document().getElementById("overflowA");
+    Element* overflowB = document().getElementById("overflowB");
+
+    EXPECT_TRUE(rootScroll()->hasBackgroundAttachmentFixedMainThreadScrollingReason());
+    EXPECT_FALSE(overflowA->layoutObject()->objectPaintProperties()->scroll()->hasBackgroundAttachmentFixedMainThreadScrollingReason());
+    EXPECT_FALSE(overflowB->layoutObject()->objectPaintProperties()->scroll()->hasBackgroundAttachmentFixedMainThreadScrollingReason());
+
+    // Removing a main thread scrolling reason should update the entire tree.
+    overflowB->removeAttribute("class");
+    document().view()->updateAllLifecyclePhases();
+    EXPECT_FALSE(rootScroll()->hasBackgroundAttachmentFixedMainThreadScrollingReason());
+    EXPECT_FALSE(overflowA->layoutObject()->objectPaintProperties()->scroll()->hasBackgroundAttachmentFixedMainThreadScrollingReason());
+    EXPECT_FALSE(overflowB->layoutObject()->objectPaintProperties()->scroll()->hasBackgroundAttachmentFixedMainThreadScrollingReason());
+}
+
 } // namespace blink