[New multicol] Avoid 1px tall multicol if percent height is unresolvable.

Source/core/rendering/RenderMultiColumnSet.cpp

 /*
  * Copyright (C) 2012 Apple Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 22 matching lines @@
 
 using namespace std;
 
 namespace WebCore {
 
 RenderMultiColumnSet::RenderMultiColumnSet(RenderFlowThread* flowThread)
     : RenderRegionSet(0, flowThread)
     , m_computedColumnCount(1)
     , m_computedColumnWidth(0)
     , m_computedColumnHeight(0)
-    , m_maxColumnHeight(LayoutUnit::max())
-    , m_minSpaceShortage(LayoutUnit::max())
+    , m_maxColumnHeight(RenderFlowThread::maxLogicalHeight())
+    , m_minSpaceShortage(RenderFlowThread::maxLogicalHeight())
     , m_minimumColumnHeight(0)
 {
 }
 
 RenderMultiColumnSet* RenderMultiColumnSet::createAnonymous(RenderFlowThread* flowThread)
 {
     Document& document = flowThread->document();
     RenderMultiColumnSet* renderer = new RenderMultiColumnSet(flowThread);
     renderer->setDocumentForAnonymous(&document);
     return renderer;
@@ skipping 86 matching lines @@
     if (forcedBreaksCount() > 1 && forcedBreaksCount() >= computedColumnCount()) {
         // Too many forced breaks to allow any implicit breaks. Initial balancing should already
         // have set a good height. There's nothing more we should do.
         return m_computedColumnHeight;
     }
 
     // If the initial guessed column height wasn't enough, stretch it now. Stretch by the lowest
     // amount of space shortage found during layout.
 
     ASSERT(m_minSpaceShortage > 0); // We should never _shrink_ the height!
-    ASSERT(m_minSpaceShortage != LayoutUnit::max()); // If this happens, we probably have a bug.
-    if (m_minSpaceShortage == LayoutUnit::max())
+    ASSERT(m_minSpaceShortage != RenderFlowThread::maxLogicalHeight()); // If this happens, we probably have a bug.
+    if (m_minSpaceShortage == RenderFlowThread::maxLogicalHeight())
         return m_computedColumnHeight; // So bail out rather than looping infinitely.
 
     return m_computedColumnHeight + m_minSpaceShortage;
 }
 
 void RenderMultiColumnSet::clearForcedBreaks()
 {
     m_contentRuns.clear();
 }
 
@@ skipping 21 matching lines @@
 
     // After having calculated an initial column height, the multicol container typically needs at
     // least one more layout pass with a new column height, but if a height was specified, we only
     // need to do this if we think that we need less space than specified. Conversely, if we
     // determined that the columns need to be as tall as the specified height of the container, we
     // have already laid it out correctly, and there's no need for another pass.
 
     if (m_computedColumnHeight == oldColumnHeight)
         return false; // No change. We're done.
 
-    m_minSpaceShortage = LayoutUnit::max();
+    m_minSpaceShortage = RenderFlowThread::maxLogicalHeight();
     clearForcedBreaks();
     return true; // Need another pass.
 }
 
 void RenderMultiColumnSet::recordSpaceShortage(LayoutUnit spaceShortage)
 {
     if (spaceShortage >= m_minSpaceShortage)
         return;
 
     // The space shortage is what we use as our stretch amount. We need a positive number here in
@@ skipping 32 matching lines @@
 
     // Set box logical top.
     ASSERT(!previousSiblingBox() || !previousSiblingBox()->isRenderMultiColumnSet()); // FIXME: multiple set not implemented; need to examine previous set to calculate the correct logical top.
     setLogicalTop(multicolBlock->borderBefore() + multicolBlock->paddingBefore());
 
     // Set box width.
     updateLogicalWidth();
 
     if (multicolBlock->requiresBalancing()) {
         // Set maximum column height. We will not stretch beyond this.
-        m_maxColumnHeight = LayoutUnit::max();
-        if (!multicolStyle->logicalHeight().isAuto())
+        m_maxColumnHeight = RenderFlowThread::maxLogicalHeight();
+        if (!multicolStyle->logicalHeight().isAuto()) {
             m_maxColumnHeight = multicolBlock->computeContentLogicalHeight(multicolStyle->logicalHeight(), -1);
+            if (m_maxColumnHeight == -1)
+                m_maxColumnHeight = RenderFlowThread::maxLogicalHeight();
+        }
         if (!multicolStyle->logicalMaxHeight().isUndefined()) {
             LayoutUnit logicalMaxHeight = multicolBlock->computeContentLogicalHeight(multicolStyle->logicalMaxHeight(), -1);
-            if (m_maxColumnHeight > logicalMaxHeight)
+            if (logicalMaxHeight != -1 && m_maxColumnHeight > logicalMaxHeight)
                 m_maxColumnHeight = logicalMaxHeight;
         }
         m_maxColumnHeight = heightAdjustedForSetOffset(m_maxColumnHeight);
         m_computedColumnHeight = 0; // Restart balancing.
     } else {
         setAndConstrainColumnHeight(heightAdjustedForSetOffset(multicolBlock->columnHeightAvailable()));
     }
 
     clearForcedBreaks();
 
@@ skipping 318 matching lines @@
         fragments.append(fragment);
     }
 }
 
 const char* RenderMultiColumnSet::renderName() const
 {
     return "RenderMultiColumnSet";
 }
 
 }