Source/WebCore/platform/graphics/texmap/TextureMapperTiledBackingStore.cpp

/*
 Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies)

 This library is free software; you can redistribute it and/or
 modify it under the terms of the GNU Library General Public
 License as published by the Free Software Foundation; either
 version 2 of the License, or (at your option) any later version.

 This library is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 Library General Public License for more details.

 You should have received a copy of the GNU Library General Public License
 along with this library; see the file COPYING.LIB.  If not, write to
 the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 Boston, MA 02110-1301, USA.
 */

#include "config.h"

#include "TextureMapperTiledBackingStore.h"

#include "ImageBuffer.h"
#include "ImageObserver.h"
#include "TextureMapper.h"

namespace WebCore {

class GraphicsLayer;

void TextureMapperTiledBackingStore::updateContentsFromImageIfNeeded(TextureMapper& textureMapper)
{
    if (!m_image)
        return;

    updateContents(textureMapper, m_image.get(), m_image->size(), enclosingIntRect(m_image->rect()));

    if (m_image->imageObserver())
        m_image->imageObserver()->didDraw(*m_image);
    m_image = nullptr;
}

TransformationMatrix TextureMapperTiledBackingStore::adjustedTransformForRect(const FloatRect& targetRect)
{
    return TransformationMatrix::rectToRect(rect(), targetRect);
}

void TextureMapperTiledBackingStore::paintToTextureMapper(TextureMapper& textureMapper, const FloatRect& targetRect, const TransformationMatrix& transform, float opacity)
{
    updateContentsFromImageIfNeeded(textureMapper);
    TransformationMatrix adjustedTransform = transform * adjustedTransformForRect(targetRect);
    for (auto& tile : m_tiles)
        tile.paint(textureMapper, adjustedTransform, opacity, calculateExposedTileEdges(rect(), tile.rect()));
}

void TextureMapperTiledBackingStore::drawBorder(TextureMapper& textureMapper, const Color& borderColor, float borderWidth, const FloatRect& targetRect, const TransformationMatrix& transform)
{
    TransformationMatrix adjustedTransform = transform * adjustedTransformForRect(targetRect);
    for (auto& tile : m_tiles)
        textureMapper.drawBorder(borderColor, borderWidth, tile.rect(), adjustedTransform);
}

void TextureMapperTiledBackingStore::drawRepaintCounter(TextureMapper& textureMapper, int repaintCount, const Color& borderColor, const FloatRect& targetRect, const TransformationMatrix& transform)
{
    TransformationMatrix adjustedTransform = transform * adjustedTransformForRect(targetRect);
    for (auto& tile : m_tiles)
        textureMapper.drawNumber(repaintCount, borderColor, tile.rect().location(), adjustedTransform);
}

void TextureMapperTiledBackingStore::updateContentsScale(float scale)
{
    if (m_contentsScale == scale)
        return;

    m_isScaleDirty = true;
    m_contentsScale = scale;
}

void TextureMapperTiledBackingStore::createOrDestroyTilesIfNeeded(const FloatSize& size, const IntSize& tileSize, bool hasAlpha)
{
    if (size == m_size && !m_isScaleDirty)
        return;

    m_size = size;
    m_isScaleDirty = false;

    FloatSize scaledSize(m_size);
    if (!m_image)
        scaledSize.scale(m_contentsScale);

    Vector<FloatRect> tileRectsToAdd;
    Vector<int> tileIndicesToRemove;
    static const size_t TileEraseThreshold = 6;

    // This method recycles tiles. We check which tiles we need to add, which to remove, and use as many
    // removable tiles as replacement for new tiles when possible.
    for (float y = 0; y < scaledSize.height(); y += tileSize.height()) {
        for (float x = 0; x < scaledSize.width(); x += tileSize.width()) {
            FloatRect tileRect(x, y, tileSize.width(), tileSize.height());
            tileRect.intersect(rect());
            tileRectsToAdd.append(tileRect);
        }
    }

    // Check which tiles need to be removed, and which already exist.
    for (int i = m_tiles.size() - 1; i >= 0; --i) {
        FloatRect oldTile = m_tiles[i].rect();
        bool existsAlready = false;

        for (int j = tileRectsToAdd.size() - 1; j >= 0; --j) {
            FloatRect newTile = tileRectsToAdd[j];
            if (oldTile != newTile)
                continue;

            // A tile that we want to add already exists, no need to add or remove it.
            existsAlready = true;
            tileRectsToAdd.remove(j);
            break;
        }

        // This tile is not needed.
        if (!existsAlready)
            tileIndicesToRemove.append(i);
    }

    // Recycle removable tiles to be used for newly requested tiles.
    for (auto& rect : tileRectsToAdd) {
        if (!tileIndicesToRemove.isEmpty()) {
            // We recycle an existing tile for usage with a new tile rect.
            TextureMapperTile& tile = m_tiles[tileIndicesToRemove.last()];
            tileIndicesToRemove.removeLast();
            tile.setRect(rect);

            if (tile.texture())
                tile.texture()->reset(enclosingIntRect(tile.rect()).size(), hasAlpha ? BitmapTexture::SupportsAlpha : 0);
            continue;
        }

        m_tiles.append(TextureMapperTile(rect));
    }

    // Remove unnecessary tiles, if they weren't recycled.
    // We use a threshold to make sure we don't create/destroy tiles too eagerly.
    for (auto& index : tileIndicesToRemove) {
        if (m_tiles.size() <= TileEraseThreshold)
            break;
        m_tiles.remove(index);
    }
}

void TextureMapperTiledBackingStore::updateContents(TextureMapper& textureMapper, Image* image, const FloatSize& totalSize, const IntRect& dirtyRect)
{
    createOrDestroyTilesIfNeeded(totalSize, textureMapper.maxTextureSize(), !image->currentFrameKnownToBeOpaque());
    for (auto& tile : m_tiles)
        tile.updateContents(textureMapper, image, dirtyRect);
}

void TextureMapperTiledBackingStore::updateContents(TextureMapper& textureMapper, GraphicsLayer* sourceLayer, const FloatSize& totalSize, const IntRect& dirtyRect)
{
    createOrDestroyTilesIfNeeded(totalSize, textureMapper.maxTextureSize(), true);
    for (auto& tile : m_tiles)
        tile.updateContents(textureMapper, sourceLayer, dirtyRect, m_contentsScale);
}

} // namespace WebCore