third_party/WebKit/Source/core/paint/GridPainter.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/paint/GridPainter.h"

#include "core/layout/LayoutGrid.h"
#include "core/paint/BlockPainter.h"
#include "core/paint/PaintInfo.h"
#include <algorithm>

namespace blink {

static GridSpan dirtiedGridAreas(const Vector<LayoutUnit>& coordinates,
                                 LayoutUnit start,
                                 LayoutUnit end) {
  // This function does a binary search over the coordinates.
  // This doesn't work with grid items overflowing their grid areas, but that is
  // managed with m_gridItemsOverflowingGridArea.

  size_t startGridAreaIndex =
      std::upper_bound(coordinates.begin(), coordinates.end() - 1, start) -
      coordinates.begin();
  if (startGridAreaIndex > 0)
    --startGridAreaIndex;

  size_t endGridAreaIndex =
      std::upper_bound(coordinates.begin() + startGridAreaIndex,
                       coordinates.end() - 1, end) -
      coordinates.begin();
  if (endGridAreaIndex > 0)
    --endGridAreaIndex;

  // GridSpan stores lines' indexes (not tracks' indexes).
  return GridSpan::translatedDefiniteGridSpan(startGridAreaIndex,
                                              endGridAreaIndex + 1);
}

// Helper for the sorting of grid items following order-modified document order.
// See http://www.w3.org/TR/css-flexbox/#order-modified-document-order
static inline bool compareOrderModifiedDocumentOrder(
    const std::pair<LayoutBox*, size_t>& firstItem,
    const std::pair<LayoutBox*, size_t>& secondItem) {
  return firstItem.second < secondItem.second;
}

void GridPainter::paintChildren(const PaintInfo& paintInfo,
                                const LayoutPoint& paintOffset) {
  DCHECK(!m_layoutGrid.needsLayout());

  LayoutRect localVisualRect = LayoutRect(paintInfo.cullRect().m_rect);
  localVisualRect.moveBy(-paintOffset);

  Vector<LayoutUnit> columnPositions = m_layoutGrid.columnPositions();
  if (!m_layoutGrid.styleRef().isLeftToRightDirection()) {
    // Translate columnPositions in RTL as we need the physical coordinates of
    // the columns in order to call dirtiedGridAreas().
    for (size_t i = 0; i < columnPositions.size(); i++)
      columnPositions[i] =
          m_layoutGrid.translateRTLCoordinate(columnPositions[i]);
    // We change the order of tracks in columnPositions, as in RTL the leftmost
    // track will be the last one.
    std::sort(columnPositions.begin(), columnPositions.end());
  }

  GridSpan dirtiedColumns = dirtiedGridAreas(
      columnPositions, localVisualRect.x(), localVisualRect.maxX());
  GridSpan dirtiedRows = dirtiedGridAreas(
      m_layoutGrid.rowPositions(), localVisualRect.y(), localVisualRect.maxY());

  if (!m_layoutGrid.styleRef().isLeftToRightDirection()) {
    // As we changed the order of tracks previously, we need to swap the dirtied
    // columns in RTL.
    size_t lastLine = columnPositions.size() - 1;
    dirtiedColumns = GridSpan::translatedDefiniteGridSpan(
        lastLine - dirtiedColumns.endLine(),
        lastLine - dirtiedColumns.startLine());
  }

  Vector<std::pair<LayoutBox*, size_t>> gridItemsToBePainted;

  for (const auto& row : dirtiedRows) {
    for (const auto& column : dirtiedColumns) {
      const Vector<LayoutBox*, 1>& children =
          m_layoutGrid.gridCell(row, column);
      for (auto* child : children)
        gridItemsToBePainted.append(
            std::make_pair(child, m_layoutGrid.paintIndexForGridItem(child)));
    }
  }

  for (auto* item : m_layoutGrid.itemsOverflowingGridArea()) {
    if (item->frameRect().intersects(localVisualRect))
      gridItemsToBePainted.append(
          std::make_pair(item, m_layoutGrid.paintIndexForGridItem(item)));
  }

  std::stable_sort(gridItemsToBePainted.begin(), gridItemsToBePainted.end(),
                   compareOrderModifiedDocumentOrder);

  LayoutBox* previous = 0;
  for (const auto& gridItemAndPaintIndex : gridItemsToBePainted) {
    // We might have duplicates because of spanning children are included in all
    // cells they span.  Skip them here to avoid painting items several times.
    LayoutBox* current = gridItemAndPaintIndex.first;
    if (current == previous)
      continue;

    BlockPainter(m_layoutGrid)
        .paintAllChildPhasesAtomically(*current, paintInfo, paintOffset);
    previous = current;
  }
}

}  // namespace blink