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

// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "core/layout/LayoutPagedFlowThread.h"

#include "core/layout/LayoutMultiColumnSet.h"

namespace blink {

LayoutPagedFlowThread* LayoutPagedFlowThread::createAnonymous(
    Document& document,
    const ComputedStyle& parentStyle) {
  LayoutPagedFlowThread* pagedFlowThread = new LayoutPagedFlowThread();
  pagedFlowThread->setDocumentForAnonymous(&document);
  pagedFlowThread->setStyle(ComputedStyle::createAnonymousStyleWithDisplay(
      parentStyle, EDisplay::Block));
  return pagedFlowThread;
}

int LayoutPagedFlowThread::pageCount() {
  if (LayoutMultiColumnSet* columnSet = firstMultiColumnSet())
    return columnSet->actualColumnCount();
  return 1;
}

bool LayoutPagedFlowThread::needsNewWidth() const {
  return progressionIsInline() !=
         pagedBlockFlow()->style()->hasInlinePaginationAxis();
}

void LayoutPagedFlowThread::updateLogicalWidth() {
  // As long as we inherit from LayoutMultiColumnFlowThread, we need to bypass
  // its implementation here. We're not split into columns, so the flow thread
  // width will just be whatever is available in the containing block.
  LayoutFlowThread::updateLogicalWidth();
}

void LayoutPagedFlowThread::layout() {
  // There should either be zero or one of those for paged layout.
  DCHECK(firstMultiColumnBox() == lastMultiColumnBox());
  setProgressionIsInline(pagedBlockFlow()->style()->hasInlinePaginationAxis());
  LayoutMultiColumnFlowThread::layout();

  LayoutMultiColumnSet* columnSet = firstMultiColumnSet();
  if (!columnSet)
    return;
  LayoutUnit pageLogicalHeight =
      columnSet->pageLogicalHeightForOffset(LayoutUnit());
  if (!pageLogicalHeight)
    return;  // Page height not calculated yet. Happens in the first layout pass
             // when height is auto.
  // Ensure uniform page height. We don't want the last page to be shorter than
  // the others, or it'll be impossible to scroll that whole page into view.
  LayoutUnit paddedLogicalBottomInFlowThread = pageLogicalHeight * pageCount();
  ASSERT(paddedLogicalBottomInFlowThread >=
         columnSet->logicalBottomInFlowThread());
  columnSet->endFlow(paddedLogicalBottomInFlowThread);
}

}  // namespace blink