[New Multicolumn] Actual support for layout of column-span:all.

Source/core/rendering/RenderMultiColumnFlowThreadTest.cpp

Index: Source/core/rendering/RenderMultiColumnFlowThreadTest.cpp
diff --git a/Source/core/rendering/RenderMultiColumnFlowThreadTest.cpp b/Source/core/rendering/RenderMultiColumnFlowThreadTest.cpp
index 719607c5ca475f7d9268619f57a29b3fdf2d1841..95581d22faa31dd009bd98a6f2f7517eaa397943 100644
--- a/Source/core/rendering/RenderMultiColumnFlowThreadTest.cpp
+++ b/Source/core/rendering/RenderMultiColumnFlowThreadTest.cpp
@@ -237,6 +237,32 @@ TEST_F(MultiColumnRenderingTest, SubtreeWithSpannerBeforeSpanner)
     EXPECT_EQ(flowThread->containingColumnSpannerSet(document().getElementById("outer")->renderer()), nullptr);
 }
 
+TEST_F(MultiColumnRenderingTest, columnSetAtBlockOffset)
+{
+    setMulticolHTML("<div id='mc' style='line-height:100px;'>text<br>text<br>text<br>text<br>text<div id='spanner1'>spanner</div>text<br>text<div id='spanner2'>text<br>text</div>text</div>");
+    RenderMultiColumnFlowThread* multicolFlowThread = findFlowThread("mc");
+    RenderFlowThread* flowThread = multicolFlowThread; // FIXME: columnSetAtBlockOffset() override is private in RenderMultiColumnFlowThread. :(

[Julien - ping for review, 2014/11/17 23:47:11]

Usually private override are to avoid calling a virtual function when there is
no need. Here I would argue to make it public as there is little harm done.

[mstensho (USE GERRIT), 2014/11/18 13:29:26]

Done.

Generally not a big fan of private overrides myself, as you suddenly end up
having to do stupid upcasts just to be able to call the method.

Made the method final while I was at it, which, with a sufficiently clever
compiler will make direct RenderFlowThread::colmnSetAtBlockOffset() calls
non-virtual. :)

+    EXPECT_EQ(columnSetSignature(multicolFlowThread), "cscsc");
+    RenderMultiColumnSet* columnSet = multicolFlowThread->firstMultiColumnSet();
+    EXPECT_EQ(flowThread->columnSetAtBlockOffset(LayoutUnit(-10000)), columnSet); // negative overflow
+    EXPECT_EQ(flowThread->columnSetAtBlockOffset(LayoutUnit()), columnSet);
+    EXPECT_EQ(flowThread->columnSetAtBlockOffset(LayoutUnit(499)), columnSet); // bottom of last line in first row.
+    EXPECT_EQ(flowThread->columnSetAtBlockOffset(LayoutUnit(599)), columnSet); // empty content in last column in first row
+    columnSet = columnSet->nextSiblingMultiColumnSet(); // first spanner

[Julien - ping for review, 2014/11/17 23:47:12]

How about we have different variable with an explicit name? This would remove
the need for these comments.

[mstensho (USE GERRIT), 2014/11/18 13:29:26]

Done.

+    EXPECT_EQ(flowThread->columnSetAtBlockOffset(LayoutUnit(600)), columnSet);
+    EXPECT_EQ(flowThread->columnSetAtBlockOffset(LayoutUnit(699)), columnSet);
+    columnSet = columnSet->nextSiblingMultiColumnSet(); // second row
+    EXPECT_EQ(flowThread->columnSetAtBlockOffset(LayoutUnit(700)), columnSet);
+    EXPECT_EQ(flowThread->columnSetAtBlockOffset(LayoutUnit(899)), columnSet);
+    columnSet = columnSet->nextSiblingMultiColumnSet(); // second spanner
+    EXPECT_EQ(flowThread->columnSetAtBlockOffset(LayoutUnit(900)), columnSet);
+    EXPECT_EQ(flowThread->columnSetAtBlockOffset(LayoutUnit(1099)), columnSet);
+    columnSet = columnSet->nextSiblingMultiColumnSet(); // third row
+    EXPECT_EQ(flowThread->columnSetAtBlockOffset(LayoutUnit(1100)), columnSet);
+    EXPECT_EQ(flowThread->columnSetAtBlockOffset(LayoutUnit(1199)), columnSet); // bottom of last row
+    EXPECT_EQ(flowThread->columnSetAtBlockOffset(LayoutUnit(10000)), columnSet); // overflow
+}
+
 } // anonymous namespace
 
 } // namespace blink