Round visual rects when crossing frame boundaries.

third_party/WebKit/Source/core/layout/LayoutObjectTest.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/LayoutObject.h"
 
 #include "core/layout/LayoutTestHelper.h"
 #include "core/layout/LayoutView.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 163 matching lines @@
     frameDocument.view()->setScrollPosition(DoublePoint(0, 47), ProgrammaticScroll);
     LayoutRect rect(4, 60, 20, 80);
     EXPECT_TRUE(frameText->mapToVisibleRectInAncestorSpace(frameContainer, rect));
     EXPECT_EQ(rect, LayoutRect(4, 13, 20, 37));
 
     rect = LayoutRect(4, 60, 0, 80);
     EXPECT_TRUE(frameText->mapToVisibleRectInAncestorSpace(frameContainer, rect, EdgeInclusive));
     EXPECT_EQ(rect, LayoutRect(4, 13, 0, 37));
 }
 
+TEST_F(LayoutObjectTest, LayoutViewMapToVisibleRectInAncestorSpaceSubpixelRounding)
+{
+    document().setBaseURLOverride(KURL(ParsedURLString, "http://test.com"));
+    setBodyInnerHTML(
+        "<style>body { margin: 0; }</style>"
+        "<div id=frameContainer style='position: relative; left: 0.5px'>"
+        "  <iframe id=frame style='position: relative; left: 0.5px' src='http://test.com' width='200' height='200' frameBorder='0'></iframe>"
+        "</div>");
+
+    Document& frameDocument = setupChildIframe(
+        "frame", "<style>body { margin: 0; }</style><div id='target' style='position: relative; width: 100px; height: 100px; left: 0.5px'>");
+    frameDocument.updateLayout();
+
+    LayoutBlock* frameContainer = toLayoutBlock(getLayoutObjectByElementId("frameContainer"));
+    LayoutObject* target = frameDocument.getElementById("target")->layoutObject();
+    LayoutRect rect(0, 0, 100, 100);
+    EXPECT_TRUE(target->mapToVisibleRectInAncestorSpace(frameContainer, rect));
+    // When passing from the iframe to the parent frame, the rect of (0.5, 0, 100, 100) is expanded to (0, 0, 100, 100), and then offset by
+    // the 0.5 offset of frameContainer.
+    EXPECT_EQ(LayoutRect(LayoutPoint(DoublePoint(0.5, 0)), LayoutSize(101, 100)), rect);
+}
+
 } // namespace blink