*** DO NOT LAND *** Attempt to understand Regions complexity

Source/core/rendering/RenderMultiColumnFlowThread.cpp

-/*
- * Copyright (C) 2012 Apple Inc.  All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
- * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
- * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
- * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
- * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
- * PROFITS; OR BUSINESS IN..0TERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
- * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF  ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#include "config.h"
-#include "core/rendering/RenderMultiColumnFlowThread.h"
-
-#include "core/rendering/RenderMultiColumnBlock.h"
-#include "core/rendering/RenderMultiColumnSet.h"
-
-namespace WebCore {
-
-RenderMultiColumnFlowThread::RenderMultiColumnFlowThread()
-{
-    setFlowThreadState(InsideInFlowThread);
-}
-
-RenderMultiColumnFlowThread::~RenderMultiColumnFlowThread()
-{
-}
-
-RenderMultiColumnFlowThread* RenderMultiColumnFlowThread::createAnonymous(Document* document)
-{
-    RenderMultiColumnFlowThread* renderer = new RenderMultiColumnFlowThread();
-    renderer->setDocumentForAnonymous(document);
-    return renderer;
-}
-
-const char* RenderMultiColumnFlowThread::renderName() const
-{
-    return "RenderMultiColumnFlowThread";
-}
-
-void RenderMultiColumnFlowThread::computeLogicalHeight(LayoutUnit logicalHeight, LayoutUnit logicalTop, LogicalExtentComputedValues& computedValues) const
-{
-    // We simply remain at our intrinsic height.
-    computedValues.m_extent = logicalHeight;
-    computedValues.m_position = logicalTop;
-}
-
-LayoutUnit RenderMultiColumnFlowThread::initialLogicalWidth() const
-{
-    RenderMultiColumnBlock* parentBlock = toRenderMultiColumnBlock(parent());
-    return parentBlock->columnWidth();
-}
-
-void RenderMultiColumnFlowThread::autoGenerateRegionsToBlockOffset(LayoutUnit /*offset*/)
-{
-    // This function ensures we have the correct column set information at all times.
-    // For a simple multi-column layout in continuous media, only one column set child is required.
-    // Once a column is nested inside an enclosing pagination context, the number of column sets
-    // required becomes 2n-1, where n is the total number of nested pagination contexts. For example:
-    //
-    // Column layout with no enclosing pagination model = 2 * 1 - 1 = 1 column set.
-    // Columns inside pages = 2 * 2 - 1 = 3 column sets (bottom of first page, all the subsequent pages, then the last page).
-    // Columns inside columns inside pages = 2 * 3 - 1 = 5 column sets.
-    //
-    // In addition, column spans will force a column set to "split" into before/after sets around the spanning element.
-    //
-    // Finally, we will need to deal with columns inside regions. If regions have variable widths, then there will need
-    // to be unique column sets created inside any region whose width is different from its surrounding regions. This is
-    // actually pretty similar to the spanning case, in that we break up the column sets whenever the width varies.
-    //
-    // FIXME: For now just make one column set. This matches the old multi-column code.
-    // Right now our goal is just feature parity with the old multi-column code so that we can switch over to the
-    // new code as soon as possible.
-    RenderMultiColumnSet* firstSet = toRenderMultiColumnSet(firstRegion());
-    if (firstSet)
-        return;
-
-    invalidateRegions();
-
-    RenderMultiColumnBlock* parentBlock = toRenderMultiColumnBlock(parent());
-    firstSet = RenderMultiColumnSet::createAnonymous(this);
-    firstSet->setStyle(RenderStyle::createAnonymousStyleWithDisplay(parentBlock->style(), BLOCK));
-    parentBlock->RenderBlock::addChild(firstSet);
-
-    // Even though we aren't placed yet, we can go ahead and set up our size. At this point we're
-    // typically in the middle of laying out the thread, attempting to paginate, and we need to do
-    // some rudimentary "layout" of the set now, so that pagination will work.
-    firstSet->prepareForLayout();
-
-    validateRegions();
-}
-
-void RenderMultiColumnFlowThread::setPageBreak(LayoutUnit offset, LayoutUnit spaceShortage)
-{
-    if (RenderMultiColumnSet* multicolSet = toRenderMultiColumnSet(regionAtBlockOffset(offset)))
-        multicolSet->recordSpaceShortage(spaceShortage);
-}
-
-void RenderMultiColumnFlowThread::updateMinimumPageHeight(LayoutUnit offset, LayoutUnit minHeight)
-{
-    if (RenderMultiColumnSet* multicolSet = toRenderMultiColumnSet(regionAtBlockOffset(offset)))
-        multicolSet->updateMinimumColumnHeight(minHeight);
-}
-
-}