Properly calculate the localBounds for elements with overflow clipped

third_party/WebKit/Source/core/layout/ScrollAnchorTest.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/ScrollAnchor.h"
 
 #include "core/dom/ClientRect.h"
 #include "core/frame/VisualViewport.h"
 #include "core/layout/LayoutBox.h"
 #include "core/layout/LayoutTestHelper.h"
@@ skipping 137 matching lines @@
     setHeight(document().getElementById("div"), 100);
     EXPECT_EQ(document().getElementById("text")->layoutObject(),
         scrollAnchor(lViewport).anchorObject());
     EXPECT_EQ(top, vViewport.scrollPosition().y());
 
     // Scrolling the visual viewport should clear the anchor.
     vViewport.setLocation(FloatPoint(0, 0));
     EXPECT_EQ(nullptr, scrollAnchor(lViewport).anchorObject());
 }
 
+// Test that we don't descend into elements that clip overflow content since we

[skobes, 2016/07/11 21:25:03]

nit: it's not that we will never descend into them, rather that we ignore the
clipped content when computing visibility.

[ymalik, 2016/07/11 21:35:34]

Done!

+// may end up with an anchor that we think is in the viewport but is really not.
+TEST_F(ScrollAnchorTest, ClippedScrollersSkipped)
+{
+    setBodyInnerHTML(
+        "<style>"
+        "    body { height: 2000px; }"
+        "    #scroller { overflow: scroll; width: 500px; height: 300px; }"
+        "    .anchor {"
+        "         position:relative; height: 100px; width: 150px;"
+        "         background-color: #afa; border: 1px solid gray;"
+        "    }"
+        "    #forceScrolling { height: 500px; background-color: #fcc; }"
+        "</style>"
+        "<div id='scroller'>"
+        "    <div id='innerChanger'></div>"
+        "    <div id='innerAnchor' class='anchor'></div>"
+        "    <div id='forceScrolling'></div>"
+        "</div>"
+        "<div id='outerChanger'></div>"
+        "<div id='outerAnchor' class='anchor'></div>");
+
+    ScrollableArea* scroller = scrollerForElement(document().getElementById("scroller"));
+    ScrollableArea* viewport = layoutViewport();
+
+    document().getElementById("scroller")->setScrollTop(100);
+    scrollLayoutViewport(DoubleSize(0, 350));
+
+    setHeight(document().getElementById("innerChanger"), 200);
+    setHeight(document().getElementById("outerChanger"), 150);
+
+    EXPECT_EQ(300, scroller->scrollPosition().y());
+    EXPECT_EQ(document().getElementById("innerAnchor")->layoutObject(),
+        scrollAnchor(scroller).anchorObject());
+    EXPECT_EQ(500, viewport->scrollPosition().y());
+    EXPECT_EQ(document().getElementById("outerAnchor")->layoutObject(),
+        scrollAnchor(viewport).anchorObject());
+}
+
 TEST_F(ScrollAnchorTest, FractionalOffsetsAreRoundedBeforeComparing)
 {
     setBodyInnerHTML(
         "<style> body { height: 1000px } </style>"
         "<div id='block1' style='height: 50.4px'>abc</div>"
         "<div id='block2' style='height: 100px'>def</div>");
 
     ScrollableArea* viewport = layoutViewport();
     scrollLayoutViewport(DoubleSize(0, 100));
 
@@ skipping 443 matching lines @@
         "<div id=c></div>"
         "<div id=d></div>");
 
     checkCorner("b", Corner::TopRight, DoublePoint(-20,  20),  DoubleSize(0, 0));
     checkCorner("a", Corner::TopRight, DoublePoint(-420, 20),  DoubleSize(400, 0));
     checkCorner("d", Corner::TopRight, DoublePoint(-20,  320), DoubleSize(0, -300));
     checkCorner("c", Corner::TopRight, DoublePoint(-420, 320), DoubleSize(400, -300));
 }
 
 }