1 /* 2 * Copyright (C) 2012 Apple Inc. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY 14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE COMPUTER, INC. OR 17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 20 * PROFITS; OR BUSINESS IN..0TERRUPTION) HOWEVER CAUSED AND ON ANY THEORY 21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26 #include "config.h" 27 #include "core/rendering/RenderMultiColumnFlowThread.h" 28 29 #include "core/rendering/RenderMultiColumnSet.h" 30 31 namespace WebCore { 32 33 RenderMultiColumnFlowThread::RenderMultiColumnFlowThread() 34 : m_columnCount(1) 35 , m_columnHeightAvailable(0) 36 , m_inBalancingPass(false) 37 , m_needsColumnHeightsRecalculation(false) 38 { 39 setFlowThreadState(InsideInFlowThread); 40 } 41 42 RenderMultiColumnFlowThread::~RenderMultiColumnFlowThread() 43 { 44 } 45 46 RenderMultiColumnFlowThread* RenderMultiColumnFlowThread::createAnonymous(Document& document, RenderStyle* parentStyle) 47 { 48 RenderMultiColumnFlowThread* renderer = new RenderMultiColumnFlowThread(); 49 renderer->setDocumentForAnonymous(&document); 50 renderer->setStyle(RenderStyle::createAnonymousStyleWithDisplay(parentStyle, BLOCK)); 51 return renderer; 52 } 53 54 RenderMultiColumnSet* RenderMultiColumnFlowThread::firstMultiColumnSet() const 55 { 56 for (RenderObject* sibling = nextSibling(); sibling; sibling = sibling->nextSibling()) { 57 if (sibling->isRenderMultiColumnSet()) 58 return toRenderMultiColumnSet(sibling); 59 } 60 return 0; 61 } 62 63 RenderMultiColumnSet* RenderMultiColumnFlowThread::lastMultiColumnSet() const 64 { 65 for (RenderObject* sibling = multiColumnBlockFlow()->lastChild(); sibling; sibling = sibling->previousSibling()) { 66 if (sibling->isRenderMultiColumnSet()) 67 return toRenderMultiColumnSet(sibling); 68 } 69 return 0; 70 } 71 72 void RenderMultiColumnFlowThread::addChild(RenderObject* newChild, RenderObject* beforeChild) 73 { 74 RenderBlockFlow::addChild(newChild, beforeChild); 75 if (firstMultiColumnSet()) 76 return; 77 78 // For now we only create one column set. It's created as soon as the multicol container gets 79 // any content at all. 80 RenderMultiColumnSet* newSet = RenderMultiColumnSet::createAnonymous(this, multiColumnBlockFlow()->style()); 81 82 // Need to skip RenderBlockFlow's implementation of addChild(), or we'd get redirected right 83 // back here. 84 multiColumnBlockFlow()->RenderBlock::addChild(newSet); 85 86 invalidateRegions(); 87 } 88 89 void RenderMultiColumnFlowThread::populate() 90 { 91 RenderBlockFlow* multicolContainer = multiColumnBlockFlow(); 92 ASSERT(!nextSibling()); 93 // Reparent children preceding the flow thread into the flow thread. It's multicol content 94 // now. At this point there's obviously nothing after the flow thread, but renderers (column 95 // sets and spanners) will be inserted there as we insert elements into the flow thread. 96 multicolContainer->moveChildrenTo(this, multicolContainer->firstChild(), this, true); 97 } 98 99 void RenderMultiColumnFlowThread::evacuateAndDestroy() 100 { 101 RenderBlockFlow* multicolContainer = multiColumnBlockFlow(); 102 103 // Remove all sets. 104 while (RenderMultiColumnSet* columnSet = firstMultiColumnSet()) 105 columnSet->destroy(); 106 107 ASSERT(!previousSibling()); 108 ASSERT(!nextSibling()); 109 110 // Finally we can promote all flow thread's children. Before we move them to the flow thread's 111 // container, we need to unregister the flow thread, so that they aren't just re-added again to 112 // the flow thread that we're trying to empty. 113 multicolContainer->resetMultiColumnFlowThread(); 114 moveAllChildrenTo(multicolContainer, true); 115 116 // FIXME: it's scary that neither destroy() nor the move*Children* methods take care of this, 117 // and instead leave you with dangling root line box pointers. But since this is how it is done 118 // in other parts of the code that deal with reparenting renderers, let's do the cleanup on our 119 // own here as well. 120 deleteLineBoxTree(); 121 122 destroy(); 123 } 124 125 LayoutSize RenderMultiColumnFlowThread::columnOffset(const LayoutPoint& point) const 126 { 127 if (!hasValidRegionInfo()) 128 return LayoutSize(0, 0); 129 130 LayoutPoint flowThreadPoint(point); 131 flipForWritingMode(flowThreadPoint); 132 LayoutUnit blockOffset = isHorizontalWritingMode() ? flowThreadPoint.y() : flowThreadPoint.x(); 133 RenderRegion* renderRegion = regionAtBlockOffset(blockOffset); 134 if (!renderRegion) 135 return LayoutSize(0, 0); 136 return toRenderMultiColumnSet(renderRegion)->flowThreadTranslationAtOffset(blockOffset); 137 } 138 139 bool RenderMultiColumnFlowThread::needsNewWidth() const 140 { 141 LayoutUnit newWidth; 142 unsigned dummyColumnCount; // We only care if used column-width changes. 143 calculateColumnCountAndWidth(newWidth, dummyColumnCount); 144 return newWidth != logicalWidth(); 145 } 146 147 void RenderMultiColumnFlowThread::layoutColumns(bool relayoutChildren, SubtreeLayoutScope& layoutScope) 148 { 149 if (relayoutChildren) 150 layoutScope.setChildNeedsLayout(this); 151 152 if (!needsLayout()) { 153 // Just before the multicol container (our parent RenderBlockFlow) finishes laying out, it 154 // will call recalculateColumnHeights() on us unconditionally, but we only want that method 155 // to do any work if we actually laid out the flow thread. Otherwise, the balancing 156 // machinery would kick in needlessly, and trigger additional layout passes. Furthermore, we 157 // actually depend on a proper flowthread layout pass in order to do balancing, since it's 158 // flowthread layout that sets up content runs. 159 m_needsColumnHeightsRecalculation = false; 160 return; 161 } 162 163 for (RenderMultiColumnSet* columnSet = firstMultiColumnSet(); columnSet; columnSet = columnSet->nextSiblingMultiColumnSet()) { 164 if (!m_inBalancingPass) { 165 // This is the initial layout pass. We need to reset the column height, because contents 166 // typically have changed. 167 columnSet->resetColumnHeight(); 168 } 169 } 170 171 invalidateRegions(); 172 m_needsColumnHeightsRecalculation = requiresBalancing(); 173 layout(); 174 } 175 176 bool RenderMultiColumnFlowThread::recalculateColumnHeights() 177 { 178 // All column sets that needed layout have now been laid out, so we can finally validate them. 179 validateRegions(); 180 181 if (!m_needsColumnHeightsRecalculation) 182 return false; 183 184 // Column heights may change here because of balancing. We may have to do multiple layout 185 // passes, depending on how the contents is fitted to the changed column heights. In most 186 // cases, laying out again twice or even just once will suffice. Sometimes we need more 187 // passes than that, though, but the number of retries should not exceed the number of 188 // columns, unless we have a bug. 189 bool needsRelayout = false; 190 for (RenderMultiColumnSet* multicolSet = firstMultiColumnSet(); multicolSet; multicolSet = multicolSet->nextSiblingMultiColumnSet()) { 191 needsRelayout |= multicolSet->recalculateColumnHeight(m_inBalancingPass ? RenderMultiColumnSet::StretchBySpaceShortage : RenderMultiColumnSet::GuessFromFlowThreadPortion); 192 if (needsRelayout) { 193 // Once a column set gets a new column height, that column set and all successive column 194 // sets need to be laid out over again, since their logical top will be affected by 195 // this, and therefore their column heights may change as well, at least if the multicol 196 // height is constrained. 197 multicolSet->setChildNeedsLayout(MarkOnlyThis); 198 } 199 } 200 201 if (needsRelayout) 202 setChildNeedsLayout(MarkOnlyThis); 203 204 m_inBalancingPass = needsRelayout; 205 return needsRelayout; 206 } 207 208 void RenderMultiColumnFlowThread::calculateColumnCountAndWidth(LayoutUnit& width, unsigned& count) const 209 { 210 RenderBlock* columnBlock = multiColumnBlockFlow(); 211 const RenderStyle* columnStyle = columnBlock->style(); 212 LayoutUnit availableWidth = columnBlock->contentLogicalWidth(); 213 LayoutUnit columnGap = columnBlock->columnGap(); 214 LayoutUnit computedColumnWidth = max<LayoutUnit>(1, LayoutUnit(columnStyle->columnWidth())); 215 unsigned computedColumnCount = max<int>(1, columnStyle->columnCount()); 216 217 ASSERT(!columnStyle->hasAutoColumnCount() || !columnStyle->hasAutoColumnWidth()); 218 if (columnStyle->hasAutoColumnWidth() && !columnStyle->hasAutoColumnCount()) { 219 count = computedColumnCount; 220 width = std::max<LayoutUnit>(0, (availableWidth - ((count - 1) * columnGap)) / count); 221 } else if (!columnStyle->hasAutoColumnWidth() && columnStyle->hasAutoColumnCount()) { 222 count = std::max<LayoutUnit>(1, (availableWidth + columnGap) / (computedColumnWidth + columnGap)); 223 width = ((availableWidth + columnGap) / count) - columnGap; 224 } else { 225 count = std::max<LayoutUnit>(std::min<LayoutUnit>(computedColumnCount, (availableWidth + columnGap) / (computedColumnWidth + columnGap)), 1); 226 width = ((availableWidth + columnGap) / count) - columnGap; 227 } 228 } 229 230 const char* RenderMultiColumnFlowThread::renderName() const 231 { 232 return "RenderMultiColumnFlowThread"; 233 } 234 235 void RenderMultiColumnFlowThread::addRegionToThread(RenderRegion* renderRegion) 236 { 237 RenderMultiColumnSet* columnSet = toRenderMultiColumnSet(renderRegion); 238 if (RenderMultiColumnSet* nextSet = columnSet->nextSiblingMultiColumnSet()) { 239 RenderRegionList::iterator it = m_regionList.find(nextSet); 240 ASSERT(it != m_regionList.end()); 241 m_regionList.insertBefore(it, columnSet); 242 } else { 243 m_regionList.add(columnSet); 244 } 245 renderRegion->setIsValid(true); 246 } 247 248 void RenderMultiColumnFlowThread::willBeRemovedFromTree() 249 { 250 // Detach all column sets from the flow thread. Cannot destroy them at this point, since they 251 // are siblings of this object, and there may be pointers to this object's sibling somewhere 252 // further up on the call stack. 253 for (RenderMultiColumnSet* columnSet = firstMultiColumnSet(); columnSet; columnSet = columnSet->nextSiblingMultiColumnSet()) 254 columnSet->detachRegion(); 255 multiColumnBlockFlow()->resetMultiColumnFlowThread(); 256 RenderFlowThread::willBeRemovedFromTree(); 257 } 258 259 void RenderMultiColumnFlowThread::computeLogicalHeight(LayoutUnit logicalHeight, LayoutUnit logicalTop, LogicalExtentComputedValues& computedValues) const 260 { 261 // We simply remain at our intrinsic height. 262 computedValues.m_extent = logicalHeight; 263 computedValues.m_position = logicalTop; 264 } 265 266 void RenderMultiColumnFlowThread::updateLogicalWidth() 267 { 268 LayoutUnit columnWidth; 269 calculateColumnCountAndWidth(columnWidth, m_columnCount); 270 setLogicalWidth(columnWidth); 271 } 272 273 void RenderMultiColumnFlowThread::layout() 274 { 275 RenderFlowThread::layout(); 276 if (RenderMultiColumnSet* lastSet = lastMultiColumnSet()) 277 lastSet->expandToEncompassFlowThreadContentsIfNeeded(); 278 } 279 280 void RenderMultiColumnFlowThread::setPageBreak(LayoutUnit offset, LayoutUnit spaceShortage) 281 { 282 // Only positive values are interesting (and allowed) here. Zero space shortage may be reported 283 // when we're at the top of a column and the element has zero height. Ignore this, and also 284 // ignore any negative values, which may occur when we set an early break in order to honor 285 // widows in the next column. 286 if (spaceShortage <= 0) 287 return; 288 289 if (RenderMultiColumnSet* multicolSet = toRenderMultiColumnSet(regionAtBlockOffset(offset))) 290 multicolSet->recordSpaceShortage(spaceShortage); 291 } 292 293 void RenderMultiColumnFlowThread::updateMinimumPageHeight(LayoutUnit offset, LayoutUnit minHeight) 294 { 295 if (RenderMultiColumnSet* multicolSet = toRenderMultiColumnSet(regionAtBlockOffset(offset))) 296 multicolSet->updateMinimumColumnHeight(minHeight); 297 } 298 299 RenderRegion* RenderMultiColumnFlowThread::regionAtBlockOffset(LayoutUnit /*offset*/) const 300 { 301 // For now there's only one column set, so this is easy: 302 return firstMultiColumnSet(); 303 } 304 305 bool RenderMultiColumnFlowThread::addForcedRegionBreak(LayoutUnit offset, RenderObject* /*breakChild*/, bool /*isBefore*/, LayoutUnit* offsetBreakAdjustment) 306 { 307 if (RenderMultiColumnSet* multicolSet = toRenderMultiColumnSet(regionAtBlockOffset(offset))) { 308 multicolSet->addContentRun(offset); 309 if (offsetBreakAdjustment) 310 *offsetBreakAdjustment = pageLogicalHeightForOffset(offset) ? pageRemainingLogicalHeightForOffset(offset, IncludePageBoundary) : LayoutUnit(); 311 return true; 312 } 313 return false; 314 } 315 316 bool RenderMultiColumnFlowThread::isPageLogicalHeightKnown() const 317 { 318 if (RenderMultiColumnSet* columnSet = lastMultiColumnSet()) 319 return columnSet->pageLogicalHeight(); 320 return false; 321 } 322 323 } 324