Make column snapping optional when translating to flow thread coordinates.

third_party/WebKit/Source/core/layout/MapCoordinatesTest.cpp

 // 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/LayoutInline.h"
 #include "core/layout/LayoutTestHelper.h"
 #include "core/layout/LayoutView.h"
 #include "platform/geometry/TransformState.h"
 #include "platform/testing/RuntimeEnabledFeaturesTestHelpers.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 837 matching lines @@
   EXPECT_EQ(FloatPoint(10, 120), mappedPoint);
   mappedPoint = mapAncestorToLocal(target, flowThread, mappedPoint);
   EXPECT_EQ(FloatPoint(), mappedPoint);
 
   mappedPoint = mapLocalToAncestor(flowThread, container, FloatPoint(10, 120));
   EXPECT_EQ(FloatPoint(125, 35), mappedPoint);
   mappedPoint = mapAncestorToLocal(flowThread, container, mappedPoint);
   EXPECT_EQ(FloatPoint(10, 120), mappedPoint);
 }
 
+TEST_P(MapCoordinatesTest, MulticolWithBlockAbove) {
+  setBodyInnerHTML(
+      "<div id='container' style='columns:3; column-gap:0; "
+      "column-fill:auto; width:300px; height:200px;'>"
+      "    <div id='target' style='margin-top:-50px; height:100px;'></div>"
+      "</div>");
+
+  LayoutBox* target = toLayoutBox(getLayoutObjectByElementId("target"));
+  LayoutBox* container = toLayoutBox(getLayoutObjectByElementId("container"));
+
+  FloatPoint mappedPoint = mapLocalToAncestor(target, container, FloatPoint());
+  EXPECT_EQ(FloatPoint(0, -50), mappedPoint);
+  mappedPoint = mapAncestorToLocal(target, container, mappedPoint);
+  EXPECT_EQ(FloatPoint(), mappedPoint);
+
+  // Walk each ancestor in the chain separately, to verify each step on the way.
+  LayoutBox* flowThread = target->parentBox();
+  ASSERT_TRUE(flowThread->isLayoutFlowThread());
+
+  mappedPoint = mapLocalToAncestor(target, flowThread, FloatPoint());
+  EXPECT_EQ(FloatPoint(0, -50), mappedPoint);
+  mappedPoint = mapAncestorToLocal(target, flowThread, mappedPoint);
+  EXPECT_EQ(FloatPoint(), mappedPoint);
+
+  mappedPoint = mapLocalToAncestor(flowThread, container, FloatPoint(0, -50));
+  EXPECT_EQ(FloatPoint(0, -50), mappedPoint);
+  mappedPoint = mapAncestorToLocal(flowThread, container, mappedPoint);
+  EXPECT_EQ(FloatPoint(0, -50), mappedPoint);
+}
+
 TEST_P(MapCoordinatesTest, NestedMulticolWithBlock) {
   setBodyInnerHTML(
       "<div id='outerMulticol' style='columns:2; column-gap:0; "
       "column-fill:auto; width:560px; height:215px; border:8px solid; "
       "padding:7px;'>"
       "    <div style='height:10px;'></div>"
       "    <div id='innerMulticol' style='columns:2; column-gap:0; border:8px "
       "solid; padding:7px;'>"
       "        <div style='height:630px;'></div>"
       "        <div id='target' style='width:50px; height:50px;'></div>"
@@ skipping 684 matching lines @@
               LayoutUnit::epsilon());
   EXPECT_NEAR(50.0, matrix.projectPoint(FloatPoint(100.0, 50.0)).y(),
               LayoutUnit::epsilon());
   EXPECT_NEAR(25.0, matrix.projectPoint(FloatPoint(50.0, 100.0)).x(),
               LayoutUnit::epsilon());
   EXPECT_NEAR(100.0, matrix.projectPoint(FloatPoint(50.0, 100.0)).y(),
               LayoutUnit::epsilon());
 }
 
 }  // namespace blink