Add background attachment fixed main thread scrolling reason [spv2]

third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp

Index: third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp
index 9b0078b2988c83d2c87d32eee6253cc5e495c07c..dfda5678ef2018e2f3ff54e2bc14a913e3de35e6 100644
--- a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp
@@ -2009,4 +2009,103 @@ TEST_P(PaintPropertyTreeBuilderTest, SVGRootNoClip)
     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