Rewrite overhanging float arithmetic to work near numeric limits

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

 /*
  * Copyright (C) 2013 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 981 matching lines @@
     LayoutObject* prev = previousSibling();
     while (prev && (!prev->isBox() || !prev->isLayoutBlock() || toLayoutBlock(prev)->avoidsFloats() || toLayoutBlock(prev)->createsNewFormattingContext())) {
         if (prev->isFloating())
             siblingFloatMayIntrude = true;
         prev = prev->previousSibling();
     }
 
     // First add in floats from the parent. Self-collapsing blocks let their parent track any floats that intrude into
     // them (as opposed to floats they contain themselves) so check for those here too. If margin collapsing has moved
     // us up past the top a previous sibling then we need to check for floats from the parent too.
-    LayoutUnit logicalTopOffset = logicalTop();
-    bool parentFloatsMayIntrude = !siblingFloatMayIntrude && (!prev || toLayoutBlockFlow(prev)->isSelfCollapsingBlock() || toLayoutBlock(prev)->logicalTop() > logicalTopOffset)
-        && parentBlockFlow->lowestFloatLogicalBottom() > logicalTopOffset;
+    bool parentFloatsMayIntrude = !siblingFloatMayIntrude && (!prev || toLayoutBlockFlow(prev)->isSelfCollapsingBlock() || toLayoutBlock(prev)->logicalTop() > logicalTop())
+        && parentBlockFlow->lowestFloatLogicalBottom() > logicalTop();
     if (siblingFloatMayIntrude || parentFloatsMayIntrude)
-        addIntrudingFloats(parentBlockFlow, parentBlockFlow->logicalLeftOffsetForContent(), logicalTopOffset);
+        addIntrudingFloats(parentBlockFlow, parentBlockFlow->logicalLeftOffsetForContent(), logicalTop());
 
     // Add overhanging floats from the previous LayoutBlockFlow, but only if it has a float that intrudes into our space.
     if (prev) {
-        LayoutBlockFlow* blockFlow = toLayoutBlockFlow(prev);
-        logicalTopOffset -= blockFlow->logicalTop();
-        if (blockFlow->lowestFloatLogicalBottom() > logicalTopOffset)
-            addIntrudingFloats(blockFlow, LayoutUnit(), logicalTopOffset);
+        LayoutBlockFlow* previousBlockFlow = toLayoutBlockFlow(prev);
+        if (logicalTop() < previousBlockFlow->logicalTop() + previousBlockFlow->lowestFloatLogicalBottom())
+            addIntrudingFloats(previousBlockFlow, LayoutUnit(), logicalTop() - previousBlockFlow->logicalTop());
     }
 
     if (childrenInline()) {
         LayoutUnit changeLogicalTop = LayoutUnit::max();
         LayoutUnit changeLogicalBottom = LayoutUnit::min();
         if (m_floatingObjects) {
             const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
             FloatingObjectSetIterator end = floatingObjectSet.end();
             for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
                 const FloatingObject& floatingObject = *it->get();
@@ skipping 2016 matching lines @@
     // FIXME: Glyph overflow will get lost in this case, but not really a big deal.
     GlyphOverflowAndFallbackFontsMap textBoxDataMap;
     for (ListHashSet<RootInlineBox*>::const_iterator it = lineBoxes.begin(); it != lineBoxes.end(); ++it) {
         RootInlineBox* box = *it;
         box->computeOverflow(box->lineTop(), box->lineBottom(), textBoxDataMap);
     }
     return childrenOverflowChanged;
 }
 
 } // namespace blink