src/third_party/WebKit/Source/core/rendering/RenderBlockFlow.cpp

   1 /*
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  12  * in the documentation and/or other materials provided with the
  13  * distribution.
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  21  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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  30
  31 #include "config.h"
  32 #include "core/rendering/RenderBlockFlow.h"
  33
  34 #include "core/accessibility/AXObjectCache.h"
  35 #include "core/frame/FrameView.h"
  36 #include "core/rendering/FastTextAutosizer.h"
  37 #include "core/rendering/HitTestLocation.h"
  38 #include "core/rendering/LayoutRepainter.h"
  39 #include "core/rendering/RenderFlowThread.h"
  40 #include "core/rendering/RenderLayer.h"
  41 #include "core/rendering/RenderMultiColumnFlowThread.h"
  42 #include "core/rendering/RenderText.h"
  43 #include "core/rendering/RenderView.h"
  44 #include "core/rendering/line/LineWidth.h"
  45 #include "core/rendering/svg/SVGTextRunRenderingContext.h"
  46 #include "platform/text/BidiTextRun.h"
  47
  48 using namespace std;
  49
  50 namespace WebCore {
  51
  52 bool RenderBlockFlow::s_canPropagateFloatIntoSibling = false;
  53
  54 struct SameSizeAsMarginInfo {
  55     uint16_t bitfields;
  56     LayoutUnit margins[2];
  57 };
  58
  59 COMPILE_ASSERT(sizeof(RenderBlockFlow::MarginValues) == sizeof(LayoutUnit[4]), MarginValues_should_stay_small);
  60
  61 class MarginInfo {
  62     // Collapsing flags for whether we can collapse our margins with our children's margins.
  63     bool m_canCollapseWithChildren : 1;
  64     bool m_canCollapseMarginBeforeWithChildren : 1;
  65     bool m_canCollapseMarginAfterWithChildren : 1;
  66     bool m_canCollapseMarginAfterWithLastChild: 1;
  67
  68     // Whether or not we are a quirky container, i.e., do we collapse away top and bottom
  69     // margins in our container. Table cells and the body are the common examples. We
  70     // also have a custom style property for Safari RSS to deal with TypePad blog articles.
  71     bool m_quirkContainer : 1;
  72
  73     // This flag tracks whether we are still looking at child margins that can all collapse together at the beginning of a block.
  74     // They may or may not collapse with the top margin of the block (|m_canCollapseTopWithChildren| tells us that), but they will
  75     // always be collapsing with one another. This variable can remain set to true through multiple iterations
  76     // as long as we keep encountering self-collapsing blocks.
  77     bool m_atBeforeSideOfBlock : 1;
  78
  79     // This flag is set when we know we're examining bottom margins and we know we're at the bottom of the block.
  80     bool m_atAfterSideOfBlock : 1;
  81
  82     // These variables are used to detect quirky margins that we need to collapse away (in table cells
  83     // and in the body element).
  84     bool m_hasMarginBeforeQuirk : 1;
  85     bool m_hasMarginAfterQuirk : 1;
  86     bool m_determinedMarginBeforeQuirk : 1;
  87
  88     bool m_discardMargin : 1;
  89
  90     // These flags track the previous maximal positive and negative margins.
  91     LayoutUnit m_positiveMargin;
  92     LayoutUnit m_negativeMargin;
  93
  94 public:
  95     MarginInfo(RenderBlockFlow*, LayoutUnit beforeBorderPadding, LayoutUnit afterBorderPadding);
  96
  97     void setAtBeforeSideOfBlock(bool b) { m_atBeforeSideOfBlock = b; }
  98     void setAtAfterSideOfBlock(bool b) { m_atAfterSideOfBlock = b; }
  99     void clearMargin()
 100     {
 101         m_positiveMargin = 0;
 102         m_negativeMargin = 0;
 103     }
 104     void setHasMarginBeforeQuirk(bool b) { m_hasMarginBeforeQuirk = b; }
 105     void setHasMarginAfterQuirk(bool b) { m_hasMarginAfterQuirk = b; }
 106     void setDeterminedMarginBeforeQuirk(bool b) { m_determinedMarginBeforeQuirk = b; }
 107     void setPositiveMargin(LayoutUnit p) { ASSERT(!m_discardMargin); m_positiveMargin = p; }
 108     void setNegativeMargin(LayoutUnit n) { ASSERT(!m_discardMargin); m_negativeMargin = n; }
 109     void setPositiveMarginIfLarger(LayoutUnit p)
 110     {
 111         ASSERT(!m_discardMargin);
 112         if (p > m_positiveMargin)
 113             m_positiveMargin = p;
 114     }
 115     void setNegativeMarginIfLarger(LayoutUnit n)
 116     {
 117         ASSERT(!m_discardMargin);
 118         if (n > m_negativeMargin)
 119             m_negativeMargin = n;
 120     }
 121
 122     void setMargin(LayoutUnit p, LayoutUnit n) { ASSERT(!m_discardMargin); m_positiveMargin = p; m_negativeMargin = n; }
 123     void setCanCollapseMarginAfterWithChildren(bool collapse) { m_canCollapseMarginAfterWithChildren = collapse; }
 124     void setCanCollapseMarginAfterWithLastChild(bool collapse) { m_canCollapseMarginAfterWithLastChild = collapse; }
 125     void setDiscardMargin(bool value) { m_discardMargin = value; }
 126
 127     bool atBeforeSideOfBlock() const { return m_atBeforeSideOfBlock; }
 128     bool canCollapseWithMarginBefore() const { return m_atBeforeSideOfBlock && m_canCollapseMarginBeforeWithChildren; }
 129     bool canCollapseWithMarginAfter() const { return m_atAfterSideOfBlock && m_canCollapseMarginAfterWithChildren; }
 130     bool canCollapseMarginBeforeWithChildren() const { return m_canCollapseMarginBeforeWithChildren; }
 131     bool canCollapseMarginAfterWithChildren() const { return m_canCollapseMarginAfterWithChildren; }
 132     bool canCollapseMarginAfterWithLastChild() const { return m_canCollapseMarginAfterWithLastChild; }
 133     bool quirkContainer() const { return m_quirkContainer; }
 134     bool determinedMarginBeforeQuirk() const { return m_determinedMarginBeforeQuirk; }
 135     bool hasMarginBeforeQuirk() const { return m_hasMarginBeforeQuirk; }
 136     bool hasMarginAfterQuirk() const { return m_hasMarginAfterQuirk; }
 137     LayoutUnit positiveMargin() const { return m_positiveMargin; }
 138     LayoutUnit negativeMargin() const { return m_negativeMargin; }
 139     bool discardMargin() const { return m_discardMargin; }
 140     LayoutUnit margin() const { return m_positiveMargin - m_negativeMargin; }
 141 };
 142 static bool inNormalFlow(RenderBox* child)
 143 {
 144     RenderBlock* curr = child->containingBlock();
 145     RenderView* renderView = child->view();
 146     while (curr && curr != renderView) {
 147         if (curr->hasColumns() || curr->isRenderFlowThread())
 148             return true;
 149         if (curr->isFloatingOrOutOfFlowPositioned())
 150             return false;
 151         curr = curr->containingBlock();
 152     }
 153     return true;
 154 }
 155
 156 RenderBlockFlow::RenderBlockFlow(ContainerNode* node)
 157     : RenderBlock(node)
 158 {
 159     COMPILE_ASSERT(sizeof(MarginInfo) == sizeof(SameSizeAsMarginInfo), MarginInfo_should_stay_small);
 160 }
 161
 162 RenderBlockFlow::~RenderBlockFlow()
 163 {
 164 }
 165
 166 RenderBlockFlow* RenderBlockFlow::createAnonymous(Document* document)
 167 {
 168     RenderBlockFlow* renderer = new RenderBlockFlow(0);
 169     renderer->setDocumentForAnonymous(document);
 170     return renderer;
 171 }
 172
 173 RenderObject* RenderBlockFlow::layoutSpecialExcludedChild(bool relayoutChildren, SubtreeLayoutScope& layoutScope)
 174 {
 175     RenderMultiColumnFlowThread* flowThread = multiColumnFlowThread();
 176     if (!flowThread)
 177         return 0;
 178     setLogicalTopForChild(flowThread, borderBefore() + paddingBefore());
 179     flowThread->layoutColumns(relayoutChildren, layoutScope);
 180     determineLogicalLeftPositionForChild(flowThread);
 181     return flowThread;
 182 }
 183
 184 bool RenderBlockFlow::updateLogicalWidthAndColumnWidth()
 185 {
 186     bool relayoutChildren = RenderBlock::updateLogicalWidthAndColumnWidth();
 187     if (RenderMultiColumnFlowThread* flowThread = multiColumnFlowThread()) {
 188         if (flowThread->needsNewWidth())
 189             return true;
 190     }
 191     return relayoutChildren;
 192 }
 193
 194 void RenderBlockFlow::checkForPaginationLogicalHeightChange(LayoutUnit& pageLogicalHeight, bool& pageLogicalHeightChanged, bool& hasSpecifiedPageLogicalHeight)
 195 {
 196     if (RenderMultiColumnFlowThread* flowThread = multiColumnFlowThread()) {
 197         LogicalExtentComputedValues computedValues;
 198         computeLogicalHeight(LayoutUnit(), logicalTop(), computedValues);
 199         LayoutUnit columnHeight = computedValues.m_extent - borderAndPaddingLogicalHeight() - scrollbarLogicalHeight();
 200         pageLogicalHeightChanged = columnHeight != flowThread->columnHeightAvailable();
 201         flowThread->setColumnHeightAvailable(std::max<LayoutUnit>(columnHeight, 0));
 202     } else if (hasColumns()) {
 203         ColumnInfo* colInfo = columnInfo();
 204
 205         if (!pageLogicalHeight) {
 206             LayoutUnit oldLogicalHeight = logicalHeight();
 207             setLogicalHeight(0);
 208             // We need to go ahead and set our explicit page height if one exists, so that we can
 209             // avoid doing two layout passes.
 210             updateLogicalHeight();
 211             LayoutUnit columnHeight = contentLogicalHeight();
 212             if (columnHeight > 0) {
 213                 pageLogicalHeight = columnHeight;
 214                 hasSpecifiedPageLogicalHeight = true;
 215             }
 216             setLogicalHeight(oldLogicalHeight);
 217         }
 218         if (colInfo->columnHeight() != pageLogicalHeight && everHadLayout()) {
 219             colInfo->setColumnHeight(pageLogicalHeight);
 220             pageLogicalHeightChanged = true;
 221         }
 222
 223         if (!hasSpecifiedPageLogicalHeight && !pageLogicalHeight)
 224             colInfo->clearForcedBreaks();
 225     } else if (isRenderFlowThread()) {
 226         RenderFlowThread* flowThread = toRenderFlowThread(this);
 227
 228         // FIXME: This is a hack to always make sure we have a page logical height, if said height
 229         // is known. The page logical height thing in LayoutState is meaningless for flow
 230         // thread-based pagination (page height isn't necessarily uniform throughout the flow
 231         // thread), but as long as it is used universally as a means to determine whether page
 232         // height is known or not, we need this. Page height is unknown when column balancing is
 233         // enabled and flow thread height is still unknown (i.e. during the first layout pass). When
 234         // it's unknown, we need to prevent the pagination code from assuming page breaks everywhere
 235         // and thereby eating every top margin. It should be trivial to clean up and get rid of this
 236         // hack once the old multicol implementation is gone.
 237         pageLogicalHeight = flowThread->isPageLogicalHeightKnown() ? LayoutUnit(1) : LayoutUnit(0);
 238
 239         pageLogicalHeightChanged = flowThread->pageLogicalSizeChanged();
 240     }
 241 }
 242
 243 bool RenderBlockFlow::shouldRelayoutForPagination(LayoutUnit& pageLogicalHeight, LayoutUnit layoutOverflowLogicalBottom) const
 244 {
 245     // FIXME: We don't balance properly at all in the presence of forced page breaks. We need to understand what
 246     // the distance between forced page breaks is so that we can avoid making the minimum column height too tall.
 247     ColumnInfo* colInfo = columnInfo();
 248     LayoutUnit columnHeight = pageLogicalHeight;
 249     const int minColumnCount = colInfo->forcedBreaks() + 1;
 250     const int desiredColumnCount = colInfo->desiredColumnCount();
 251     if (minColumnCount >= desiredColumnCount) {
 252         // The forced page breaks are in control of the balancing. Just set the column height to the
 253         // maximum page break distance.
 254         if (!pageLogicalHeight) {
 255             LayoutUnit distanceBetweenBreaks = max<LayoutUnit>(colInfo->maximumDistanceBetweenForcedBreaks(),
 256                 view()->layoutState()->pageLogicalOffset(*this, borderBefore() + paddingBefore() + layoutOverflowLogicalBottom) - colInfo->forcedBreakOffset());
 257             columnHeight = max(colInfo->minimumColumnHeight(), distanceBetweenBreaks);
 258         }
 259     } else if (layoutOverflowLogicalBottom > boundedMultiply(pageLogicalHeight, desiredColumnCount)) {
 260         // Now that we know the intrinsic height of the columns, we have to rebalance them.
 261         columnHeight = max<LayoutUnit>(colInfo->minimumColumnHeight(), ceilf(layoutOverflowLogicalBottom.toFloat() / desiredColumnCount));
 262     }
 263
 264     if (columnHeight && columnHeight != pageLogicalHeight) {
 265         pageLogicalHeight = columnHeight;
 266         return true;
 267     }
 268
 269     return false;
 270 }
 271
 272 void RenderBlockFlow::setColumnCountAndHeight(unsigned count, LayoutUnit pageLogicalHeight)
 273 {
 274     ColumnInfo* colInfo = columnInfo();
 275     if (pageLogicalHeight)
 276         colInfo->setColumnCountAndHeight(count, pageLogicalHeight);
 277
 278     if (columnCount(colInfo)) {
 279         setLogicalHeight(borderBefore() + paddingBefore() + colInfo->columnHeight() + borderAfter() + paddingAfter() + scrollbarLogicalHeight());
 280         m_overflow.clear();
 281     }
 282 }
 283
 284 bool RenderBlockFlow::isSelfCollapsingBlock() const
 285 {
 286     m_hasOnlySelfCollapsingChildren = RenderBlock::isSelfCollapsingBlock();
 287     return m_hasOnlySelfCollapsingChildren;
 288 }
 289
 290 void RenderBlockFlow::layoutBlock(bool relayoutChildren)
 291 {
 292     ASSERT(needsLayout());
 293     ASSERT(isInlineBlockOrInlineTable() || !isInline());
 294
 295     // If we are self-collapsing with self-collapsing descendants this will get set to save us burrowing through our
 296     // descendants every time in |isSelfCollapsingBlock|. We reset it here so that |isSelfCollapsingBlock| attempts to burrow
 297     // at least once and so that it always gives a reliable result reflecting the latest layout.
 298     m_hasOnlySelfCollapsingChildren = false;
 299
 300     if (!relayoutChildren && simplifiedLayout())
 301         return;
 302
 303     SubtreeLayoutScope layoutScope(*this);
 304
 305     // Multiple passes might be required for column and pagination based layout
 306     // In the case of the old column code the number of passes will only be two
 307     // however, in the newer column code the number of passes could equal the
 308     // number of columns.
 309     bool done = false;
 310     LayoutUnit pageLogicalHeight = 0;
 311     LayoutRepainter repainter(*this, checkForPaintInvalidationDuringLayout());
 312     while (!done)
 313         done = layoutBlockFlow(relayoutChildren, pageLogicalHeight, layoutScope);
 314
 315     fitBorderToLinesIfNeeded();
 316
 317     RenderView* renderView = view();
 318     if (renderView->layoutState()->pageLogicalHeight())
 319         setPageLogicalOffset(renderView->layoutState()->pageLogicalOffset(*this, logicalTop()));
 320
 321     updateLayerTransformAfterLayout();
 322
 323     // Update our scroll information if we're overflow:auto/scroll/hidden now that we know if
 324     // we overflow or not.
 325     updateScrollInfoAfterLayout();
 326
 327     // Repaint with our new bounds if they are different from our old bounds.
 328     bool didFullRepaint = repainter.repaintAfterLayout();
 329     if (!didFullRepaint && m_repaintLogicalTop != m_repaintLogicalBottom && (style()->visibility() == VISIBLE || enclosingLayer()->hasVisibleContent())) {
 330         if (RuntimeEnabledFeatures::repaintAfterLayoutEnabled())
 331             setShouldInvalidateOverflowForPaint(true);
 332         else
 333             invalidatePaintForOverflow();
 334     }
 335     clearNeedsLayout();
 336 }
 337
 338 inline bool RenderBlockFlow::layoutBlockFlow(bool relayoutChildren, LayoutUnit &pageLogicalHeight, SubtreeLayoutScope& layoutScope)
 339 {
 340     LayoutUnit oldLeft = logicalLeft();
 341     if (updateLogicalWidthAndColumnWidth())
 342         relayoutChildren = true;
 343
 344     rebuildFloatsFromIntruding();
 345
 346     bool pageLogicalHeightChanged = false;
 347     bool hasSpecifiedPageLogicalHeight = false;
 348     checkForPaginationLogicalHeightChange(pageLogicalHeight, pageLogicalHeightChanged, hasSpecifiedPageLogicalHeight);
 349     if (pageLogicalHeightChanged)
 350         relayoutChildren = true;
 351
 352     LayoutState state(*this, locationOffset(), pageLogicalHeight, pageLogicalHeightChanged, columnInfo());
 353
 354     // We use four values, maxTopPos, maxTopNeg, maxBottomPos, and maxBottomNeg, to track
 355     // our current maximal positive and negative margins. These values are used when we
 356     // are collapsed with adjacent blocks, so for example, if you have block A and B
 357     // collapsing together, then you'd take the maximal positive margin from both A and B
 358     // and subtract it from the maximal negative margin from both A and B to get the
 359     // true collapsed margin. This algorithm is recursive, so when we finish layout()
 360     // our block knows its current maximal positive/negative values.
 361     //
 362     // Start out by setting our margin values to our current margins. Table cells have
 363     // no margins, so we don't fill in the values for table cells.
 364     if (!isTableCell()) {
 365         initMaxMarginValues();
 366         setHasMarginBeforeQuirk(style()->hasMarginBeforeQuirk());
 367         setHasMarginAfterQuirk(style()->hasMarginAfterQuirk());
 368         setPaginationStrut(0);
 369     }
 370
 371     LayoutUnit beforeEdge = borderBefore() + paddingBefore();
 372     LayoutUnit afterEdge = borderAfter() + paddingAfter() + scrollbarLogicalHeight();
 373     LayoutUnit previousHeight = logicalHeight();
 374     setLogicalHeight(beforeEdge);
 375
 376     m_repaintLogicalTop = 0;
 377     m_repaintLogicalBottom = 0;
 378     if (!firstChild() && !isAnonymousBlock())
 379         setChildrenInline(true);
 380
 381     FastTextAutosizer::LayoutScope fastTextAutosizerLayoutScope(this);
 382
 383     if (childrenInline())
 384         layoutInlineChildren(relayoutChildren, m_repaintLogicalTop, m_repaintLogicalBottom, afterEdge);
 385     else
 386         layoutBlockChildren(relayoutChildren, layoutScope, beforeEdge, afterEdge);
 387
 388     // Expand our intrinsic height to encompass floats.
 389     if (lowestFloatLogicalBottom() > (logicalHeight() - afterEdge) && createsBlockFormattingContext())
 390         setLogicalHeight(lowestFloatLogicalBottom() + afterEdge);
 391
 392     if (RenderMultiColumnFlowThread* flowThread = multiColumnFlowThread()) {
 393         if (flowThread->recalculateColumnHeights()) {
 394             setChildNeedsLayout(MarkOnlyThis);
 395             return false;
 396         }
 397     } else if (hasColumns()) {
 398         OwnPtr<RenderOverflow> savedOverflow = m_overflow.release();
 399         if (childrenInline())
 400             addOverflowFromInlineChildren();
 401         else
 402             addOverflowFromBlockChildren();
 403         LayoutUnit layoutOverflowLogicalBottom = (isHorizontalWritingMode() ? layoutOverflowRect().maxY() : layoutOverflowRect().maxX()) - borderBefore() - paddingBefore();
 404         m_overflow = savedOverflow.release();
 405
 406         if (!hasSpecifiedPageLogicalHeight && shouldRelayoutForPagination(pageLogicalHeight, layoutOverflowLogicalBottom)) {
 407             setEverHadLayout(true);
 408             return false;
 409         }
 410
 411         setColumnCountAndHeight(ceilf(layoutOverflowLogicalBottom.toFloat() / pageLogicalHeight.toFloat()), pageLogicalHeight.toFloat());
 412     }
 413
 414     if (shouldBreakAtLineToAvoidWidow()) {
 415         setEverHadLayout(true);
 416         return false;
 417     }
 418
 419     // Calculate our new height.
 420     LayoutUnit oldHeight = logicalHeight();
 421     LayoutUnit oldClientAfterEdge = clientLogicalBottom();
 422
 423     updateLogicalHeight();
 424     LayoutUnit newHeight = logicalHeight();
 425     if (oldHeight > newHeight && !childrenInline()) {
 426         // One of our children's floats may have become an overhanging float for us.
 427         for (RenderObject* child = lastChild(); child; child = child->previousSibling()) {
 428             if (child->isRenderBlockFlow() && !child->isFloatingOrOutOfFlowPositioned()) {
 429                 RenderBlockFlow* block = toRenderBlockFlow(child);
 430                 if (block->lowestFloatLogicalBottom() + block->logicalTop() <= newHeight)
 431                     break;
 432                 addOverhangingFloats(block, false);
 433             }
 434         }
 435     }
 436
 437     bool heightChanged = (previousHeight != newHeight);
 438     if (heightChanged)
 439         relayoutChildren = true;
 440
 441     layoutPositionedObjects(relayoutChildren || isDocumentElement(), oldLeft != logicalLeft() ? ForcedLayoutAfterContainingBlockMoved : DefaultLayout);
 442
 443     computeRegionRangeForBlock(flowThreadContainingBlock());
 444
 445     // Add overflow from children (unless we're multi-column, since in that case all our child overflow is clipped anyway).
 446     computeOverflow(oldClientAfterEdge);
 447
 448     return true;
 449 }
 450
 451 void RenderBlockFlow::determineLogicalLeftPositionForChild(RenderBox* child, ApplyLayoutDeltaMode applyDelta)
 452 {
 453     LayoutUnit startPosition = borderStart() + paddingStart();
 454     if (style()->shouldPlaceBlockDirectionScrollbarOnLogicalLeft())
 455         startPosition -= verticalScrollbarWidth();
 456     LayoutUnit totalAvailableLogicalWidth = borderAndPaddingLogicalWidth() + availableLogicalWidth();
 457
 458     // Add in our start margin.
 459     LayoutUnit childMarginStart = marginStartForChild(child);
 460     LayoutUnit newPosition = startPosition + childMarginStart;
 461
 462     // Some objects (e.g., tables, horizontal rules, overflow:auto blocks) avoid floats. They need
 463     // to shift over as necessary to dodge any floats that might get in the way.
 464     if (child->avoidsFloats() && containsFloats() && !flowThreadContainingBlock())
 465         newPosition += computeStartPositionDeltaForChildAvoidingFloats(child, marginStartForChild(child));
 466
 467     setLogicalLeftForChild(child, style()->isLeftToRightDirection() ? newPosition : totalAvailableLogicalWidth - newPosition - logicalWidthForChild(child), applyDelta);
 468 }
 469
 470 void RenderBlockFlow::setLogicalLeftForChild(RenderBox* child, LayoutUnit logicalLeft, ApplyLayoutDeltaMode applyDelta)
 471 {
 472     if (isHorizontalWritingMode()) {
 473         if (applyDelta == ApplyLayoutDelta && !RuntimeEnabledFeatures::repaintAfterLayoutEnabled())
 474             view()->addLayoutDelta(LayoutSize(child->x() - logicalLeft, 0));
 475         child->setX(logicalLeft);
 476     } else {
 477         if (applyDelta == ApplyLayoutDelta && !RuntimeEnabledFeatures::repaintAfterLayoutEnabled())
 478             view()->addLayoutDelta(LayoutSize(0, child->y() - logicalLeft));
 479         child->setY(logicalLeft);
 480     }
 481 }
 482
 483 void RenderBlockFlow::setLogicalTopForChild(RenderBox* child, LayoutUnit logicalTop, ApplyLayoutDeltaMode applyDelta)
 484 {
 485     if (isHorizontalWritingMode()) {
 486         if (applyDelta == ApplyLayoutDelta && !RuntimeEnabledFeatures::repaintAfterLayoutEnabled())
 487             view()->addLayoutDelta(LayoutSize(0, child->y() - logicalTop));
 488         child->setY(logicalTop);
 489     } else {
 490         if (applyDelta == ApplyLayoutDelta && !RuntimeEnabledFeatures::repaintAfterLayoutEnabled())
 491             view()->addLayoutDelta(LayoutSize(child->x() - logicalTop, 0));
 492         child->setX(logicalTop);
 493     }
 494 }
 495
 496 void RenderBlockFlow::layoutBlockChild(RenderBox* child, MarginInfo& marginInfo, LayoutUnit& previousFloatLogicalBottom)
 497 {
 498     LayoutUnit oldPosMarginBefore = maxPositiveMarginBefore();
 499     LayoutUnit oldNegMarginBefore = maxNegativeMarginBefore();
 500
 501     // The child is a normal flow object. Compute the margins we will use for collapsing now.
 502     child->computeAndSetBlockDirectionMargins(this);
 503
 504     // Try to guess our correct logical top position. In most cases this guess will
 505     // be correct. Only if we're wrong (when we compute the real logical top position)
 506     // will we have to potentially relayout.
 507     LayoutUnit estimateWithoutPagination;
 508     LayoutUnit logicalTopEstimate = estimateLogicalTopPosition(child, marginInfo, estimateWithoutPagination);
 509
 510     // Cache our old rect so that we can dirty the proper repaint rects if the child moves.
 511     LayoutRect oldRect = child->frameRect();
 512     LayoutUnit oldLogicalTop = logicalTopForChild(child);
 513
 514 #if ASSERT_ENABLED
 515     LayoutSize oldLayoutDelta = RuntimeEnabledFeatures::repaintAfterLayoutEnabled() ? LayoutSize() : view()->layoutDelta();
 516 #endif
 517     // Go ahead and position the child as though it didn't collapse with the top.
 518     setLogicalTopForChild(child, logicalTopEstimate, ApplyLayoutDelta);
 519
 520     RenderBlock* childRenderBlock = child->isRenderBlock() ? toRenderBlock(child) : 0;
 521     RenderBlockFlow* childRenderBlockFlow = (childRenderBlock && child->isRenderBlockFlow()) ? toRenderBlockFlow(child) : 0;
 522     bool markDescendantsWithFloats = false;
 523     if (logicalTopEstimate != oldLogicalTop && !child->avoidsFloats() && childRenderBlock && childRenderBlock->containsFloats()) {
 524         markDescendantsWithFloats = true;
 525     } else if (UNLIKELY(logicalTopEstimate.mightBeSaturated())) {
 526         // logicalTopEstimate, returned by estimateLogicalTopPosition, might be saturated for
 527         // very large elements. If it does the comparison with oldLogicalTop might yield a
 528         // false negative as adding and removing margins, borders etc from a saturated number
 529         // might yield incorrect results. If this is the case always mark for layout.
 530         markDescendantsWithFloats = true;
 531     } else if (!child->avoidsFloats() || child->shrinkToAvoidFloats()) {
 532         // If an element might be affected by the presence of floats, then always mark it for
 533         // layout.
 534         LayoutUnit fb = max(previousFloatLogicalBottom, lowestFloatLogicalBottom());
 535         if (fb > logicalTopEstimate)
 536             markDescendantsWithFloats = true;
 537     }
 538
 539     if (childRenderBlockFlow) {
 540         if (markDescendantsWithFloats)
 541             childRenderBlockFlow->markAllDescendantsWithFloatsForLayout();
 542         if (!child->isWritingModeRoot())
 543             previousFloatLogicalBottom = max(previousFloatLogicalBottom, oldLogicalTop + childRenderBlockFlow->lowestFloatLogicalBottom());
 544     }
 545
 546     SubtreeLayoutScope layoutScope(*child);
 547     if (!child->needsLayout())
 548         child->markForPaginationRelayoutIfNeeded(layoutScope);
 549
 550     bool childHadLayout = child->everHadLayout();
 551     bool childNeededLayout = child->needsLayout();
 552     if (childNeededLayout)
 553         child->layout();
 554
 555     // Cache if we are at the top of the block right now.
 556     bool atBeforeSideOfBlock = marginInfo.atBeforeSideOfBlock();
 557     bool childIsSelfCollapsing = child->isSelfCollapsingBlock();
 558
 559     // Now determine the correct ypos based off examination of collapsing margin
 560     // values.
 561     LayoutUnit logicalTopBeforeClear = collapseMargins(child, marginInfo, childIsSelfCollapsing);
 562
 563     // Now check for clear.
 564     LayoutUnit logicalTopAfterClear = clearFloatsIfNeeded(child, marginInfo, oldPosMarginBefore, oldNegMarginBefore, logicalTopBeforeClear, childIsSelfCollapsing);
 565
 566     bool paginated = view()->layoutState()->isPaginated();
 567     if (paginated) {
 568         logicalTopAfterClear = adjustBlockChildForPagination(logicalTopAfterClear, estimateWithoutPagination, child,
 569             atBeforeSideOfBlock && logicalTopBeforeClear == logicalTopAfterClear);
 570     }
 571
 572     setLogicalTopForChild(child, logicalTopAfterClear, ApplyLayoutDelta);
 573
 574     // Now we have a final top position. See if it really does end up being different from our estimate.
 575     // clearFloatsIfNeeded can also mark the child as needing a layout even though we didn't move. This happens
 576     // when collapseMargins dynamically adds overhanging floats because of a child with negative margins.
 577     if (logicalTopAfterClear != logicalTopEstimate || child->needsLayout() || (paginated && childRenderBlock && childRenderBlock->shouldBreakAtLineToAvoidWidow())) {
 578         SubtreeLayoutScope layoutScope(*child);
 579         if (child->shrinkToAvoidFloats()) {
 580             // The child's width depends on the line width.
 581             // When the child shifts to clear an item, its width can
 582             // change (because it has more available line width).
 583             // So go ahead and mark the item as dirty.
 584             layoutScope.setChildNeedsLayout(child);
 585         }
 586
 587         if (childRenderBlock) {
 588             if (!child->avoidsFloats() && childRenderBlock->containsFloats())
 589                 childRenderBlockFlow->markAllDescendantsWithFloatsForLayout();
 590             if (!child->needsLayout())
 591                 child->markForPaginationRelayoutIfNeeded(layoutScope);
 592         }
 593
 594         // Our guess was wrong. Make the child lay itself out again.
 595         child->layoutIfNeeded();
 596     }
 597
 598     // If we previously encountered a self-collapsing sibling of this child that had clearance then
 599     // we set this bit to ensure we would not collapse the child's margins, and those of any subsequent
 600     // self-collapsing siblings, with our parent. If this child is not self-collapsing then it can
 601     // collapse its margins with the parent so reset the bit.
 602     if (!marginInfo.canCollapseMarginAfterWithLastChild() && !childIsSelfCollapsing)
 603         marginInfo.setCanCollapseMarginAfterWithLastChild(true);
 604
 605     // We are no longer at the top of the block if we encounter a non-empty child.
 606     // This has to be done after checking for clear, so that margins can be reset if a clear occurred.
 607     if (marginInfo.atBeforeSideOfBlock() && !childIsSelfCollapsing)
 608         marginInfo.setAtBeforeSideOfBlock(false);
 609
 610     // Now place the child in the correct left position
 611     determineLogicalLeftPositionForChild(child, ApplyLayoutDelta);
 612
 613     LayoutSize childOffset = child->location() - oldRect.location();
 614
 615     // Update our height now that the child has been placed in the correct position.
 616     setLogicalHeight(logicalHeight() + logicalHeightForChild(child));
 617     if (mustSeparateMarginAfterForChild(child)) {
 618         setLogicalHeight(logicalHeight() + marginAfterForChild(child));
 619         marginInfo.clearMargin();
 620     }
 621     // If the child has overhanging floats that intrude into following siblings (or possibly out
 622     // of this block), then the parent gets notified of the floats now.
 623     if (childRenderBlockFlow)
 624         addOverhangingFloats(childRenderBlockFlow, !childNeededLayout);
 625
 626     if (childOffset.width() || childOffset.height()) {
 627         if (!RuntimeEnabledFeatures::repaintAfterLayoutEnabled())
 628             view()->addLayoutDelta(childOffset);
 629
 630         // If the child moved, we have to repaint it as well as any floating/positioned
 631         // descendants. An exception is if we need a layout. In this case, we know we're going to
 632         // repaint ourselves (and the child) anyway.
 633         if (RuntimeEnabledFeatures::repaintAfterLayoutEnabled() && childHadLayout && !selfNeedsLayout())
 634             child->repaintOverhangingFloats(true);
 635         else if (childHadLayout && !selfNeedsLayout() && child->checkForPaintInvalidationDuringLayout())
 636             child->repaintDuringLayoutIfMoved(oldRect);
 637     }
 638
 639     if (!childHadLayout && child->checkForPaintInvalidation()) {
 640         if (!RuntimeEnabledFeatures::repaintAfterLayoutEnabled())
 641             child->paintInvalidationForWholeRenderer();
 642         child->repaintOverhangingFloats(true);
 643     }
 644
 645     if (paginated) {
 646         // Check for an after page/column break.
 647         LayoutUnit newHeight = applyAfterBreak(child, logicalHeight(), marginInfo);
 648         if (newHeight != height())
 649             setLogicalHeight(newHeight);
 650     }
 651
 652     if (!RuntimeEnabledFeatures::repaintAfterLayoutEnabled()) {
 653         ASSERT(view()->layoutDeltaMatches(oldLayoutDelta));
 654     }
 655 }
 656
 657 LayoutUnit RenderBlockFlow::adjustBlockChildForPagination(LayoutUnit logicalTopAfterClear, LayoutUnit estimateWithoutPagination, RenderBox* child, bool atBeforeSideOfBlock)
 658 {
 659     RenderBlock* childRenderBlock = child->isRenderBlock() ? toRenderBlock(child) : 0;
 660
 661     if (estimateWithoutPagination != logicalTopAfterClear) {
 662         // Our guess prior to pagination movement was wrong. Before we attempt to paginate, let's try again at the new
 663         // position.
 664         setLogicalHeight(logicalTopAfterClear);
 665         setLogicalTopForChild(child, logicalTopAfterClear, ApplyLayoutDelta);
 666
 667         if (child->shrinkToAvoidFloats()) {
 668             // The child's width depends on the line width.
 669             // When the child shifts to clear an item, its width can
 670             // change (because it has more available line width).
 671             // So go ahead and mark the item as dirty.
 672             child->setChildNeedsLayout(MarkOnlyThis);
 673         }
 674
 675         SubtreeLayoutScope layoutScope(*child);
 676
 677         if (childRenderBlock) {
 678             if (!child->avoidsFloats() && childRenderBlock->containsFloats())
 679                 toRenderBlockFlow(childRenderBlock)->markAllDescendantsWithFloatsForLayout();
 680             if (!child->needsLayout())
 681                 child->markForPaginationRelayoutIfNeeded(layoutScope);
 682         }
 683
 684         // Our guess was wrong. Make the child lay itself out again.
 685         child->layoutIfNeeded();
 686     }
 687
 688     LayoutUnit oldTop = logicalTopAfterClear;
 689
 690     // If the object has a page or column break value of "before", then we should shift to the top of the next page.
 691     LayoutUnit result = applyBeforeBreak(child, logicalTopAfterClear);
 692
 693     // For replaced elements and scrolled elements, we want to shift them to the next page if they don't fit on the current one.
 694     LayoutUnit logicalTopBeforeUnsplittableAdjustment = result;
 695     LayoutUnit logicalTopAfterUnsplittableAdjustment = adjustForUnsplittableChild(child, result);
 696
 697     LayoutUnit paginationStrut = 0;
 698     LayoutUnit unsplittableAdjustmentDelta = logicalTopAfterUnsplittableAdjustment - logicalTopBeforeUnsplittableAdjustment;
 699     LayoutUnit childLogicalHeight = child->logicalHeight();
 700     if (unsplittableAdjustmentDelta) {
 701         setPageBreak(result, childLogicalHeight - unsplittableAdjustmentDelta);
 702         paginationStrut = unsplittableAdjustmentDelta;
 703     } else if (childRenderBlock && childRenderBlock->paginationStrut()) {
 704         paginationStrut = childRenderBlock->paginationStrut();
 705     }
 706
 707     if (paginationStrut) {
 708         // We are willing to propagate out to our parent block as long as we were at the top of the block prior
 709         // to collapsing our margins, and as long as we didn't clear or move as a result of other pagination.
 710         if (atBeforeSideOfBlock && oldTop == result && !isOutOfFlowPositioned() && !isTableCell()) {
 711             // FIXME: Should really check if we're exceeding the page height before propagating the strut, but we don't
 712             // have all the information to do so (the strut only has the remaining amount to push). Gecko gets this wrong too
 713             // and pushes to the next page anyway, so not too concerned about it.
 714             setPaginationStrut(result + paginationStrut);
 715             if (childRenderBlock)
 716                 childRenderBlock->setPaginationStrut(0);
 717         } else {
 718             result += paginationStrut;
 719         }
 720     }
 721
 722     if (!unsplittableAdjustmentDelta) {
 723         if (LayoutUnit pageLogicalHeight = pageLogicalHeightForOffset(result)) {
 724             LayoutUnit remainingLogicalHeight = pageRemainingLogicalHeightForOffset(result, ExcludePageBoundary);
 725             LayoutUnit spaceShortage = childLogicalHeight - remainingLogicalHeight;
 726             if (spaceShortage > 0) {
 727                 // If the child crosses a column boundary, report a break, in case nothing inside it
 728                 // has already done so. The column balancer needs to know how much it has to stretch
 729                 // the columns to make more content fit. If no breaks are reported (but do occur),
 730                 // the balancer will have no clue. Only measure the space after the last column
 731                 // boundary, in case it crosses more than one.
 732                 LayoutUnit spaceShortageInLastColumn = intMod(spaceShortage, pageLogicalHeight);
 733                 setPageBreak(result, spaceShortageInLastColumn ? spaceShortageInLastColumn : spaceShortage);
 734             } else if (remainingLogicalHeight == pageLogicalHeight && offsetFromLogicalTopOfFirstPage() + child->logicalTop()) {
 735                 // We're at the very top of a page or column, and it's not the first one. This child
 736                 // may turn out to be the smallest piece of content that causes a page break, so we
 737                 // need to report it.
 738                 setPageBreak(result, childLogicalHeight);
 739             }
 740         }
 741     }
 742
 743     // Similar to how we apply clearance. Go ahead and boost height() to be the place where we're going to position the child.
 744     setLogicalHeight(logicalHeight() + (result - oldTop));
 745
 746     // Return the final adjusted logical top.
 747     return result;
 748 }
 749
 750 void RenderBlockFlow::rebuildFloatsFromIntruding()
 751 {
 752     if (m_floatingObjects)
 753         m_floatingObjects->setHorizontalWritingMode(isHorizontalWritingMode());
 754
 755     HashSet<RenderBox*> oldIntrudingFloatSet;
 756     if (!childrenInline() && m_floatingObjects) {
 757         const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
 758         FloatingObjectSetIterator end = floatingObjectSet.end();
 759         for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
 760             FloatingObject* floatingObject = it->get();
 761             if (!floatingObject->isDescendant())
 762                 oldIntrudingFloatSet.add(floatingObject->renderer());
 763         }
 764     }
 765
 766     // Inline blocks are covered by the isReplaced() check in the avoidFloats method.
 767     if (avoidsFloats() || isDocumentElement() || isRenderView() || isFloatingOrOutOfFlowPositioned() || isTableCell()) {
 768         if (m_floatingObjects) {
 769             m_floatingObjects->clear();
 770         }
 771         if (!oldIntrudingFloatSet.isEmpty())
 772             markAllDescendantsWithFloatsForLayout();
 773         return;
 774     }
 775
 776     RendererToFloatInfoMap floatMap;
 777
 778     if (m_floatingObjects) {
 779         if (childrenInline())
 780             m_floatingObjects->moveAllToFloatInfoMap(floatMap);
 781         else
 782             m_floatingObjects->clear();
 783     }
 784
 785     // We should not process floats if the parent node is not a RenderBlockFlow. Otherwise, we will add
 786     // floats in an invalid context. This will cause a crash arising from a bad cast on the parent.
 787     // See <rdar://problem/8049753>, where float property is applied on a text node in a SVG.
 788     if (!parent() || !parent()->isRenderBlockFlow())
 789         return;
 790
 791     // Attempt to locate a previous sibling with overhanging floats. We skip any elements that
 792     // may have shifted to avoid floats, and any objects whose floats cannot interact with objects
 793     // outside it (i.e. objects that create a new block formatting context).
 794     RenderBlockFlow* parentBlockFlow = toRenderBlockFlow(parent());
 795     bool parentHasFloats = false;
 796     RenderObject* prev = previousSibling();
 797     while (prev && (!prev->isBox() || !prev->isRenderBlock() || toRenderBlock(prev)->avoidsFloats() || toRenderBlock(prev)->createsBlockFormattingContext())) {
 798         if (prev->isFloating())
 799             parentHasFloats = true;
 800         prev = prev->previousSibling();
 801     }
 802
 803     // First add in floats from the parent. Self-collapsing blocks let their parent track any floats that intrude into
 804     // them (as opposed to floats they contain themselves) so check for those here too.
 805     LayoutUnit logicalTopOffset = logicalTop();
 806     bool parentHasIntrudingFloats = !parentHasFloats && (!prev || toRenderBlockFlow(prev)->isSelfCollapsingBlock()) && parentBlockFlow->lowestFloatLogicalBottom() > logicalTopOffset;
 807     if (parentHasFloats || parentHasIntrudingFloats)
 808         addIntrudingFloats(parentBlockFlow, parentBlockFlow->logicalLeftOffsetForContent(), logicalTopOffset);
 809
 810     // Add overhanging floats from the previous RenderBlockFlow, but only if it has a float that intrudes into our space.
 811     if (prev) {
 812         RenderBlockFlow* blockFlow = toRenderBlockFlow(prev);
 813         logicalTopOffset -= blockFlow->logicalTop();
 814         if (blockFlow->lowestFloatLogicalBottom() > logicalTopOffset)
 815             addIntrudingFloats(blockFlow, 0, logicalTopOffset);
 816     }
 817
 818     if (childrenInline()) {
 819         LayoutUnit changeLogicalTop = LayoutUnit::max();
 820         LayoutUnit changeLogicalBottom = LayoutUnit::min();
 821         if (m_floatingObjects) {
 822             const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
 823             FloatingObjectSetIterator end = floatingObjectSet.end();
 824             for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
 825                 FloatingObject* floatingObject = it->get();
 826                 FloatingObject* oldFloatingObject = floatMap.get(floatingObject->renderer());
 827                 LayoutUnit logicalBottom = logicalBottomForFloat(floatingObject);
 828                 if (oldFloatingObject) {
 829                     LayoutUnit oldLogicalBottom = logicalBottomForFloat(oldFloatingObject);
 830                     if (logicalWidthForFloat(floatingObject) != logicalWidthForFloat(oldFloatingObject) || logicalLeftForFloat(floatingObject) != logicalLeftForFloat(oldFloatingObject)) {
 831                         changeLogicalTop = 0;
 832                         changeLogicalBottom = max(changeLogicalBottom, max(logicalBottom, oldLogicalBottom));
 833                     } else {
 834                         if (logicalBottom != oldLogicalBottom) {
 835                             changeLogicalTop = min(changeLogicalTop, min(logicalBottom, oldLogicalBottom));
 836                             changeLogicalBottom = max(changeLogicalBottom, max(logicalBottom, oldLogicalBottom));
 837                         }
 838                         LayoutUnit logicalTop = logicalTopForFloat(floatingObject);
 839                         LayoutUnit oldLogicalTop = logicalTopForFloat(oldFloatingObject);
 840                         if (logicalTop != oldLogicalTop) {
 841                             changeLogicalTop = min(changeLogicalTop, min(logicalTop, oldLogicalTop));
 842                             changeLogicalBottom = max(changeLogicalBottom, max(logicalTop, oldLogicalTop));
 843                         }
 844                     }
 845
 846                     if (oldFloatingObject->originatingLine() && !selfNeedsLayout()) {
 847                         ASSERT(oldFloatingObject->originatingLine()->renderer() == this);
 848                         oldFloatingObject->originatingLine()->markDirty();
 849                     }
 850
 851                     floatMap.remove(floatingObject->renderer());
 852                 } else {
 853                     changeLogicalTop = 0;
 854                     changeLogicalBottom = max(changeLogicalBottom, logicalBottom);
 855                 }
 856             }
 857         }
 858
 859         RendererToFloatInfoMap::iterator end = floatMap.end();
 860         for (RendererToFloatInfoMap::iterator it = floatMap.begin(); it != end; ++it) {
 861             OwnPtr<FloatingObject>& floatingObject = it->value;
 862             if (!floatingObject->isDescendant()) {
 863                 changeLogicalTop = 0;
 864                 changeLogicalBottom = max(changeLogicalBottom, logicalBottomForFloat(floatingObject.get()));
 865             }
 866         }
 867
 868         markLinesDirtyInBlockRange(changeLogicalTop, changeLogicalBottom);
 869     } else if (!oldIntrudingFloatSet.isEmpty()) {
 870         // If there are previously intruding floats that no longer intrude, then children with floats
 871         // should also get layout because they might need their floating object lists cleared.
 872         if (m_floatingObjects->set().size() < oldIntrudingFloatSet.size()) {
 873             markAllDescendantsWithFloatsForLayout();
 874         } else {
 875             const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
 876             FloatingObjectSetIterator end = floatingObjectSet.end();
 877             for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end && !oldIntrudingFloatSet.isEmpty(); ++it)
 878                 oldIntrudingFloatSet.remove((*it)->renderer());
 879             if (!oldIntrudingFloatSet.isEmpty())
 880                 markAllDescendantsWithFloatsForLayout();
 881         }
 882     }
 883 }
 884
 885 void RenderBlockFlow::layoutBlockChildren(bool relayoutChildren, SubtreeLayoutScope& layoutScope, LayoutUnit beforeEdge, LayoutUnit afterEdge)
 886 {
 887     dirtyForLayoutFromPercentageHeightDescendants(layoutScope);
 888
 889     // The margin struct caches all our current margin collapsing state. The compact struct caches state when we encounter compacts,
 890     MarginInfo marginInfo(this, beforeEdge, afterEdge);
 891
 892     // Fieldsets need to find their legend and position it inside the border of the object.
 893     // The legend then gets skipped during normal layout. The same is true for ruby text.
 894     // It doesn't get included in the normal layout process but is instead skipped.
 895     RenderObject* childToExclude = layoutSpecialExcludedChild(relayoutChildren, layoutScope);
 896
 897     LayoutUnit previousFloatLogicalBottom = 0;
 898
 899     RenderBox* next = firstChildBox();
 900     RenderBox* lastNormalFlowChild = 0;
 901
 902     while (next) {
 903         RenderBox* child = next;
 904         next = child->nextSiblingBox();
 905
 906         // FIXME: this should only be set from clearNeedsLayout crbug.com/361250
 907         child->setLayoutDidGetCalled(true);
 908
 909         if (childToExclude == child)
 910             continue; // Skip this child, since it will be positioned by the specialized subclass (fieldsets and ruby runs).
 911
 912         updateBlockChildDirtyBitsBeforeLayout(relayoutChildren, child);
 913
 914         if (child->isOutOfFlowPositioned()) {
 915             child->containingBlock()->insertPositionedObject(child);
 916             adjustPositionedBlock(child, marginInfo);
 917             continue;
 918         }
 919         if (child->isFloating()) {
 920             insertFloatingObject(child);
 921             adjustFloatingBlock(marginInfo);
 922             continue;
 923         }
 924
 925         // Lay out the child.
 926         layoutBlockChild(child, marginInfo, previousFloatLogicalBottom);
 927         lastNormalFlowChild = child;
 928     }
 929
 930     // Now do the handling of the bottom of the block, adding in our bottom border/padding and
 931     // determining the correct collapsed bottom margin information.
 932     handleAfterSideOfBlock(lastNormalFlowChild, beforeEdge, afterEdge, marginInfo);
 933 }
 934
 935 // Our MarginInfo state used when laying out block children.
 936 MarginInfo::MarginInfo(RenderBlockFlow* blockFlow, LayoutUnit beforeBorderPadding, LayoutUnit afterBorderPadding)
 937     : m_canCollapseMarginAfterWithLastChild(true)
 938     , m_atBeforeSideOfBlock(true)
 939     , m_atAfterSideOfBlock(false)
 940     , m_hasMarginBeforeQuirk(false)
 941     , m_hasMarginAfterQuirk(false)
 942     , m_determinedMarginBeforeQuirk(false)
 943     , m_discardMargin(false)
 944 {
 945     RenderStyle* blockStyle = blockFlow->style();
 946     ASSERT(blockFlow->isRenderView() || blockFlow->parent());
 947     m_canCollapseWithChildren = !blockFlow->createsBlockFormattingContext() && !blockFlow->isRenderFlowThread() && !blockFlow->isRenderView();
 948
 949     m_canCollapseMarginBeforeWithChildren = m_canCollapseWithChildren && !beforeBorderPadding && blockStyle->marginBeforeCollapse() != MSEPARATE;
 950
 951     // If any height other than auto is specified in CSS, then we don't collapse our bottom
 952     // margins with our children's margins. To do otherwise would be to risk odd visual
 953     // effects when the children overflow out of the parent block and yet still collapse
 954     // with it. We also don't collapse if we have any bottom border/padding.
 955     m_canCollapseMarginAfterWithChildren = m_canCollapseWithChildren && !afterBorderPadding
 956         && (blockStyle->logicalHeight().isAuto() && !blockStyle->logicalHeight().value()) && blockStyle->marginAfterCollapse() != MSEPARATE;
 957
 958     m_quirkContainer = blockFlow->isTableCell() || blockFlow->isBody();
 959
 960     m_discardMargin = m_canCollapseMarginBeforeWithChildren && blockFlow->mustDiscardMarginBefore();
 961
 962     m_positiveMargin = (m_canCollapseMarginBeforeWithChildren && !blockFlow->mustDiscardMarginBefore()) ? blockFlow->maxPositiveMarginBefore() : LayoutUnit();
 963     m_negativeMargin = (m_canCollapseMarginBeforeWithChildren && !blockFlow->mustDiscardMarginBefore()) ? blockFlow->maxNegativeMarginBefore() : LayoutUnit();
 964 }
 965
 966 RenderBlockFlow::MarginValues RenderBlockFlow::marginValuesForChild(RenderBox* child) const
 967 {
 968     LayoutUnit childBeforePositive = 0;
 969     LayoutUnit childBeforeNegative = 0;
 970     LayoutUnit childAfterPositive = 0;
 971     LayoutUnit childAfterNegative = 0;
 972
 973     LayoutUnit beforeMargin = 0;
 974     LayoutUnit afterMargin = 0;
 975
 976     RenderBlockFlow* childRenderBlockFlow = child->isRenderBlockFlow() ? toRenderBlockFlow(child) : 0;
 977
 978     // If the child has the same directionality as we do, then we can just return its
 979     // margins in the same direction.
 980     if (!child->isWritingModeRoot()) {
 981         if (childRenderBlockFlow) {
 982             childBeforePositive = childRenderBlockFlow->maxPositiveMarginBefore();
 983             childBeforeNegative = childRenderBlockFlow->maxNegativeMarginBefore();
 984             childAfterPositive = childRenderBlockFlow->maxPositiveMarginAfter();
 985             childAfterNegative = childRenderBlockFlow->maxNegativeMarginAfter();
 986         } else {
 987             beforeMargin = child->marginBefore();
 988             afterMargin = child->marginAfter();
 989         }
 990     } else if (child->isHorizontalWritingMode() == isHorizontalWritingMode()) {
 991         // The child has a different directionality. If the child is parallel, then it's just
 992         // flipped relative to us. We can use the margins for the opposite edges.
 993         if (childRenderBlockFlow) {
 994             childBeforePositive = childRenderBlockFlow->maxPositiveMarginAfter();
 995             childBeforeNegative = childRenderBlockFlow->maxNegativeMarginAfter();
 996             childAfterPositive = childRenderBlockFlow->maxPositiveMarginBefore();
 997             childAfterNegative = childRenderBlockFlow->maxNegativeMarginBefore();
 998         } else {
 999             beforeMargin = child->marginAfter();
1000             afterMargin = child->marginBefore();
1001         }
1002     } else {
1003         // The child is perpendicular to us, which means its margins don't collapse but are on the
1004         // "logical left/right" sides of the child box. We can just return the raw margin in this case.
1005         beforeMargin = marginBeforeForChild(child);
1006         afterMargin = marginAfterForChild(child);
1007     }
1008
1009     // Resolve uncollapsing margins into their positive/negative buckets.
1010     if (beforeMargin) {
1011         if (beforeMargin > 0)
1012             childBeforePositive = beforeMargin;
1013         else
1014             childBeforeNegative = -beforeMargin;
1015     }
1016     if (afterMargin) {
1017         if (afterMargin > 0)
1018             childAfterPositive = afterMargin;
1019         else
1020             childAfterNegative = -afterMargin;
1021     }
1022
1023     return RenderBlockFlow::MarginValues(childBeforePositive, childBeforeNegative, childAfterPositive, childAfterNegative);
1024 }
1025
1026 LayoutUnit RenderBlockFlow::collapseMargins(RenderBox* child, MarginInfo& marginInfo, bool childIsSelfCollapsing)
1027 {
1028     bool childDiscardMarginBefore = mustDiscardMarginBeforeForChild(child);
1029     bool childDiscardMarginAfter = mustDiscardMarginAfterForChild(child);
1030
1031     // The child discards the before margin when the the after margin has discard in the case of a self collapsing block.
1032     childDiscardMarginBefore = childDiscardMarginBefore || (childDiscardMarginAfter && childIsSelfCollapsing);
1033
1034     // Get the four margin values for the child and cache them.
1035     const RenderBlockFlow::MarginValues childMargins = marginValuesForChild(child);
1036
1037     // Get our max pos and neg top margins.
1038     LayoutUnit posTop = childMargins.positiveMarginBefore();
1039     LayoutUnit negTop = childMargins.negativeMarginBefore();
1040
1041     // For self-collapsing blocks, collapse our bottom margins into our
1042     // top to get new posTop and negTop values.
1043     if (childIsSelfCollapsing) {
1044         posTop = max(posTop, childMargins.positiveMarginAfter());
1045         negTop = max(negTop, childMargins.negativeMarginAfter());
1046     }
1047
1048     // See if the top margin is quirky. We only care if this child has
1049     // margins that will collapse with us.
1050     bool topQuirk = hasMarginBeforeQuirk(child);
1051
1052     if (marginInfo.canCollapseWithMarginBefore()) {
1053         if (!childDiscardMarginBefore && !marginInfo.discardMargin()) {
1054             // This child is collapsing with the top of the
1055             // block. If it has larger margin values, then we need to update
1056             // our own maximal values.
1057             if (!document().inQuirksMode() || !marginInfo.quirkContainer() || !topQuirk)
1058                 setMaxMarginBeforeValues(max(posTop, maxPositiveMarginBefore()), max(negTop, maxNegativeMarginBefore()));
1059
1060             // The minute any of the margins involved isn't a quirk, don't
1061             // collapse it away, even if the margin is smaller (www.webreference.com
1062             // has an example of this, a <dt> with 0.8em author-specified inside
1063             // a <dl> inside a <td>.
1064             if (!marginInfo.determinedMarginBeforeQuirk() && !topQuirk && (posTop - negTop)) {
1065                 setHasMarginBeforeQuirk(false);
1066                 marginInfo.setDeterminedMarginBeforeQuirk(true);
1067             }
1068
1069             if (!marginInfo.determinedMarginBeforeQuirk() && topQuirk && !marginBefore()) {
1070                 // We have no top margin and our top child has a quirky margin.
1071                 // We will pick up this quirky margin and pass it through.
1072                 // This deals with the <td><div><p> case.
1073                 // Don't do this for a block that split two inlines though. You do
1074                 // still apply margins in this case.
1075                 setHasMarginBeforeQuirk(true);
1076             }
1077         } else {
1078             // The before margin of the container will also discard all the margins it is collapsing with.
1079             setMustDiscardMarginBefore();
1080         }
1081     }
1082
1083     // Once we find a child with discardMarginBefore all the margins collapsing with us must also discard.
1084     if (childDiscardMarginBefore) {
1085         marginInfo.setDiscardMargin(true);
1086         marginInfo.clearMargin();
1087     }
1088
1089     if (marginInfo.quirkContainer() && marginInfo.atBeforeSideOfBlock() && (posTop - negTop))
1090         marginInfo.setHasMarginBeforeQuirk(topQuirk);
1091
1092     LayoutUnit beforeCollapseLogicalTop = logicalHeight();
1093     LayoutUnit logicalTop = beforeCollapseLogicalTop;
1094
1095     LayoutUnit clearanceForSelfCollapsingBlock;
1096     RenderObject* prev = child->previousSibling();
1097     RenderBlockFlow* previousBlockFlow =  prev && prev->isRenderBlockFlow() && !prev->isFloatingOrOutOfFlowPositioned() ? toRenderBlockFlow(prev) : 0;
1098     // If the child's previous sibling is a self-collapsing block that cleared a float then its top border edge has been set at the bottom border edge
1099     // of the float. Since we want to collapse the child's top margin with the self-collapsing block's top and bottom margins we need to adjust our parent's height to match the
1100     // margin top of the self-collapsing block. If the resulting collapsed margin leaves the child still intruding into the float then we will want to clear it.
1101     if (!marginInfo.canCollapseWithMarginBefore() && previousBlockFlow && previousBlockFlow->isSelfCollapsingBlock()) {
1102         clearanceForSelfCollapsingBlock = previousBlockFlow->marginOffsetForSelfCollapsingBlock();
1103         setLogicalHeight(logicalHeight() - clearanceForSelfCollapsingBlock);
1104     }
1105
1106     if (childIsSelfCollapsing) {
1107         // For a self collapsing block both the before and after margins get discarded. The block doesn't contribute anything to the height of the block.
1108         // Also, the child's top position equals the logical height of the container.
1109         if (!childDiscardMarginBefore && !marginInfo.discardMargin()) {
1110             // This child has no height. We need to compute our
1111             // position before we collapse the child's margins together,
1112             // so that we can get an accurate position for the zero-height block.
1113             LayoutUnit collapsedBeforePos = max(marginInfo.positiveMargin(), childMargins.positiveMarginBefore());
1114             LayoutUnit collapsedBeforeNeg = max(marginInfo.negativeMargin(), childMargins.negativeMarginBefore());
1115             marginInfo.setMargin(collapsedBeforePos, collapsedBeforeNeg);
1116
1117             // Now collapse the child's margins together, which means examining our
1118             // bottom margin values as well.
1119             marginInfo.setPositiveMarginIfLarger(childMargins.positiveMarginAfter());
1120             marginInfo.setNegativeMarginIfLarger(childMargins.negativeMarginAfter());
1121
1122             if (!marginInfo.canCollapseWithMarginBefore()) {
1123                 // We need to make sure that the position of the self-collapsing block
1124                 // is correct, since it could have overflowing content
1125                 // that needs to be positioned correctly (e.g., a block that
1126                 // had a specified height of 0 but that actually had subcontent).
1127                 logicalTop = logicalHeight() + collapsedBeforePos - collapsedBeforeNeg;
1128             }
1129         }
1130     } else {
1131         if (mustSeparateMarginBeforeForChild(child)) {
1132             ASSERT(!marginInfo.discardMargin() || (marginInfo.discardMargin() && !marginInfo.margin()));
1133             // If we are at the before side of the block and we collapse, ignore the computed margin
1134             // and just add the child margin to the container height. This will correctly position
1135             // the child inside the container.
1136             LayoutUnit separateMargin = !marginInfo.canCollapseWithMarginBefore() ? marginInfo.margin() : LayoutUnit(0);
1137             setLogicalHeight(logicalHeight() + separateMargin + marginBeforeForChild(child));
1138             logicalTop = logicalHeight();
1139         } else if (!marginInfo.discardMargin() && (!marginInfo.atBeforeSideOfBlock()
1140             || (!marginInfo.canCollapseMarginBeforeWithChildren()
1141             && (!document().inQuirksMode() || !marginInfo.quirkContainer() || !marginInfo.hasMarginBeforeQuirk())))) {
1142             // We're collapsing with a previous sibling's margins and not
1143             // with the top of the block.
1144             setLogicalHeight(logicalHeight() + max(marginInfo.positiveMargin(), posTop) - max(marginInfo.negativeMargin(), negTop));
1145             logicalTop = logicalHeight();
1146         }
1147
1148         marginInfo.setDiscardMargin(childDiscardMarginAfter);
1149
1150         if (!marginInfo.discardMargin()) {
1151             marginInfo.setPositiveMargin(childMargins.positiveMarginAfter());
1152             marginInfo.setNegativeMargin(childMargins.negativeMarginAfter());
1153         } else {
1154             marginInfo.clearMargin();
1155         }
1156
1157         if (marginInfo.margin())
1158             marginInfo.setHasMarginAfterQuirk(hasMarginAfterQuirk(child));
1159     }
1160
1161     // If margins would pull us past the top of the next page, then we need to pull back and pretend like the margins
1162     // collapsed into the page edge.
1163     LayoutState* layoutState = view()->layoutState();
1164     if (layoutState->isPaginated() && layoutState->pageLogicalHeight() && logicalTop > beforeCollapseLogicalTop) {
1165         LayoutUnit oldLogicalTop = logicalTop;
1166         logicalTop = min(logicalTop, nextPageLogicalTop(beforeCollapseLogicalTop));
1167         setLogicalHeight(logicalHeight() + (logicalTop - oldLogicalTop));
1168     }
1169
1170     if (previousBlockFlow) {
1171         // If |child| is a self-collapsing block it may have collapsed into a previous sibling and although it hasn't reduced the height of the parent yet
1172         // any floats from the parent will now overhang.
1173         LayoutUnit oldLogicalHeight = logicalHeight();
1174         setLogicalHeight(logicalTop);
1175         if (!previousBlockFlow->avoidsFloats() && (previousBlockFlow->logicalTop() + previousBlockFlow->lowestFloatLogicalBottom()) > logicalTop)
1176             addOverhangingFloats(previousBlockFlow, false);
1177         setLogicalHeight(oldLogicalHeight);
1178
1179         // If |child|'s previous sibling is a self-collapsing block that cleared a float and margin collapsing resulted in |child| moving up
1180         // into the margin area of the self-collapsing block then the float it clears is now intruding into |child|. Layout again so that we can look for
1181         // floats in the parent that overhang |child|'s new logical top.
1182         bool logicalTopIntrudesIntoFloat = clearanceForSelfCollapsingBlock > 0 && logicalTop < beforeCollapseLogicalTop;
1183         if (logicalTopIntrudesIntoFloat && containsFloats() && !child->avoidsFloats() && lowestFloatLogicalBottom() > logicalTop)
1184             child->setNeedsLayoutAndFullPaintInvalidation();
1185     }
1186
1187     return logicalTop;
1188 }
1189
1190 void RenderBlockFlow::adjustPositionedBlock(RenderBox* child, const MarginInfo& marginInfo)
1191 {
1192     bool isHorizontal = isHorizontalWritingMode();
1193     bool hasStaticBlockPosition = child->style()->hasStaticBlockPosition(isHorizontal);
1194
1195     LayoutUnit logicalTop = logicalHeight();
1196     updateStaticInlinePositionForChild(child, logicalTop);
1197
1198     if (!marginInfo.canCollapseWithMarginBefore()) {
1199         // Positioned blocks don't collapse margins, so add the margin provided by
1200         // the container now. The child's own margin is added later when calculating its logical top.
1201         LayoutUnit collapsedBeforePos = marginInfo.positiveMargin();
1202         LayoutUnit collapsedBeforeNeg = marginInfo.negativeMargin();
1203         logicalTop += collapsedBeforePos - collapsedBeforeNeg;
1204     }
1205
1206     RenderLayer* childLayer = child->layer();
1207     if (childLayer->staticBlockPosition() != logicalTop) {
1208         childLayer->setStaticBlockPosition(logicalTop);
1209         if (hasStaticBlockPosition)
1210             child->setChildNeedsLayout(MarkOnlyThis);
1211     }
1212 }
1213
1214 LayoutUnit RenderBlockFlow::computeStartPositionDeltaForChildAvoidingFloats(const RenderBox* child, LayoutUnit childMarginStart)
1215 {
1216     LayoutUnit startPosition = startOffsetForContent();
1217
1218     // Add in our start margin.
1219     LayoutUnit oldPosition = startPosition + childMarginStart;
1220     LayoutUnit newPosition = oldPosition;
1221
1222     LayoutUnit blockOffset = logicalTopForChild(child);
1223     LayoutUnit startOff = startOffsetForLine(blockOffset, false, logicalHeightForChild(child));
1224
1225     if (style()->textAlign() != WEBKIT_CENTER && !child->style()->marginStartUsing(style()).isAuto()) {
1226         if (childMarginStart < 0)
1227             startOff += childMarginStart;
1228         newPosition = max(newPosition, startOff); // Let the float sit in the child's margin if it can fit.
1229     } else if (startOff != startPosition) {
1230         newPosition = startOff + childMarginStart;
1231     }
1232
1233     return newPosition - oldPosition;
1234 }
1235
1236 LayoutUnit RenderBlockFlow::clearFloatsIfNeeded(RenderBox* child, MarginInfo& marginInfo, LayoutUnit oldTopPosMargin, LayoutUnit oldTopNegMargin, LayoutUnit yPos, bool childIsSelfCollapsing)
1237 {
1238     LayoutUnit heightIncrease = getClearDelta(child, yPos);
1239     if (!heightIncrease)
1240         return yPos;
1241
1242     if (childIsSelfCollapsing) {
1243         bool childDiscardMargin = mustDiscardMarginBeforeForChild(child) || mustDiscardMarginAfterForChild(child);
1244
1245         // For self-collapsing blocks that clear, they can still collapse their
1246         // margins with following siblings. Reset the current margins to represent
1247         // the self-collapsing block's margins only.
1248         // If DISCARD is specified for -webkit-margin-collapse, reset the margin values.
1249         RenderBlockFlow::MarginValues childMargins = marginValuesForChild(child);
1250         if (!childDiscardMargin) {
1251             marginInfo.setPositiveMargin(max(childMargins.positiveMarginBefore(), childMargins.positiveMarginAfter()));
1252             marginInfo.setNegativeMargin(max(childMargins.negativeMarginBefore(), childMargins.negativeMarginAfter()));
1253         } else {
1254             marginInfo.clearMargin();
1255         }
1256         marginInfo.setDiscardMargin(childDiscardMargin);
1257
1258         // CSS2.1 states:
1259         // "If the top and bottom margins of an element with clearance are adjoining, its margins collapse with
1260         // the adjoining margins of following siblings but that resulting margin does not collapse with the bottom margin of the parent block."
1261         // So the parent's bottom margin cannot collapse through this block or any subsequent self-collapsing blocks. Set a bit to ensure
1262         // this happens; it will get reset if we encounter an in-flow sibling that is not self-collapsing.
1263         marginInfo.setCanCollapseMarginAfterWithLastChild(false);
1264
1265         // For now set the border-top of |child| flush with the bottom border-edge of the float so it can layout any floating or positioned children of
1266         // its own at the correct vertical position. If subsequent siblings attempt to collapse with |child|'s margins in |collapseMargins| we will
1267         // adjust the height of the parent to |child|'s margin top (which if it is positive sits up 'inside' the float it's clearing) so that all three
1268         // margins can collapse at the correct vertical position.
1269         // Per CSS2.1 we need to ensure that any negative margin-top clears |child| beyond the bottom border-edge of the float so that the top border edge of the child
1270         // (i.e. its clearance)  is at a position that satisfies the equation: "the amount of clearance is set so that clearance + margin-top = [height of float],
1271         // i.e., clearance = [height of float] - margin-top".
1272         setLogicalHeight(child->logicalTop() + childMargins.negativeMarginBefore());
1273     } else {
1274         // Increase our height by the amount we had to clear.
1275         setLogicalHeight(logicalHeight() + heightIncrease);
1276     }
1277
1278     if (marginInfo.canCollapseWithMarginBefore()) {
1279         // We can no longer collapse with the top of the block since a clear
1280         // occurred. The empty blocks collapse into the cleared block.
1281         setMaxMarginBeforeValues(oldTopPosMargin, oldTopNegMargin);
1282         marginInfo.setAtBeforeSideOfBlock(false);
1283
1284         // In case the child discarded the before margin of the block we need to reset the mustDiscardMarginBefore flag to the initial value.
1285         setMustDiscardMarginBefore(style()->marginBeforeCollapse() == MDISCARD);
1286     }
1287
1288     return yPos + heightIncrease;
1289 }
1290
1291 void RenderBlockFlow::setCollapsedBottomMargin(const MarginInfo& marginInfo)
1292 {
1293     if (marginInfo.canCollapseWithMarginAfter() && !marginInfo.canCollapseWithMarginBefore()) {
1294         // Update the after side margin of the container to discard if the after margin of the last child also discards and we collapse with it.
1295         // Don't update the max margin values because we won't need them anyway.
1296         if (marginInfo.discardMargin()) {
1297             setMustDiscardMarginAfter();
1298             return;
1299         }
1300
1301         // Update our max pos/neg bottom margins, since we collapsed our bottom margins
1302         // with our children.
1303         setMaxMarginAfterValues(max(maxPositiveMarginAfter(), marginInfo.positiveMargin()), max(maxNegativeMarginAfter(), marginInfo.negativeMargin()));
1304
1305         if (!marginInfo.hasMarginAfterQuirk())
1306             setHasMarginAfterQuirk(false);
1307
1308         if (marginInfo.hasMarginAfterQuirk() && !marginAfter()) {
1309             // We have no bottom margin and our last child has a quirky margin.
1310             // We will pick up this quirky margin and pass it through.
1311             // This deals with the <td><div><p> case.
1312             setHasMarginAfterQuirk(true);
1313         }
1314     }
1315 }
1316
1317 void RenderBlockFlow::marginBeforeEstimateForChild(RenderBox* child, LayoutUnit& positiveMarginBefore, LayoutUnit& negativeMarginBefore, bool& discardMarginBefore) const
1318 {
1319     // Give up if in quirks mode and we're a body/table cell and the top margin of the child box is quirky.
1320     // Give up if the child specified -webkit-margin-collapse: separate that prevents collapsing.
1321     // FIXME: Use writing mode independent accessor for marginBeforeCollapse.
1322     if ((document().inQuirksMode() && hasMarginBeforeQuirk(child) && (isTableCell() || isBody())) || child->style()->marginBeforeCollapse() == MSEPARATE)
1323         return;
1324
1325     // The margins are discarded by a child that specified -webkit-margin-collapse: discard.
1326     // FIXME: Use writing mode independent accessor for marginBeforeCollapse.
1327     if (child->style()->marginBeforeCollapse() == MDISCARD) {
1328         positiveMarginBefore = 0;
1329         negativeMarginBefore = 0;
1330         discardMarginBefore = true;
1331         return;
1332     }
1333
1334     LayoutUnit beforeChildMargin = marginBeforeForChild(child);
1335     positiveMarginBefore = max(positiveMarginBefore, beforeChildMargin);
1336     negativeMarginBefore = max(negativeMarginBefore, -beforeChildMargin);
1337
1338     if (!child->isRenderBlockFlow())
1339         return;
1340
1341     RenderBlockFlow* childBlockFlow = toRenderBlockFlow(child);
1342     if (childBlockFlow->childrenInline() || childBlockFlow->isWritingModeRoot())
1343         return;
1344
1345     MarginInfo childMarginInfo(childBlockFlow, childBlockFlow->borderBefore() + childBlockFlow->paddingBefore(), childBlockFlow->borderAfter() + childBlockFlow->paddingAfter());
1346     if (!childMarginInfo.canCollapseMarginBeforeWithChildren())
1347         return;
1348
1349     RenderBox* grandchildBox = childBlockFlow->firstChildBox();
1350     for ( ; grandchildBox; grandchildBox = grandchildBox->nextSiblingBox()) {
1351         if (!grandchildBox->isFloatingOrOutOfFlowPositioned())
1352             break;
1353     }
1354
1355     // Give up if there is clearance on the box, since it probably won't collapse into us.
1356     if (!grandchildBox || grandchildBox->style()->clear() != CNONE)
1357         return;
1358
1359     // Make sure to update the block margins now for the grandchild box so that we're looking at current values.
1360     if (grandchildBox->needsLayout()) {
1361         grandchildBox->computeAndSetBlockDirectionMargins(this);
1362         if (grandchildBox->isRenderBlock()) {
1363             RenderBlock* grandchildBlock = toRenderBlock(grandchildBox);
1364             grandchildBlock->setHasMarginBeforeQuirk(grandchildBox->style()->hasMarginBeforeQuirk());
1365             grandchildBlock->setHasMarginAfterQuirk(grandchildBox->style()->hasMarginAfterQuirk());
1366         }
1367     }
1368
1369     // Collapse the margin of the grandchild box with our own to produce an estimate.
1370     childBlockFlow->marginBeforeEstimateForChild(grandchildBox, positiveMarginBefore, negativeMarginBefore, discardMarginBefore);
1371 }
1372
1373 LayoutUnit RenderBlockFlow::estimateLogicalTopPosition(RenderBox* child, const MarginInfo& marginInfo, LayoutUnit& estimateWithoutPagination)
1374 {
1375     // FIXME: We need to eliminate the estimation of vertical position, because when it's wrong we sometimes trigger a pathological
1376     // relayout if there are intruding floats.
1377     LayoutUnit logicalTopEstimate = logicalHeight();
1378     if (!marginInfo.canCollapseWithMarginBefore()) {
1379         LayoutUnit positiveMarginBefore = 0;
1380         LayoutUnit negativeMarginBefore = 0;
1381         bool discardMarginBefore = false;
1382         if (child->selfNeedsLayout()) {
1383             // Try to do a basic estimation of how the collapse is going to go.
1384             marginBeforeEstimateForChild(child, positiveMarginBefore, negativeMarginBefore, discardMarginBefore);
1385         } else {
1386             // Use the cached collapsed margin values from a previous layout. Most of the time they
1387             // will be right.
1388             RenderBlockFlow::MarginValues marginValues = marginValuesForChild(child);
1389             positiveMarginBefore = max(positiveMarginBefore, marginValues.positiveMarginBefore());
1390             negativeMarginBefore = max(negativeMarginBefore, marginValues.negativeMarginBefore());
1391             discardMarginBefore = mustDiscardMarginBeforeForChild(child);
1392         }
1393
1394         // Collapse the result with our current margins.
1395         if (!discardMarginBefore)
1396             logicalTopEstimate += max(marginInfo.positiveMargin(), positiveMarginBefore) - max(marginInfo.negativeMargin(), negativeMarginBefore);
1397     }
1398
1399     // Adjust logicalTopEstimate down to the next page if the margins are so large that we don't fit on the current
1400     // page.
1401     LayoutState* layoutState = view()->layoutState();
1402     if (layoutState->isPaginated() && layoutState->pageLogicalHeight() && logicalTopEstimate > logicalHeight())
1403         logicalTopEstimate = min(logicalTopEstimate, nextPageLogicalTop(logicalHeight()));
1404
1405     logicalTopEstimate += getClearDelta(child, logicalTopEstimate);
1406
1407     estimateWithoutPagination = logicalTopEstimate;
1408
1409     if (layoutState->isPaginated()) {
1410         // If the object has a page or column break value of "before", then we should shift to the top of the next page.
1411         logicalTopEstimate = applyBeforeBreak(child, logicalTopEstimate);
1412
1413         // For replaced elements and scrolled elements, we want to shift them to the next page if they don't fit on the current one.
1414         logicalTopEstimate = adjustForUnsplittableChild(child, logicalTopEstimate);
1415
1416         if (!child->selfNeedsLayout() && child->isRenderBlock())
1417             logicalTopEstimate += toRenderBlock(child)->paginationStrut();
1418     }
1419
1420     return logicalTopEstimate;
1421 }
1422
1423 LayoutUnit RenderBlockFlow::marginOffsetForSelfCollapsingBlock()
1424 {
1425     ASSERT(isSelfCollapsingBlock());
1426     RenderBlockFlow* parentBlock = toRenderBlockFlow(parent());
1427     if (parentBlock && style()->clear() && parentBlock->getClearDelta(this, logicalHeight()))
1428         return marginValuesForChild(this).positiveMarginBefore();
1429     return LayoutUnit();
1430 }
1431
1432 void RenderBlockFlow::adjustFloatingBlock(const MarginInfo& marginInfo)
1433 {
1434     // The float should be positioned taking into account the bottom margin
1435     // of the previous flow. We add that margin into the height, get the
1436     // float positioned properly, and then subtract the margin out of the
1437     // height again. In the case of self-collapsing blocks, we always just
1438     // use the top margins, since the self-collapsing block collapsed its
1439     // own bottom margin into its top margin.
1440     //
1441     // Note also that the previous flow may collapse its margin into the top of
1442     // our block. If this is the case, then we do not add the margin in to our
1443     // height when computing the position of the float. This condition can be tested
1444     // for by simply calling canCollapseWithMarginBefore. See
1445     // http://www.hixie.ch/tests/adhoc/css/box/block/margin-collapse/046.html for
1446     // an example of this scenario.
1447     LayoutUnit marginOffset = marginInfo.canCollapseWithMarginBefore() ? LayoutUnit() : marginInfo.margin();
1448     setLogicalHeight(logicalHeight() + marginOffset);
1449     positionNewFloats();
1450     setLogicalHeight(logicalHeight() - marginOffset);
1451 }
1452
1453 void RenderBlockFlow::handleAfterSideOfBlock(RenderBox* lastChild, LayoutUnit beforeSide, LayoutUnit afterSide, MarginInfo& marginInfo)
1454 {
1455     marginInfo.setAtAfterSideOfBlock(true);
1456
1457     // If our last child was a self-collapsing block with clearance then our logical height is flush with the
1458     // bottom edge of the float that the child clears. The correct vertical position for the margin-collapsing we want
1459     // to perform now is at the child's margin-top - so adjust our height to that position.
1460     if (lastChild && lastChild->isRenderBlockFlow() && lastChild->isSelfCollapsingBlock())
1461         setLogicalHeight(logicalHeight() - toRenderBlockFlow(lastChild)->marginOffsetForSelfCollapsingBlock());
1462
1463     if (marginInfo.canCollapseMarginAfterWithChildren() && !marginInfo.canCollapseMarginAfterWithLastChild())
1464         marginInfo.setCanCollapseMarginAfterWithChildren(false);
1465
1466     // If we can't collapse with children then go ahead and add in the bottom margin.
1467     if (!marginInfo.discardMargin() && (!marginInfo.canCollapseWithMarginAfter() && !marginInfo.canCollapseWithMarginBefore()
1468         && (!document().inQuirksMode() || !marginInfo.quirkContainer() || !marginInfo.hasMarginAfterQuirk())))
1469         setLogicalHeight(logicalHeight() + marginInfo.margin());
1470
1471     // Now add in our bottom border/padding.
1472     setLogicalHeight(logicalHeight() + afterSide);
1473
1474     // Negative margins can cause our height to shrink below our minimal height (border/padding).
1475     // If this happens, ensure that the computed height is increased to the minimal height.
1476     setLogicalHeight(max(logicalHeight(), beforeSide + afterSide));
1477
1478     // Update our bottom collapsed margin info.
1479     setCollapsedBottomMargin(marginInfo);
1480 }
1481
1482 void RenderBlockFlow::setMustDiscardMarginBefore(bool value)
1483 {
1484     if (style()->marginBeforeCollapse() == MDISCARD) {
1485         ASSERT(value);
1486         return;
1487     }
1488
1489     if (!m_rareData && !value)
1490         return;
1491
1492     if (!m_rareData)
1493         m_rareData = adoptPtr(new RenderBlockFlowRareData(this));
1494
1495     m_rareData->m_discardMarginBefore = value;
1496 }
1497
1498 void RenderBlockFlow::setMustDiscardMarginAfter(bool value)
1499 {
1500     if (style()->marginAfterCollapse() == MDISCARD) {
1501         ASSERT(value);
1502         return;
1503     }
1504
1505     if (!m_rareData && !value)
1506         return;
1507
1508     if (!m_rareData)
1509         m_rareData = adoptPtr(new RenderBlockFlowRareData(this));
1510
1511     m_rareData->m_discardMarginAfter = value;
1512 }
1513
1514 bool RenderBlockFlow::mustDiscardMarginBefore() const
1515 {
1516     return style()->marginBeforeCollapse() == MDISCARD || (m_rareData && m_rareData->m_discardMarginBefore);
1517 }
1518
1519 bool RenderBlockFlow::mustDiscardMarginAfter() const
1520 {
1521     return style()->marginAfterCollapse() == MDISCARD || (m_rareData && m_rareData->m_discardMarginAfter);
1522 }
1523
1524 bool RenderBlockFlow::mustDiscardMarginBeforeForChild(const RenderBox* child) const
1525 {
1526     ASSERT(!child->selfNeedsLayout());
1527     if (!child->isWritingModeRoot())
1528         return child->isRenderBlockFlow() ? toRenderBlockFlow(child)->mustDiscardMarginBefore() : (child->style()->marginBeforeCollapse() == MDISCARD);
1529     if (child->isHorizontalWritingMode() == isHorizontalWritingMode())
1530         return child->isRenderBlockFlow() ? toRenderBlockFlow(child)->mustDiscardMarginAfter() : (child->style()->marginAfterCollapse() == MDISCARD);
1531
1532     // FIXME: We return false here because the implementation is not geometrically complete. We have values only for before/after, not start/end.
1533     // In case the boxes are perpendicular we assume the property is not specified.
1534     return false;
1535 }
1536
1537 bool RenderBlockFlow::mustDiscardMarginAfterForChild(const RenderBox* child) const
1538 {
1539     ASSERT(!child->selfNeedsLayout());
1540     if (!child->isWritingModeRoot())
1541         return child->isRenderBlockFlow() ? toRenderBlockFlow(child)->mustDiscardMarginAfter() : (child->style()->marginAfterCollapse() == MDISCARD);
1542     if (child->isHorizontalWritingMode() == isHorizontalWritingMode())
1543         return child->isRenderBlockFlow() ? toRenderBlockFlow(child)->mustDiscardMarginBefore() : (child->style()->marginBeforeCollapse() == MDISCARD);
1544
1545     // FIXME: See |mustDiscardMarginBeforeForChild| above.
1546     return false;
1547 }
1548
1549 void RenderBlockFlow::setMaxMarginBeforeValues(LayoutUnit pos, LayoutUnit neg)
1550 {
1551     if (!m_rareData) {
1552         if (pos == RenderBlockFlowRareData::positiveMarginBeforeDefault(this) && neg == RenderBlockFlowRareData::negativeMarginBeforeDefault(this))
1553             return;
1554         m_rareData = adoptPtr(new RenderBlockFlowRareData(this));
1555     }
1556     m_rareData->m_margins.setPositiveMarginBefore(pos);
1557     m_rareData->m_margins.setNegativeMarginBefore(neg);
1558 }
1559
1560 void RenderBlockFlow::setMaxMarginAfterValues(LayoutUnit pos, LayoutUnit neg)
1561 {
1562     if (!m_rareData) {
1563         if (pos == RenderBlockFlowRareData::positiveMarginAfterDefault(this) && neg == RenderBlockFlowRareData::negativeMarginAfterDefault(this))
1564             return;
1565         m_rareData = adoptPtr(new RenderBlockFlowRareData(this));
1566     }
1567     m_rareData->m_margins.setPositiveMarginAfter(pos);
1568     m_rareData->m_margins.setNegativeMarginAfter(neg);
1569 }
1570
1571 bool RenderBlockFlow::mustSeparateMarginBeforeForChild(const RenderBox* child) const
1572 {
1573     ASSERT(!child->selfNeedsLayout());
1574     const RenderStyle* childStyle = child->style();
1575     if (!child->isWritingModeRoot())
1576         return childStyle->marginBeforeCollapse() == MSEPARATE;
1577     if (child->isHorizontalWritingMode() == isHorizontalWritingMode())
1578         return childStyle->marginAfterCollapse() == MSEPARATE;
1579
1580     // FIXME: See |mustDiscardMarginBeforeForChild| above.
1581     return false;
1582 }
1583
1584 bool RenderBlockFlow::mustSeparateMarginAfterForChild(const RenderBox* child) const
1585 {
1586     ASSERT(!child->selfNeedsLayout());
1587     const RenderStyle* childStyle = child->style();
1588     if (!child->isWritingModeRoot())
1589         return childStyle->marginAfterCollapse() == MSEPARATE;
1590     if (child->isHorizontalWritingMode() == isHorizontalWritingMode())
1591         return childStyle->marginBeforeCollapse() == MSEPARATE;
1592
1593     // FIXME: See |mustDiscardMarginBeforeForChild| above.
1594     return false;
1595 }
1596
1597 LayoutUnit RenderBlockFlow::applyBeforeBreak(RenderBox* child, LayoutUnit logicalOffset)
1598 {
1599     // FIXME: Add page break checking here when we support printing.
1600     RenderFlowThread* flowThread = flowThreadContainingBlock();
1601     bool isInsideMulticolFlowThread = flowThread;
1602     bool checkColumnBreaks = isInsideMulticolFlowThread || view()->layoutState()->isPaginatingColumns();
1603     bool checkPageBreaks = !checkColumnBreaks && view()->layoutState()->pageLogicalHeight(); // FIXME: Once columns can print we have to check this.
1604     bool checkBeforeAlways = (checkColumnBreaks && child->style()->columnBreakBefore() == PBALWAYS)
1605         || (checkPageBreaks && child->style()->pageBreakBefore() == PBALWAYS);
1606     if (checkBeforeAlways && inNormalFlow(child)) {
1607         if (checkColumnBreaks) {
1608             if (isInsideMulticolFlowThread) {
1609                 LayoutUnit offsetBreakAdjustment = 0;
1610                 if (flowThread->addForcedRegionBreak(offsetFromLogicalTopOfFirstPage() + logicalOffset, child, true, &offsetBreakAdjustment))
1611                     return logicalOffset + offsetBreakAdjustment;
1612             } else {
1613                 view()->layoutState()->addForcedColumnBreak(*child, logicalOffset);
1614             }
1615         }
1616         return nextPageLogicalTop(logicalOffset, IncludePageBoundary);
1617     }
1618     return logicalOffset;
1619 }
1620
1621 LayoutUnit RenderBlockFlow::applyAfterBreak(RenderBox* child, LayoutUnit logicalOffset, MarginInfo& marginInfo)
1622 {
1623     // FIXME: Add page break checking here when we support printing.
1624     RenderFlowThread* flowThread = flowThreadContainingBlock();
1625     bool isInsideMulticolFlowThread = flowThread;
1626     bool checkColumnBreaks = isInsideMulticolFlowThread || view()->layoutState()->isPaginatingColumns();
1627     bool checkPageBreaks = !checkColumnBreaks && view()->layoutState()->pageLogicalHeight(); // FIXME: Once columns can print we have to check this.
1628     bool checkAfterAlways = (checkColumnBreaks && child->style()->columnBreakAfter() == PBALWAYS)
1629         || (checkPageBreaks && child->style()->pageBreakAfter() == PBALWAYS);
1630     if (checkAfterAlways && inNormalFlow(child)) {
1631         LayoutUnit marginOffset = marginInfo.canCollapseWithMarginBefore() ? LayoutUnit() : marginInfo.margin();
1632
1633         // So our margin doesn't participate in the next collapsing steps.
1634         marginInfo.clearMargin();
1635
1636         if (checkColumnBreaks) {
1637             if (isInsideMulticolFlowThread) {
1638                 LayoutUnit offsetBreakAdjustment = 0;
1639                 if (flowThread->addForcedRegionBreak(offsetFromLogicalTopOfFirstPage() + logicalOffset + marginOffset, child, false, &offsetBreakAdjustment))
1640                     return logicalOffset + marginOffset + offsetBreakAdjustment;
1641             } else {
1642                 view()->layoutState()->addForcedColumnBreak(*child, logicalOffset);
1643             }
1644         }
1645         return nextPageLogicalTop(logicalOffset, IncludePageBoundary);
1646     }
1647     return logicalOffset;
1648 }
1649
1650 void RenderBlockFlow::addOverflowFromFloats()
1651 {
1652     if (!m_floatingObjects)
1653         return;
1654
1655     const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
1656     FloatingObjectSetIterator end = floatingObjectSet.end();
1657     for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
1658         FloatingObject* floatingObject = it->get();
1659         if (floatingObject->isDescendant())
1660             addOverflowFromChild(floatingObject->renderer(), IntSize(xPositionForFloatIncludingMargin(floatingObject), yPositionForFloatIncludingMargin(floatingObject)));
1661     }
1662 }
1663
1664 void RenderBlockFlow::computeOverflow(LayoutUnit oldClientAfterEdge, bool recomputeFloats)
1665 {
1666     RenderBlock::computeOverflow(oldClientAfterEdge, recomputeFloats);
1667     if (!hasColumns() && (recomputeFloats || createsBlockFormattingContext() || hasSelfPaintingLayer()))
1668         addOverflowFromFloats();
1669 }
1670
1671 RootInlineBox* RenderBlockFlow::createAndAppendRootInlineBox()
1672 {
1673     RootInlineBox* rootBox = createRootInlineBox();
1674     m_lineBoxes.appendLineBox(rootBox);
1675
1676     if (UNLIKELY(AXObjectCache::accessibilityEnabled()) && m_lineBoxes.firstLineBox() == rootBox) {
1677         if (AXObjectCache* cache = document().existingAXObjectCache())
1678             cache->recomputeIsIgnored(this);
1679     }
1680
1681     return rootBox;
1682 }
1683
1684 void RenderBlockFlow::deleteLineBoxTree()
1685 {
1686     if (containsFloats())
1687         m_floatingObjects->clearLineBoxTreePointers();
1688     RenderBlock::deleteLineBoxTree();
1689 }
1690
1691 void RenderBlockFlow::markAllDescendantsWithFloatsForLayout(RenderBox* floatToRemove, bool inLayout)
1692 {
1693     if (!everHadLayout() && !containsFloats())
1694         return;
1695
1696     MarkingBehavior markParents = inLayout ? MarkOnlyThis : MarkContainingBlockChain;
1697     setChildNeedsLayout(markParents);
1698
1699     if (floatToRemove)
1700         removeFloatingObject(floatToRemove);
1701
1702     // Iterate over our children and mark them as needed.
1703     if (!childrenInline()) {
1704         for (RenderObject* child = firstChild(); child; child = child->nextSibling()) {
1705             if ((!floatToRemove && child->isFloatingOrOutOfFlowPositioned()) || !child->isRenderBlock())
1706                 continue;
1707             if (!child->isRenderBlockFlow()) {
1708                 RenderBlock* childBlock = toRenderBlock(child);
1709                 if (childBlock->shrinkToAvoidFloats() && childBlock->everHadLayout())
1710                     childBlock->setChildNeedsLayout(markParents);
1711                 continue;
1712             }
1713             RenderBlockFlow* childBlockFlow = toRenderBlockFlow(child);
1714             if ((floatToRemove ? childBlockFlow->containsFloat(floatToRemove) : childBlockFlow->containsFloats()) || childBlockFlow->shrinkToAvoidFloats())
1715                 childBlockFlow->markAllDescendantsWithFloatsForLayout(floatToRemove, inLayout);
1716         }
1717     }
1718 }
1719
1720 void RenderBlockFlow::markSiblingsWithFloatsForLayout(RenderBox* floatToRemove)
1721 {
1722     if (!m_floatingObjects)
1723         return;
1724
1725     const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
1726     FloatingObjectSetIterator end = floatingObjectSet.end();
1727
1728     for (RenderObject* next = nextSibling(); next; next = next->nextSibling()) {
1729         if (!next->isRenderBlockFlow() || next->isFloatingOrOutOfFlowPositioned() || toRenderBlock(next)->avoidsFloats())
1730             continue;
1731
1732         RenderBlockFlow* nextBlock = toRenderBlockFlow(next);
1733         for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
1734             RenderBox* floatingBox = (*it)->renderer();
1735             if (floatToRemove && floatingBox != floatToRemove)
1736                 continue;
1737             if (nextBlock->containsFloat(floatingBox))
1738                 nextBlock->markAllDescendantsWithFloatsForLayout(floatingBox);
1739         }
1740     }
1741 }
1742
1743 LayoutUnit RenderBlockFlow::getClearDelta(RenderBox* child, LayoutUnit logicalTop)
1744 {
1745     // There is no need to compute clearance if we have no floats.
1746     if (!containsFloats())
1747         return 0;
1748
1749     // At least one float is present. We need to perform the clearance computation.
1750     bool clearSet = child->style()->clear() != CNONE;
1751     LayoutUnit logicalBottom = 0;
1752     switch (child->style()->clear()) {
1753     case CNONE:
1754         break;
1755     case CLEFT:
1756         logicalBottom = lowestFloatLogicalBottom(FloatingObject::FloatLeft);
1757         break;
1758     case CRIGHT:
1759         logicalBottom = lowestFloatLogicalBottom(FloatingObject::FloatRight);
1760         break;
1761     case CBOTH:
1762         logicalBottom = lowestFloatLogicalBottom();
1763         break;
1764     }
1765
1766     // We also clear floats if we are too big to sit on the same line as a float (and wish to avoid floats by default).
1767     LayoutUnit result = clearSet ? max<LayoutUnit>(0, logicalBottom - logicalTop) : LayoutUnit();
1768     if (!result && child->avoidsFloats()) {
1769         LayoutUnit newLogicalTop = logicalTop;
1770         while (true) {
1771             LayoutUnit availableLogicalWidthAtNewLogicalTopOffset = availableLogicalWidthForLine(newLogicalTop, false, logicalHeightForChild(child));
1772             if (availableLogicalWidthAtNewLogicalTopOffset == availableLogicalWidthForContent())
1773                 return newLogicalTop - logicalTop;
1774
1775             LayoutRect borderBox = child->borderBoxRect();
1776             LayoutUnit childLogicalWidthAtOldLogicalTopOffset = isHorizontalWritingMode() ? borderBox.width() : borderBox.height();
1777
1778             // FIXME: None of this is right for perpendicular writing-mode children.
1779             LayoutUnit childOldLogicalWidth = child->logicalWidth();
1780             LayoutUnit childOldMarginLeft = child->marginLeft();
1781             LayoutUnit childOldMarginRight = child->marginRight();
1782             LayoutUnit childOldLogicalTop = child->logicalTop();
1783
1784             child->setLogicalTop(newLogicalTop);
1785             child->updateLogicalWidth();
1786             borderBox = child->borderBoxRect();
1787             LayoutUnit childLogicalWidthAtNewLogicalTopOffset = isHorizontalWritingMode() ? borderBox.width() : borderBox.height();
1788
1789             child->setLogicalTop(childOldLogicalTop);
1790             child->setLogicalWidth(childOldLogicalWidth);
1791             child->setMarginLeft(childOldMarginLeft);
1792             child->setMarginRight(childOldMarginRight);
1793
1794             if (childLogicalWidthAtNewLogicalTopOffset <= availableLogicalWidthAtNewLogicalTopOffset) {
1795                 // Even though we may not be moving, if the logical width did shrink because of the presence of new floats, then
1796                 // we need to force a relayout as though we shifted. This happens because of the dynamic addition of overhanging floats
1797                 // from previous siblings when negative margins exist on a child (see the addOverhangingFloats call at the end of collapseMargins).
1798                 if (childLogicalWidthAtOldLogicalTopOffset != childLogicalWidthAtNewLogicalTopOffset)
1799                     child->setChildNeedsLayout(MarkOnlyThis);
1800                 return newLogicalTop - logicalTop;
1801             }
1802
1803             newLogicalTop = nextFloatLogicalBottomBelow(newLogicalTop);
1804             ASSERT(newLogicalTop >= logicalTop);
1805             if (newLogicalTop < logicalTop)
1806                 break;
1807         }
1808         ASSERT_NOT_REACHED();
1809     }
1810     return result;
1811 }
1812
1813 void RenderBlockFlow::createFloatingObjects()
1814 {
1815     m_floatingObjects = adoptPtr(new FloatingObjects(this, isHorizontalWritingMode()));
1816 }
1817
1818 void RenderBlockFlow::styleWillChange(StyleDifference diff, const RenderStyle& newStyle)
1819 {
1820     RenderStyle* oldStyle = style();
1821     s_canPropagateFloatIntoSibling = oldStyle ? !isFloatingOrOutOfFlowPositioned() && !avoidsFloats() : false;
1822     if (oldStyle && parent() && diff.needsFullLayout() && oldStyle->position() != newStyle.position()
1823         && containsFloats() && !isFloating() && !isOutOfFlowPositioned() && newStyle.hasOutOfFlowPosition())
1824             markAllDescendantsWithFloatsForLayout();
1825
1826     RenderBlock::styleWillChange(diff, newStyle);
1827 }
1828
1829 void RenderBlockFlow::styleDidChange(StyleDifference diff, const RenderStyle* oldStyle)
1830 {
1831     RenderBlock::styleDidChange(diff, oldStyle);
1832
1833     // After our style changed, if we lose our ability to propagate floats into next sibling
1834     // blocks, then we need to find the top most parent containing that overhanging float and
1835     // then mark its descendants with floats for layout and clear all floats from its next
1836     // sibling blocks that exist in our floating objects list. See bug 56299 and 62875.
1837     bool canPropagateFloatIntoSibling = !isFloatingOrOutOfFlowPositioned() && !avoidsFloats();
1838     if (diff.needsFullLayout() && s_canPropagateFloatIntoSibling && !canPropagateFloatIntoSibling && hasOverhangingFloats()) {
1839         RenderBlockFlow* parentBlockFlow = this;
1840         const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
1841         FloatingObjectSetIterator end = floatingObjectSet.end();
1842
1843         for (RenderObject* curr = parent(); curr && !curr->isRenderView(); curr = curr->parent()) {
1844             if (curr->isRenderBlockFlow()) {
1845                 RenderBlockFlow* currBlock = toRenderBlockFlow(curr);
1846
1847                 if (currBlock->hasOverhangingFloats()) {
1848                     for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
1849                         RenderBox* renderer = (*it)->renderer();
1850                         if (currBlock->hasOverhangingFloat(renderer)) {
1851                             parentBlockFlow = currBlock;
1852                             break;
1853                         }
1854                     }
1855                 }
1856             }
1857         }
1858
1859         parentBlockFlow->markAllDescendantsWithFloatsForLayout();
1860         parentBlockFlow->markSiblingsWithFloatsForLayout();
1861     }
1862
1863     if (diff.needsFullLayout() || !oldStyle)
1864         createOrDestroyMultiColumnFlowThreadIfNeeded();
1865 }
1866
1867 void RenderBlockFlow::updateStaticInlinePositionForChild(RenderBox* child, LayoutUnit logicalTop)
1868 {
1869     if (child->style()->isOriginalDisplayInlineType())
1870         setStaticInlinePositionForChild(child, logicalTop, startAlignedOffsetForLine(logicalTop, false));
1871     else
1872         setStaticInlinePositionForChild(child, logicalTop, startOffsetForContent());
1873 }
1874
1875 void RenderBlockFlow::setStaticInlinePositionForChild(RenderBox* child, LayoutUnit blockOffset, LayoutUnit inlinePosition)
1876 {
1877     child->layer()->setStaticInlinePosition(inlinePosition);
1878 }
1879
1880 void RenderBlockFlow::addChild(RenderObject* newChild, RenderObject* beforeChild)
1881 {
1882     if (RenderMultiColumnFlowThread* flowThread = multiColumnFlowThread()) {
1883         flowThread->addChild(newChild, beforeChild);
1884         return;
1885     }
1886     RenderBlock::addChild(newChild, beforeChild);
1887 }
1888
1889 void RenderBlockFlow::moveAllChildrenIncludingFloatsTo(RenderBlock* toBlock, bool fullRemoveInsert)
1890 {
1891     RenderBlockFlow* toBlockFlow = toRenderBlockFlow(toBlock);
1892     moveAllChildrenTo(toBlockFlow, fullRemoveInsert);
1893
1894     // When a portion of the render tree is being detached, anonymous blocks
1895     // will be combined as their children are deleted. In this process, the
1896     // anonymous block later in the tree is merged into the one preceeding it.
1897     // It can happen that the later block (this) contains floats that the
1898     // previous block (toBlockFlow) did not contain, and thus are not in the
1899     // floating objects list for toBlockFlow. This can result in toBlockFlow containing
1900     // floats that are not in it's floating objects list, but are in the
1901     // floating objects lists of siblings and parents. This can cause problems
1902     // when the float itself is deleted, since the deletion code assumes that
1903     // if a float is not in it's containing block's floating objects list, it
1904     // isn't in any floating objects list. In order to preserve this condition
1905     // (removing it has serious performance implications), we need to copy the
1906     // floating objects from the old block (this) to the new block (toBlockFlow).
1907     // The float's metrics will likely all be wrong, but since toBlockFlow is
1908     // already marked for layout, this will get fixed before anything gets
1909     // displayed.
1910     // See bug https://code.google.com/p/chromium/issues/detail?id=230907
1911     if (m_floatingObjects) {
1912         if (!toBlockFlow->m_floatingObjects)
1913             toBlockFlow->createFloatingObjects();
1914
1915         const FloatingObjectSet& fromFloatingObjectSet = m_floatingObjects->set();
1916         FloatingObjectSetIterator end = fromFloatingObjectSet.end();
1917
1918         for (FloatingObjectSetIterator it = fromFloatingObjectSet.begin(); it != end; ++it) {
1919             FloatingObject* floatingObject = it->get();
1920
1921             // Don't insert the object again if it's already in the list
1922             if (toBlockFlow->containsFloat(floatingObject->renderer()))
1923                 continue;
1924
1925             toBlockFlow->m_floatingObjects->add(floatingObject->unsafeClone());
1926         }
1927     }
1928
1929 }
1930
1931 void RenderBlockFlow::repaintOverhangingFloats(bool paintAllDescendants)
1932 {
1933     // Repaint any overhanging floats (if we know we're the one to paint them).
1934     // Otherwise, bail out.
1935     if (!hasOverhangingFloats())
1936         return;
1937
1938     // FIXME: Avoid disabling LayoutState. At the very least, don't disable it for floats originating
1939     // in this block. Better yet would be to push extra state for the containers of other floats.
1940     ForceHorriblySlowRectMapping slowRectMapping(*this);
1941     const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
1942     FloatingObjectSetIterator end = floatingObjectSet.end();
1943     for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
1944         FloatingObject* floatingObject = it->get();
1945         // Only repaint the object if it is overhanging, is not in its own layer, and
1946         // is our responsibility to paint (m_shouldPaint is set). When paintAllDescendants is true, the latter
1947         // condition is replaced with being a descendant of us.
1948         if (logicalBottomForFloat(floatingObject) > logicalHeight()
1949             && !floatingObject->renderer()->hasSelfPaintingLayer()
1950             && (floatingObject->shouldPaint() || (paintAllDescendants && floatingObject->renderer()->isDescendantOf(this)))) {
1951
1952             RenderBox* floatingRenderer = floatingObject->renderer();
1953             if (RuntimeEnabledFeatures::repaintAfterLayoutEnabled())
1954                 floatingRenderer->setShouldDoFullPaintInvalidationAfterLayout(true);
1955             else
1956                 floatingRenderer->paintInvalidationForWholeRenderer();
1957
1958             floatingRenderer->repaintOverhangingFloats(false);
1959         }
1960     }
1961 }
1962
1963 void RenderBlockFlow::invalidatePaintForOverflow()
1964 {
1965     // FIXME: We could tighten up the left and right invalidation points if we let layoutInlineChildren fill them in based off the particular lines
1966     // it had to lay out. We wouldn't need the hasOverflowClip() hack in that case either.
1967     LayoutUnit repaintLogicalLeft = logicalLeftVisualOverflow();
1968     LayoutUnit repaintLogicalRight = logicalRightVisualOverflow();
1969     if (hasOverflowClip()) {
1970         // If we have clipped overflow, we should use layout overflow as well, since visual overflow from lines didn't propagate to our block's overflow.
1971         // Note the old code did this as well but even for overflow:visible. The addition of hasOverflowClip() at least tightens up the hack a bit.
1972         // layoutInlineChildren should be patched to compute the entire repaint rect.
1973         repaintLogicalLeft = min(repaintLogicalLeft, logicalLeftLayoutOverflow());
1974         repaintLogicalRight = max(repaintLogicalRight, logicalRightLayoutOverflow());
1975     }
1976
1977     LayoutRect repaintRect;
1978     if (isHorizontalWritingMode())
1979         repaintRect = LayoutRect(repaintLogicalLeft, m_repaintLogicalTop, repaintLogicalRight - repaintLogicalLeft, m_repaintLogicalBottom - m_repaintLogicalTop);
1980     else
1981         repaintRect = LayoutRect(m_repaintLogicalTop, repaintLogicalLeft, m_repaintLogicalBottom - m_repaintLogicalTop, repaintLogicalRight - repaintLogicalLeft);
1982
1983     // The repaint rect may be split across columns, in which case adjustRectForColumns() will return the union.
1984     adjustRectForColumns(repaintRect);
1985
1986     if (hasOverflowClip()) {
1987         // Adjust repaint rect for scroll offset
1988         repaintRect.move(-scrolledContentOffset());
1989
1990         // Don't allow this rect to spill out of our overflow box.
1991         repaintRect.intersect(LayoutRect(LayoutPoint(), size()));
1992     }
1993
1994     // Make sure the rect is still non-empty after intersecting for overflow above
1995     if (!repaintRect.isEmpty()) {
1996         // Hits in media/event-attributes.html
1997         DisableCompositingQueryAsserts disabler;
1998
1999         invalidatePaintRectangle(repaintRect); // We need to do a partial repaint of our content.
2000         if (hasReflection())
2001             invalidatePaintRectangle(reflectedRect(repaintRect));
2002     }
2003
2004     m_repaintLogicalTop = 0;
2005     m_repaintLogicalBottom = 0;
2006 }
2007
2008 void RenderBlockFlow::paintFloats(PaintInfo& paintInfo, const LayoutPoint& paintOffset, bool preservePhase)
2009 {
2010     if (!m_floatingObjects)
2011         return;
2012
2013     const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
2014     FloatingObjectSetIterator end = floatingObjectSet.end();
2015     for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
2016         FloatingObject* floatingObject = it->get();
2017         // Only paint the object if our m_shouldPaint flag is set.
2018         if (floatingObject->shouldPaint() && !floatingObject->renderer()->hasSelfPaintingLayer()) {
2019             PaintInfo currentPaintInfo(paintInfo);
2020             currentPaintInfo.phase = preservePhase ? paintInfo.phase : PaintPhaseBlockBackground;
2021             // FIXME: LayoutPoint version of xPositionForFloatIncludingMargin would make this much cleaner.
2022             LayoutPoint childPoint = flipFloatForWritingModeForChild(floatingObject, LayoutPoint(paintOffset.x() + xPositionForFloatIncludingMargin(floatingObject) - floatingObject->renderer()->x(), paintOffset.y() + yPositionForFloatIncludingMargin(floatingObject) - floatingObject->renderer()->y()));
2023             floatingObject->renderer()->paint(currentPaintInfo, childPoint);
2024             if (!preservePhase) {
2025                 currentPaintInfo.phase = PaintPhaseChildBlockBackgrounds;
2026                 floatingObject->renderer()->paint(currentPaintInfo, childPoint);
2027                 currentPaintInfo.phase = PaintPhaseFloat;
2028                 floatingObject->renderer()->paint(currentPaintInfo, childPoint);
2029                 currentPaintInfo.phase = PaintPhaseForeground;
2030                 floatingObject->renderer()->paint(currentPaintInfo, childPoint);
2031                 currentPaintInfo.phase = PaintPhaseOutline;
2032                 floatingObject->renderer()->paint(currentPaintInfo, childPoint);
2033             }
2034         }
2035     }
2036 }
2037
2038 void RenderBlockFlow::clipOutFloatingObjects(RenderBlock* rootBlock, const PaintInfo* paintInfo, const LayoutPoint& rootBlockPhysicalPosition, const LayoutSize& offsetFromRootBlock)
2039 {
2040     if (m_floatingObjects) {
2041         const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
2042         FloatingObjectSetIterator end = floatingObjectSet.end();
2043         for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
2044             FloatingObject* floatingObject = it->get();
2045             LayoutRect floatBox(offsetFromRootBlock.width() + xPositionForFloatIncludingMargin(floatingObject),
2046                 offsetFromRootBlock.height() + yPositionForFloatIncludingMargin(floatingObject),
2047                 floatingObject->renderer()->width(), floatingObject->renderer()->height());
2048             rootBlock->flipForWritingMode(floatBox);
2049             floatBox.move(rootBlockPhysicalPosition.x(), rootBlockPhysicalPosition.y());
2050             paintInfo->context->clipOut(pixelSnappedIntRect(floatBox));
2051         }
2052     }
2053 }
2054
2055 void RenderBlockFlow::clearFloats(EClear clear)
2056 {
2057     positionNewFloats();
2058     // set y position
2059     LayoutUnit newY = 0;
2060     switch (clear) {
2061     case CLEFT:
2062         newY = lowestFloatLogicalBottom(FloatingObject::FloatLeft);
2063         break;
2064     case CRIGHT:
2065         newY = lowestFloatLogicalBottom(FloatingObject::FloatRight);
2066         break;
2067     case CBOTH:
2068         newY = lowestFloatLogicalBottom();
2069     default:
2070         break;
2071     }
2072     if (height() < newY)
2073         setLogicalHeight(newY);
2074 }
2075
2076 bool RenderBlockFlow::containsFloat(RenderBox* renderer) const
2077 {
2078     return m_floatingObjects && m_floatingObjects->set().contains<FloatingObjectHashTranslator>(renderer);
2079 }
2080
2081 void RenderBlockFlow::removeFloatingObjects()
2082 {
2083     if (!m_floatingObjects)
2084         return;
2085
2086     markSiblingsWithFloatsForLayout();
2087
2088     m_floatingObjects->clear();
2089 }
2090
2091 LayoutPoint RenderBlockFlow::flipFloatForWritingModeForChild(const FloatingObject* child, const LayoutPoint& point) const
2092 {
2093     if (!style()->isFlippedBlocksWritingMode())
2094         return point;
2095
2096     // This is similar to RenderBox::flipForWritingModeForChild. We have to subtract out our left/top offsets twice, since
2097     // it's going to get added back in. We hide this complication here so that the calling code looks normal for the unflipped
2098     // case.
2099     if (isHorizontalWritingMode())
2100         return LayoutPoint(point.x(), point.y() + height() - child->renderer()->height() - 2 * yPositionForFloatIncludingMargin(child));
2101     return LayoutPoint(point.x() + width() - child->renderer()->width() - 2 * xPositionForFloatIncludingMargin(child), point.y());
2102 }
2103
2104 LayoutUnit RenderBlockFlow::logicalLeftOffsetForPositioningFloat(LayoutUnit logicalTop, LayoutUnit fixedOffset, bool applyTextIndent, LayoutUnit* heightRemaining) const
2105 {
2106     LayoutUnit offset = fixedOffset;
2107     if (m_floatingObjects && m_floatingObjects->hasLeftObjects())
2108         offset = m_floatingObjects->logicalLeftOffsetForPositioningFloat(fixedOffset, logicalTop, heightRemaining);
2109     return adjustLogicalLeftOffsetForLine(offset, applyTextIndent);
2110 }
2111
2112 LayoutUnit RenderBlockFlow::logicalRightOffsetForPositioningFloat(LayoutUnit logicalTop, LayoutUnit fixedOffset, bool applyTextIndent, LayoutUnit* heightRemaining) const
2113 {
2114     LayoutUnit offset = fixedOffset;
2115     if (m_floatingObjects && m_floatingObjects->hasRightObjects())
2116         offset = m_floatingObjects->logicalRightOffsetForPositioningFloat(fixedOffset, logicalTop, heightRemaining);
2117     return adjustLogicalRightOffsetForLine(offset, applyTextIndent);
2118 }
2119
2120 LayoutUnit RenderBlockFlow::adjustLogicalLeftOffsetForLine(LayoutUnit offsetFromFloats, bool applyTextIndent) const
2121 {
2122     LayoutUnit left = offsetFromFloats;
2123
2124     if (applyTextIndent && style()->isLeftToRightDirection())
2125         left += textIndentOffset();
2126
2127     return left;
2128 }
2129
2130 LayoutUnit RenderBlockFlow::adjustLogicalRightOffsetForLine(LayoutUnit offsetFromFloats, bool applyTextIndent) const
2131 {
2132     LayoutUnit right = offsetFromFloats;
2133
2134     if (applyTextIndent && !style()->isLeftToRightDirection())
2135         right -= textIndentOffset();
2136
2137     return right;
2138 }
2139
2140 LayoutPoint RenderBlockFlow::computeLogicalLocationForFloat(const FloatingObject* floatingObject, LayoutUnit logicalTopOffset) const
2141 {
2142     RenderBox* childBox = floatingObject->renderer();
2143     LayoutUnit logicalLeftOffset = logicalLeftOffsetForContent(); // Constant part of left offset.
2144     LayoutUnit logicalRightOffset; // Constant part of right offset.
2145     logicalRightOffset = logicalRightOffsetForContent();
2146
2147     LayoutUnit floatLogicalWidth = min(logicalWidthForFloat(floatingObject), logicalRightOffset - logicalLeftOffset); // The width we look for.
2148
2149     LayoutUnit floatLogicalLeft;
2150
2151     bool insideFlowThread = flowThreadContainingBlock();
2152
2153     if (childBox->style()->floating() == LeftFloat) {
2154         LayoutUnit heightRemainingLeft = 1;
2155         LayoutUnit heightRemainingRight = 1;
2156         floatLogicalLeft = logicalLeftOffsetForPositioningFloat(logicalTopOffset, logicalLeftOffset, false, &heightRemainingLeft);
2157         while (logicalRightOffsetForPositioningFloat(logicalTopOffset, logicalRightOffset, false, &heightRemainingRight) - floatLogicalLeft < floatLogicalWidth) {
2158             logicalTopOffset += min(heightRemainingLeft, heightRemainingRight);
2159             floatLogicalLeft = logicalLeftOffsetForPositioningFloat(logicalTopOffset, logicalLeftOffset, false, &heightRemainingLeft);
2160             if (insideFlowThread) {
2161                 // Have to re-evaluate all of our offsets, since they may have changed.
2162                 logicalRightOffset = logicalRightOffsetForContent(); // Constant part of right offset.
2163                 logicalLeftOffset = logicalLeftOffsetForContent(); // Constant part of left offset.
2164                 floatLogicalWidth = min(logicalWidthForFloat(floatingObject), logicalRightOffset - logicalLeftOffset);
2165             }
2166         }
2167         floatLogicalLeft = max(logicalLeftOffset - borderAndPaddingLogicalLeft(), floatLogicalLeft);
2168     } else {
2169         LayoutUnit heightRemainingLeft = 1;
2170         LayoutUnit heightRemainingRight = 1;
2171         floatLogicalLeft = logicalRightOffsetForPositioningFloat(logicalTopOffset, logicalRightOffset, false, &heightRemainingRight);
2172         while (floatLogicalLeft - logicalLeftOffsetForPositioningFloat(logicalTopOffset, logicalLeftOffset, false, &heightRemainingLeft) < floatLogicalWidth) {
2173             logicalTopOffset += min(heightRemainingLeft, heightRemainingRight);
2174             floatLogicalLeft = logicalRightOffsetForPositioningFloat(logicalTopOffset, logicalRightOffset, false, &heightRemainingRight);
2175             if (insideFlowThread) {
2176                 // Have to re-evaluate all of our offsets, since they may have changed.
2177                 logicalRightOffset = logicalRightOffsetForContent(); // Constant part of right offset.
2178                 logicalLeftOffset = logicalLeftOffsetForContent(); // Constant part of left offset.
2179                 floatLogicalWidth = min(logicalWidthForFloat(floatingObject), logicalRightOffset - logicalLeftOffset);
2180             }
2181         }
2182         // Use the original width of the float here, since the local variable
2183         // |floatLogicalWidth| was capped to the available line width. See
2184         // fast/block/float/clamped-right-float.html.
2185         floatLogicalLeft -= logicalWidthForFloat(floatingObject);
2186     }
2187
2188     return LayoutPoint(floatLogicalLeft, logicalTopOffset);
2189 }
2190
2191 FloatingObject* RenderBlockFlow::insertFloatingObject(RenderBox* floatBox)
2192 {
2193     ASSERT(floatBox->isFloating());
2194
2195     // Create the list of special objects if we don't aleady have one
2196     if (!m_floatingObjects) {
2197         createFloatingObjects();
2198     } else {
2199         // Don't insert the object again if it's already in the list
2200         const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
2201         FloatingObjectSetIterator it = floatingObjectSet.find<FloatingObjectHashTranslator>(floatBox);
2202         if (it != floatingObjectSet.end())
2203             return it->get();
2204     }
2205
2206     // Create the special object entry & append it to the list
2207
2208     OwnPtr<FloatingObject> newObj = FloatingObject::create(floatBox);
2209
2210     // Our location is irrelevant if we're unsplittable or no pagination is in effect.
2211     // Just go ahead and lay out the float.
2212     bool isChildRenderBlock = floatBox->isRenderBlock();
2213     if (isChildRenderBlock && !floatBox->needsLayout() && view()->layoutState()->pageLogicalHeightChanged())
2214         floatBox->setChildNeedsLayout(MarkOnlyThis);
2215
2216     bool needsBlockDirectionLocationSetBeforeLayout = isChildRenderBlock && view()->layoutState()->needsBlockDirectionLocationSetBeforeLayout();
2217     if (!needsBlockDirectionLocationSetBeforeLayout || isWritingModeRoot()) { // We are unsplittable if we're a block flow root.
2218         floatBox->layoutIfNeeded();
2219     } else {
2220         floatBox->updateLogicalWidth();
2221         floatBox->computeAndSetBlockDirectionMargins(this);
2222     }
2223
2224     setLogicalWidthForFloat(newObj.get(), logicalWidthForChild(floatBox) + marginStartForChild(floatBox) + marginEndForChild(floatBox));
2225
2226     return m_floatingObjects->add(newObj.release());
2227 }
2228
2229 void RenderBlockFlow::removeFloatingObject(RenderBox* floatBox)
2230 {
2231     if (m_floatingObjects) {
2232         const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
2233         FloatingObjectSetIterator it = floatingObjectSet.find<FloatingObjectHashTranslator>(floatBox);
2234         if (it != floatingObjectSet.end()) {
2235             FloatingObject* floatingObject = it->get();
2236             if (childrenInline()) {
2237                 LayoutUnit logicalTop = logicalTopForFloat(floatingObject);
2238                 LayoutUnit logicalBottom = logicalBottomForFloat(floatingObject);
2239
2240                 // Fix for https://bugs.webkit.org/show_bug.cgi?id=54995.
2241                 if (logicalBottom < 0 || logicalBottom < logicalTop || logicalTop == LayoutUnit::max()) {
2242                     logicalBottom = LayoutUnit::max();
2243                 } else {
2244                     // Special-case zero- and less-than-zero-height floats: those don't touch
2245                     // the line that they're on, but it still needs to be dirtied. This is
2246                     // accomplished by pretending they have a height of 1.
2247                     logicalBottom = max(logicalBottom, logicalTop + 1);
2248                 }
2249                 if (floatingObject->originatingLine()) {
2250                     if (!selfNeedsLayout()) {
2251                         ASSERT(floatingObject->originatingLine()->renderer() == this);
2252                         floatingObject->originatingLine()->markDirty();
2253                     }
2254 #if ASSERT_ENABLED
2255                     floatingObject->setOriginatingLine(0);
2256 #endif
2257                 }
2258                 markLinesDirtyInBlockRange(0, logicalBottom);
2259             }
2260             m_floatingObjects->remove(floatingObject);
2261         }
2262     }
2263 }
2264
2265 void RenderBlockFlow::removeFloatingObjectsBelow(FloatingObject* lastFloat, int logicalOffset)
2266 {
2267     if (!containsFloats())
2268         return;
2269
2270     const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
2271     FloatingObject* curr = floatingObjectSet.last().get();
2272     while (curr != lastFloat && (!curr->isPlaced() || logicalTopForFloat(curr) >= logicalOffset)) {
2273         m_floatingObjects->remove(curr);
2274         if (floatingObjectSet.isEmpty())
2275             break;
2276         curr = floatingObjectSet.last().get();
2277     }
2278 }
2279
2280 bool RenderBlockFlow::positionNewFloats()
2281 {
2282     if (!m_floatingObjects)
2283         return false;
2284
2285     const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
2286     if (floatingObjectSet.isEmpty())
2287         return false;
2288
2289     // If all floats have already been positioned, then we have no work to do.
2290     if (floatingObjectSet.last()->isPlaced())
2291         return false;
2292
2293     // Move backwards through our floating object list until we find a float that has
2294     // already been positioned. Then we'll be able to move forward, positioning all of
2295     // the new floats that need it.
2296     FloatingObjectSetIterator it = floatingObjectSet.end();
2297     --it; // Go to last item.
2298     FloatingObjectSetIterator begin = floatingObjectSet.begin();
2299     FloatingObject* lastPlacedFloatingObject = 0;
2300     while (it != begin) {
2301         --it;
2302         if ((*it)->isPlaced()) {
2303             lastPlacedFloatingObject = it->get();
2304             ++it;
2305             break;
2306         }
2307     }
2308
2309     LayoutUnit logicalTop = logicalHeight();
2310
2311     // The float cannot start above the top position of the last positioned float.
2312     if (lastPlacedFloatingObject)
2313         logicalTop = max(logicalTopForFloat(lastPlacedFloatingObject), logicalTop);
2314
2315     FloatingObjectSetIterator end = floatingObjectSet.end();
2316     // Now walk through the set of unpositioned floats and place them.
2317     for (; it != end; ++it) {
2318         FloatingObject* floatingObject = it->get();
2319         // The containing block is responsible for positioning floats, so if we have floats in our
2320         // list that come from somewhere else, do not attempt to position them.
2321         if (floatingObject->renderer()->containingBlock() != this)
2322             continue;
2323
2324         RenderBox* childBox = floatingObject->renderer();
2325
2326         // FIXME Investigate if this can be removed. crbug.com/370006
2327         childBox->setMayNeedPaintInvalidation(true);
2328
2329         LayoutUnit childLogicalLeftMargin = style()->isLeftToRightDirection() ? marginStartForChild(childBox) : marginEndForChild(childBox);
2330         LayoutRect oldRect = childBox->frameRect();
2331
2332         if (childBox->style()->clear() & CLEFT)
2333             logicalTop = max(lowestFloatLogicalBottom(FloatingObject::FloatLeft), logicalTop);
2334         if (childBox->style()->clear() & CRIGHT)
2335             logicalTop = max(lowestFloatLogicalBottom(FloatingObject::FloatRight), logicalTop);
2336
2337         LayoutPoint floatLogicalLocation = computeLogicalLocationForFloat(floatingObject, logicalTop);
2338
2339         setLogicalLeftForFloat(floatingObject, floatLogicalLocation.x());
2340
2341         setLogicalLeftForChild(childBox, floatLogicalLocation.x() + childLogicalLeftMargin);
2342         setLogicalTopForChild(childBox, floatLogicalLocation.y() + marginBeforeForChild(childBox));
2343
2344         SubtreeLayoutScope layoutScope(*childBox);
2345         LayoutState* layoutState = view()->layoutState();
2346         bool isPaginated = layoutState->isPaginated();
2347         if (isPaginated && !childBox->needsLayout())
2348             childBox->markForPaginationRelayoutIfNeeded(layoutScope);
2349
2350         childBox->layoutIfNeeded();
2351
2352         if (isPaginated) {
2353             // If we are unsplittable and don't fit, then we need to move down.
2354             // We include our margins as part of the unsplittable area.
2355             LayoutUnit newLogicalTop = adjustForUnsplittableChild(childBox, floatLogicalLocation.y(), true);
2356
2357             // See if we have a pagination strut that is making us move down further.
2358             // Note that an unsplittable child can't also have a pagination strut, so this is
2359             // exclusive with the case above.
2360             RenderBlock* childBlock = childBox->isRenderBlock() ? toRenderBlock(childBox) : 0;
2361             if (childBlock && childBlock->paginationStrut()) {
2362                 newLogicalTop += childBlock->paginationStrut();
2363                 childBlock->setPaginationStrut(0);
2364             }
2365
2366             if (newLogicalTop != floatLogicalLocation.y()) {
2367                 floatingObject->setPaginationStrut(newLogicalTop - floatLogicalLocation.y());
2368
2369                 floatLogicalLocation = computeLogicalLocationForFloat(floatingObject, newLogicalTop);
2370                 setLogicalLeftForFloat(floatingObject, floatLogicalLocation.x());
2371
2372                 setLogicalLeftForChild(childBox, floatLogicalLocation.x() + childLogicalLeftMargin);
2373                 setLogicalTopForChild(childBox, floatLogicalLocation.y() + marginBeforeForChild(childBox));
2374
2375                 if (childBlock)
2376                     childBlock->setChildNeedsLayout(MarkOnlyThis);
2377                 childBox->layoutIfNeeded();
2378             }
2379         }
2380
2381         setLogicalTopForFloat(floatingObject, floatLogicalLocation.y());
2382
2383         setLogicalHeightForFloat(floatingObject, logicalHeightForChild(childBox) + marginBeforeForChild(childBox) + marginAfterForChild(childBox));
2384
2385         m_floatingObjects->addPlacedObject(floatingObject);
2386
2387         if (ShapeOutsideInfo* shapeOutside = childBox->shapeOutsideInfo())
2388             shapeOutside->setReferenceBoxLogicalSize(logicalSizeForChild(childBox));
2389
2390         // If the child moved, we have to repaint it.
2391         if (!RuntimeEnabledFeatures::repaintAfterLayoutEnabled()
2392             && childBox->checkForPaintInvalidationDuringLayout())
2393             childBox->repaintDuringLayoutIfMoved(oldRect);
2394     }
2395     return true;
2396 }
2397
2398 bool RenderBlockFlow::hasOverhangingFloat(RenderBox* renderer)
2399 {
2400     if (!m_floatingObjects || hasColumns() || !parent())
2401         return false;
2402
2403     const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
2404     FloatingObjectSetIterator it = floatingObjectSet.find<FloatingObjectHashTranslator>(renderer);
2405     if (it == floatingObjectSet.end())
2406         return false;
2407
2408     return logicalBottomForFloat(it->get()) > logicalHeight();
2409 }
2410
2411 void RenderBlockFlow::addIntrudingFloats(RenderBlockFlow* prev, LayoutUnit logicalLeftOffset, LayoutUnit logicalTopOffset)
2412 {
2413     ASSERT(!avoidsFloats());
2414
2415     // If we create our own block formatting context then our contents don't interact with floats outside it, even those from our parent.
2416     if (createsBlockFormattingContext())
2417         return;
2418
2419     // If the parent or previous sibling doesn't have any floats to add, don't bother.
2420     if (!prev->m_floatingObjects)
2421         return;
2422
2423     logicalLeftOffset += marginLogicalLeft();
2424
2425     const FloatingObjectSet& prevSet = prev->m_floatingObjects->set();
2426     FloatingObjectSetIterator prevEnd = prevSet.end();
2427     for (FloatingObjectSetIterator prevIt = prevSet.begin(); prevIt != prevEnd; ++prevIt) {
2428         FloatingObject* floatingObject = prevIt->get();
2429         if (logicalBottomForFloat(floatingObject) > logicalTopOffset) {
2430             if (!m_floatingObjects || !m_floatingObjects->set().contains(floatingObject)) {
2431                 // We create the floating object list lazily.
2432                 if (!m_floatingObjects)
2433                     createFloatingObjects();
2434
2435                 // Applying the child's margin makes no sense in the case where the child was passed in.
2436                 // since this margin was added already through the modification of the |logicalLeftOffset| variable
2437                 // above. |logicalLeftOffset| will equal the margin in this case, so it's already been taken
2438                 // into account. Only apply this code if prev is the parent, since otherwise the left margin
2439                 // will get applied twice.
2440                 LayoutSize offset = isHorizontalWritingMode()
2441                     ? LayoutSize(logicalLeftOffset - (prev != parent() ? prev->marginLeft() : LayoutUnit()), logicalTopOffset)
2442                     : LayoutSize(logicalTopOffset, logicalLeftOffset - (prev != parent() ? prev->marginTop() : LayoutUnit()));
2443
2444                 m_floatingObjects->add(floatingObject->copyToNewContainer(offset));
2445             }
2446         }
2447     }
2448 }
2449
2450 void RenderBlockFlow::addOverhangingFloats(RenderBlockFlow* child, bool makeChildPaintOtherFloats)
2451 {
2452     // Prevent floats from being added to the canvas by the root element, e.g., <html>.
2453     if (!child->containsFloats() || child->isRenderRegion() || child->createsBlockFormattingContext())
2454         return;
2455
2456     LayoutUnit childLogicalTop = child->logicalTop();
2457     LayoutUnit childLogicalLeft = child->logicalLeft();
2458
2459     // Floats that will remain the child's responsibility to paint should factor into its
2460     // overflow.
2461     FloatingObjectSetIterator childEnd = child->m_floatingObjects->set().end();
2462     for (FloatingObjectSetIterator childIt = child->m_floatingObjects->set().begin(); childIt != childEnd; ++childIt) {
2463         FloatingObject* floatingObject = childIt->get();
2464         LayoutUnit logicalBottomForFloat = min(this->logicalBottomForFloat(floatingObject), LayoutUnit::max() - childLogicalTop);
2465         LayoutUnit logicalBottom = childLogicalTop + logicalBottomForFloat;
2466
2467         if (logicalBottom > logicalHeight()) {
2468             // If the object is not in the list, we add it now.
2469             if (!containsFloat(floatingObject->renderer())) {
2470                 LayoutSize offset = isHorizontalWritingMode() ? LayoutSize(-childLogicalLeft, -childLogicalTop) : LayoutSize(-childLogicalTop, -childLogicalLeft);
2471                 bool shouldPaint = false;
2472
2473                 // The nearest enclosing layer always paints the float (so that zindex and stacking
2474                 // behaves properly). We always want to propagate the desire to paint the float as
2475                 // far out as we can, to the outermost block that overlaps the float, stopping only
2476                 // if we hit a self-painting layer boundary.
2477                 if (floatingObject->renderer()->enclosingFloatPaintingLayer() == enclosingFloatPaintingLayer()) {
2478                     floatingObject->setShouldPaint(false);
2479                     shouldPaint = true;
2480                 }
2481                 // We create the floating object list lazily.
2482                 if (!m_floatingObjects)
2483                     createFloatingObjects();
2484
2485                 m_floatingObjects->add(floatingObject->copyToNewContainer(offset, shouldPaint, true));
2486             }
2487         } else {
2488             if (makeChildPaintOtherFloats && !floatingObject->shouldPaint() && !floatingObject->renderer()->hasSelfPaintingLayer()
2489                 && floatingObject->renderer()->isDescendantOf(child) && floatingObject->renderer()->enclosingFloatPaintingLayer() == child->enclosingFloatPaintingLayer()) {
2490                 // The float is not overhanging from this block, so if it is a descendant of the child, the child should
2491                 // paint it (the other case is that it is intruding into the child), unless it has its own layer or enclosing
2492                 // layer.
2493                 // If makeChildPaintOtherFloats is false, it means that the child must already know about all the floats
2494                 // it should paint.
2495                 floatingObject->setShouldPaint(true);
2496             }
2497
2498             // Since the float doesn't overhang, it didn't get put into our list. We need to go ahead and add its overflow in to the
2499             // child now.
2500             if (floatingObject->isDescendant())
2501                 child->addOverflowFromChild(floatingObject->renderer(), LayoutSize(xPositionForFloatIncludingMargin(floatingObject), yPositionForFloatIncludingMargin(floatingObject)));
2502         }
2503     }
2504 }
2505
2506 LayoutUnit RenderBlockFlow::lowestFloatLogicalBottom(FloatingObject::Type floatType) const
2507 {
2508     if (!m_floatingObjects)
2509         return 0;
2510
2511     return m_floatingObjects->lowestFloatLogicalBottom(floatType);
2512 }
2513
2514 LayoutUnit RenderBlockFlow::nextFloatLogicalBottomBelow(LayoutUnit logicalHeight, ShapeOutsideFloatOffsetMode offsetMode) const
2515 {
2516     if (!m_floatingObjects)
2517         return logicalHeight;
2518
2519     LayoutUnit logicalBottom;
2520     const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
2521     FloatingObjectSetIterator end = floatingObjectSet.end();
2522     for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
2523         FloatingObject* floatingObject = it->get();
2524         LayoutUnit floatLogicalBottom = logicalBottomForFloat(floatingObject);
2525         ShapeOutsideInfo* shapeOutside = floatingObject->renderer()->shapeOutsideInfo();
2526         if (shapeOutside && (offsetMode == ShapeOutsideFloatShapeOffset)) {
2527             LayoutUnit shapeLogicalBottom = logicalTopForFloat(floatingObject) + marginBeforeForChild(floatingObject->renderer()) + shapeOutside->shapeLogicalBottom();
2528             // Use the shapeLogicalBottom unless it extends outside of the margin box, in which case it is clipped.
2529             if (shapeLogicalBottom < floatLogicalBottom)
2530                 floatLogicalBottom = shapeLogicalBottom;
2531         }
2532         if (floatLogicalBottom > logicalHeight)
2533             logicalBottom = logicalBottom ? min(floatLogicalBottom, logicalBottom) : floatLogicalBottom;
2534     }
2535
2536     return logicalBottom;
2537 }
2538
2539 bool RenderBlockFlow::hitTestFloats(const HitTestRequest& request, HitTestResult& result, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset)
2540 {
2541     if (!m_floatingObjects)
2542         return false;
2543
2544     LayoutPoint adjustedLocation = accumulatedOffset;
2545     if (isRenderView()) {
2546         adjustedLocation += toLayoutSize(toRenderView(this)->frameView()->scrollPosition());
2547     }
2548
2549     const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
2550     FloatingObjectSetIterator begin = floatingObjectSet.begin();
2551     for (FloatingObjectSetIterator it = floatingObjectSet.end(); it != begin;) {
2552         --it;
2553         FloatingObject* floatingObject = it->get();
2554         if (floatingObject->shouldPaint() && !floatingObject->renderer()->hasSelfPaintingLayer()) {
2555             LayoutUnit xOffset = xPositionForFloatIncludingMargin(floatingObject) - floatingObject->renderer()->x();
2556             LayoutUnit yOffset = yPositionForFloatIncludingMargin(floatingObject) - floatingObject->renderer()->y();
2557             LayoutPoint childPoint = flipFloatForWritingModeForChild(floatingObject, adjustedLocation + LayoutSize(xOffset, yOffset));
2558             if (floatingObject->renderer()->hitTest(request, result, locationInContainer, childPoint)) {
2559                 updateHitTestResult(result, locationInContainer.point() - toLayoutSize(childPoint));
2560                 return true;
2561             }
2562         }
2563     }
2564
2565     return false;
2566 }
2567
2568 void RenderBlockFlow::adjustForBorderFit(LayoutUnit x, LayoutUnit& left, LayoutUnit& right) const
2569 {
2570     RenderBlock::adjustForBorderFit(x, left, right);
2571     if (m_floatingObjects && style()->visibility() == VISIBLE) {
2572         const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
2573         FloatingObjectSetIterator end = floatingObjectSet.end();
2574         for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
2575             FloatingObject* floatingObject = it->get();
2576             // Only examine the object if our m_shouldPaint flag is set.
2577             if (floatingObject->shouldPaint()) {
2578                 LayoutUnit floatLeft = xPositionForFloatIncludingMargin(floatingObject) - floatingObject->renderer()->x();
2579                 LayoutUnit floatRight = floatLeft + floatingObject->renderer()->width();
2580                 left = min(left, floatLeft);
2581                 right = max(right, floatRight);
2582             }
2583         }
2584     }
2585 }
2586
2587 LayoutUnit RenderBlockFlow::logicalLeftFloatOffsetForLine(LayoutUnit logicalTop, LayoutUnit fixedOffset, LayoutUnit logicalHeight) const
2588 {
2589     if (m_floatingObjects && m_floatingObjects->hasLeftObjects())
2590         return m_floatingObjects->logicalLeftOffset(fixedOffset, logicalTop, logicalHeight);
2591
2592     return fixedOffset;
2593 }
2594
2595 LayoutUnit RenderBlockFlow::logicalRightFloatOffsetForLine(LayoutUnit logicalTop, LayoutUnit fixedOffset, LayoutUnit logicalHeight) const
2596 {
2597     if (m_floatingObjects && m_floatingObjects->hasRightObjects())
2598         return m_floatingObjects->logicalRightOffset(fixedOffset, logicalTop, logicalHeight);
2599
2600     return fixedOffset;
2601 }
2602
2603 GapRects RenderBlockFlow::inlineSelectionGaps(RenderBlock* rootBlock, const LayoutPoint& rootBlockPhysicalPosition, const LayoutSize& offsetFromRootBlock,
2604     LayoutUnit& lastLogicalTop, LayoutUnit& lastLogicalLeft, LayoutUnit& lastLogicalRight, const PaintInfo* paintInfo)
2605 {
2606     GapRects result;
2607
2608     bool containsStart = selectionState() == SelectionStart || selectionState() == SelectionBoth;
2609
2610     if (!firstLineBox()) {
2611         if (containsStart) {
2612             // Go ahead and update our lastLogicalTop to be the bottom of the block.  <hr>s or empty blocks with height can trip this
2613             // case.
2614             lastLogicalTop = rootBlock->blockDirectionOffset(offsetFromRootBlock) + logicalHeight();
2615             lastLogicalLeft = logicalLeftSelectionOffset(rootBlock, logicalHeight());
2616             lastLogicalRight = logicalRightSelectionOffset(rootBlock, logicalHeight());
2617         }
2618         return result;
2619     }
2620
2621     RootInlineBox* lastSelectedLine = 0;
2622     RootInlineBox* curr;
2623     for (curr = firstRootBox(); curr && !curr->hasSelectedChildren(); curr = curr->nextRootBox()) { }
2624
2625     // Now paint the gaps for the lines.
2626     for (; curr && curr->hasSelectedChildren(); curr = curr->nextRootBox()) {
2627         LayoutUnit selTop =  curr->selectionTopAdjustedForPrecedingBlock();
2628         LayoutUnit selHeight = curr->selectionHeightAdjustedForPrecedingBlock();
2629
2630         if (!containsStart && !lastSelectedLine && selectionState() != SelectionStart && selectionState() != SelectionBoth) {
2631             result.uniteCenter(blockSelectionGap(rootBlock, rootBlockPhysicalPosition, offsetFromRootBlock, lastLogicalTop,
2632                 lastLogicalLeft, lastLogicalRight, selTop, paintInfo));
2633         }
2634
2635         LayoutRect logicalRect(curr->logicalLeft(), selTop, curr->logicalWidth(), selTop + selHeight);
2636         logicalRect.move(isHorizontalWritingMode() ? offsetFromRootBlock : offsetFromRootBlock.transposedSize());
2637         LayoutRect physicalRect = rootBlock->logicalRectToPhysicalRect(rootBlockPhysicalPosition, logicalRect);
2638         if (!paintInfo || (isHorizontalWritingMode() && physicalRect.y() < paintInfo->rect.maxY() && physicalRect.maxY() > paintInfo->rect.y())
2639             || (!isHorizontalWritingMode() && physicalRect.x() < paintInfo->rect.maxX() && physicalRect.maxX() > paintInfo->rect.x()))
2640             result.unite(curr->lineSelectionGap(rootBlock, rootBlockPhysicalPosition, offsetFromRootBlock, selTop, selHeight, paintInfo));
2641
2642         lastSelectedLine = curr;
2643     }
2644
2645     if (containsStart && !lastSelectedLine) {
2646         // VisibleSelection must start just after our last line.
2647         lastSelectedLine = lastRootBox();
2648     }
2649
2650     if (lastSelectedLine && selectionState() != SelectionEnd && selectionState() != SelectionBoth) {
2651         // Go ahead and update our lastY to be the bottom of the last selected line.
2652         lastLogicalTop = rootBlock->blockDirectionOffset(offsetFromRootBlock) + lastSelectedLine->selectionBottom();
2653         lastLogicalLeft = logicalLeftSelectionOffset(rootBlock, lastSelectedLine->selectionBottom());
2654         lastLogicalRight = logicalRightSelectionOffset(rootBlock, lastSelectedLine->selectionBottom());
2655     }
2656     return result;
2657 }
2658
2659 LayoutUnit RenderBlockFlow::logicalLeftSelectionOffset(RenderBlock* rootBlock, LayoutUnit position)
2660 {
2661     LayoutUnit logicalLeft = logicalLeftOffsetForLine(position, false);
2662     if (logicalLeft == logicalLeftOffsetForContent())
2663         return RenderBlock::logicalLeftSelectionOffset(rootBlock, position);
2664
2665     RenderBlock* cb = this;
2666     while (cb != rootBlock) {
2667         logicalLeft += cb->logicalLeft();
2668         cb = cb->containingBlock();
2669     }
2670     return logicalLeft;
2671 }
2672
2673 LayoutUnit RenderBlockFlow::logicalRightSelectionOffset(RenderBlock* rootBlock, LayoutUnit position)
2674 {
2675     LayoutUnit logicalRight = logicalRightOffsetForLine(position, false);
2676     if (logicalRight == logicalRightOffsetForContent())
2677         return RenderBlock::logicalRightSelectionOffset(rootBlock, position);
2678
2679     RenderBlock* cb = this;
2680     while (cb != rootBlock) {
2681         logicalRight += cb->logicalLeft();
2682         cb = cb->containingBlock();
2683     }
2684     return logicalRight;
2685 }
2686
2687 template <typename CharacterType>
2688 static inline TextRun constructTextRunInternal(RenderObject* context, const Font& font, const CharacterType* characters, int length, RenderStyle* style, TextDirection direction, TextRun::ExpansionBehavior expansion)
2689 {
2690     ASSERT(style);
2691
2692     TextDirection textDirection = direction;
2693     bool directionalOverride = style->rtlOrdering() == VisualOrder;
2694
2695     TextRun run(characters, length, 0, 0, expansion, textDirection, directionalOverride);
2696     if (textRunNeedsRenderingContext(font))
2697         run.setRenderingContext(SVGTextRunRenderingContext::create(context));
2698
2699     return run;
2700 }
2701
2702 template <typename CharacterType>
2703 static inline TextRun constructTextRunInternal(RenderObject* context, const Font& font, const CharacterType* characters, int length, RenderStyle* style, TextDirection direction, TextRun::ExpansionBehavior expansion, TextRunFlags flags)
2704 {
2705     ASSERT(style);
2706
2707     TextDirection textDirection = direction;
2708     bool directionalOverride = style->rtlOrdering() == VisualOrder;
2709     if (flags != DefaultTextRunFlags) {
2710         if (flags & RespectDirection)
2711             textDirection = style->direction();
2712         if (flags & RespectDirectionOverride)
2713             directionalOverride |= isOverride(style->unicodeBidi());
2714     }
2715
2716     TextRun run(characters, length, 0, 0, expansion, textDirection, directionalOverride);
2717     if (textRunNeedsRenderingContext(font))
2718         run.setRenderingContext(SVGTextRunRenderingContext::create(context));
2719
2720     return run;
2721 }
2722
2723 TextRun RenderBlockFlow::constructTextRun(RenderObject* context, const Font& font, const LChar* characters, int length, RenderStyle* style, TextDirection direction, TextRun::ExpansionBehavior expansion)
2724 {
2725     return constructTextRunInternal(context, font, characters, length, style, direction, expansion);
2726 }
2727
2728 TextRun RenderBlockFlow::constructTextRun(RenderObject* context, const Font& font, const UChar* characters, int length, RenderStyle* style, TextDirection direction, TextRun::ExpansionBehavior expansion)
2729 {
2730     return constructTextRunInternal(context, font, characters, length, style, direction, expansion);
2731 }
2732
2733 TextRun RenderBlockFlow::constructTextRun(RenderObject* context, const Font& font, const RenderText* text, RenderStyle* style, TextDirection direction, TextRun::ExpansionBehavior expansion)
2734 {
2735     if (text->is8Bit())
2736         return constructTextRunInternal(context, font, text->characters8(), text->textLength(), style, direction, expansion);
2737     return constructTextRunInternal(context, font, text->characters16(), text->textLength(), style, direction, expansion);
2738 }
2739
2740 TextRun RenderBlockFlow::constructTextRun(RenderObject* context, const Font& font, const RenderText* text, unsigned offset, unsigned length, RenderStyle* style, TextDirection direction, TextRun::ExpansionBehavior expansion)
2741 {
2742     ASSERT(offset + length <= text->textLength());
2743     if (text->is8Bit())
2744         return constructTextRunInternal(context, font, text->characters8() + offset, length, style, direction, expansion);
2745     return constructTextRunInternal(context, font, text->characters16() + offset, length, style, direction, expansion);
2746 }
2747
2748 TextRun RenderBlockFlow::constructTextRun(RenderObject* context, const Font& font, const String& string, RenderStyle* style, TextDirection direction, TextRun::ExpansionBehavior expansion, TextRunFlags flags)
2749 {
2750     unsigned length = string.length();
2751     if (!length)
2752         return constructTextRunInternal(context, font, static_cast<const LChar*>(0), length, style, direction, expansion, flags);
2753     if (string.is8Bit())
2754         return constructTextRunInternal(context, font, string.characters8(), length, style, direction, expansion, flags);
2755     return constructTextRunInternal(context, font, string.characters16(), length, style, direction, expansion, flags);
2756 }
2757
2758 TextRun RenderBlockFlow::constructTextRun(RenderObject* context, const Font& font, const String& string, RenderStyle* style, TextRun::ExpansionBehavior expansion, TextRunFlags flags)
2759 {
2760     bool hasStrongDirectionality;
2761     return constructTextRun(context, font, string, style,
2762         determineDirectionality(string, hasStrongDirectionality),
2763         expansion, flags);
2764 }
2765
2766 TextRun RenderBlockFlow::constructTextRun(RenderObject* context, const Font& font, const RenderText* text, unsigned offset, unsigned length, RenderStyle* style, TextRun::ExpansionBehavior expansion)
2767 {
2768     ASSERT(offset + length <= text->textLength());
2769     TextRun run = text->is8Bit()
2770         ? constructTextRunInternal(context, font, text->characters8() + offset, length, style, LTR, expansion)
2771         : constructTextRunInternal(context, font, text->characters16() + offset, length, style, LTR, expansion);
2772     bool hasStrongDirectionality;
2773     run.setDirection(directionForRun(run, hasStrongDirectionality));
2774     return run;
2775 }
2776
2777 RootInlineBox* RenderBlockFlow::createRootInlineBox()
2778 {
2779     return new RootInlineBox(*this);
2780 }
2781
2782 void RenderBlockFlow::createOrDestroyMultiColumnFlowThreadIfNeeded()
2783 {
2784     if (!document().regionBasedColumnsEnabled())
2785         return;
2786
2787     bool needsFlowThread = style()->specifiesColumns();
2788     if (needsFlowThread != static_cast<bool>(multiColumnFlowThread())) {
2789         if (needsFlowThread) {
2790             RenderMultiColumnFlowThread* flowThread = RenderMultiColumnFlowThread::createAnonymous(document(), style());
2791             addChild(flowThread);
2792             flowThread->populate();
2793             RenderBlockFlowRareData& rareData = ensureRareData();
2794             ASSERT(!rareData.m_multiColumnFlowThread);
2795             rareData.m_multiColumnFlowThread = flowThread;
2796         } else {
2797             multiColumnFlowThread()->evacuateAndDestroy();
2798             ASSERT(!multiColumnFlowThread());
2799         }
2800     }
2801 }
2802
2803 RenderBlockFlow::RenderBlockFlowRareData& RenderBlockFlow::ensureRareData()
2804 {
2805     if (m_rareData)
2806         return *m_rareData;
2807
2808     m_rareData = adoptPtr(new RenderBlockFlowRareData(this));
2809     return *m_rareData;
2810 }
2811
2812 } // namespace WebCore