okular/core/tilesmanager_p.h

/***************************************************************************
 *   Copyright (C) 2012 by Mailson Menezes <mailson@gmail.com>             *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 ***************************************************************************/

#ifndef _OKULAR_TILES_MANAGER_P_H_
#define _OKULAR_TILES_MANAGER_P_H_

#include "okular_export.h"
#include "area.h"

class QPixmap;

namespace Okular {

class Tile;

/**
 * Node in the quadtree structure used by the tiles manager to store tiles.
 *
 * Except for the first level, the tiles manager stores tiles in a quadtree
 * structure.
 * Each node stores the pixmap of a tile and its location on the page.
 * There's a limit on the size of the pixmaps (TILES_MAXSIZE, defined in
 * tilesmanager.cpp), and tiles that are bigger than that value are split into
 * four children tiles, which are stored as children of the original tile.
 * If children tiles are still too big, they are recursively split again.
 * If the zoom level changes and a big tile goes below the limit, it is merged
 * back into a leaf tile.
 */
class TileNode
{
    public:
        TileNode();

        bool isValid() const;

        /**
         * Location on the page in normalized coords
         */
        NormalizedRect rect;

        /**
         * Associated pixmap or NULL if not present
         *
         * For each node, it is guaranteed that there's no more than one pixmap
         * along the path from the root to the node itself.
         * In fact, it is very frequent that a leaf node has no pixmap and one
         * of its ancestors has. Such a situation shows, for example, when the
         * parent tile still has a dirty tile from a previous lower zoom level.
         */
        QPixmap *pixmap;

        /**
         * Rotation of this individual tile.
         *
         * A rotation to the page does not immediately rotates the pixmaps in
         * cache. This operation happens when pixmaps are going to be used.
         */
        Rotation rotation;

        /**
         * Whether the tile needs to be repainted (after a zoom or rotation)
         * If a tile doesn't have a pixmap but all its children are updated
         * (dirty = false), the parent tile is also considered updated.
         */
        bool dirty;

        /**
         * Distance between the tile and the viewport.
         * This is used by the evicting algorithm.
         */
        double distance;

        /**
         * Children tiles
         * When a tile is split into multiple tiles, they're added as children.
         * nTiles can be either 0 (in leaf tiles) or 4 (in split tiles).
         */
        TileNode *tiles;
        int nTiles;
        TileNode *parent;
};

/**
 * @short Tiles management
 *
 * This class has direct access to all tiles and handles how they should be
 * stored, deleted and retrieved. Each tiles manager only handles one page.
 *
 * The tiles manager is a tree of tiles. At first the page is divided in a 4x4
 * grid of 16 tiles. Then each of these tiles can be recursively split in 4
 * subtiles so that we keep the size of each pixmap inside a safe interval.
 */
class TilesManager
{
    public:
        enum TileLeaf
        {
            TerminalTile,     ///< Return tiles without children
            PixmapTile        ///< Return only tiles with pixmap
        };

        TilesManager( int pageNumber, int width, int height, Rotation rotation = Rotation0 );
        ~TilesManager();

        /**
         * Sets the pixmap of the tiles covered by @p rect (which represents
         * the location of @p pixmap on the page).
         * @p pixmap may cover an area which contains multiple tiles. So each
         * tile we get a cropped part of the @p pixmap.
         *
         * Also it checks the dimensions of the given parameters against the
         * current request as to avoid setting pixmaps of late requests.
         */
        void setPixmap( const QPixmap *pixmap, const NormalizedRect &rect );

        /**
         * Checks whether all tiles intersecting with @p rect are available.
         * Returns false if at least one tile needs to be repainted (the tile
         * is dirty).
         */
        bool hasPixmap( const NormalizedRect &rect );

        /**
         * Returns a list of all tiles intersecting with @p rect.
         *
         * As to avoid requests of big areas, each traversed tile is checked
         * for its size and split if necessary.
         *
         * @param tileLeaf Indicate the type of tile to return
         */
        QList<Tile> tilesAt( const NormalizedRect &rect, TileLeaf tileLeaf );

        /**
         * The total memory consumed by the tiles manager
         */
        qulonglong totalMemory() const;

        /**
         * Removes at least @p numberOfBytes bytes worth of tiles (least ranked
         * tiles are removed first).
         * Set @p visibleRect to the visible region of the page. Set a
         * @p visiblePageNumber if the current page is not visible.
         * Visible tiles are not discarded.
         */
        void cleanupPixmapMemory( qulonglong numberOfBytes, const NormalizedRect &visibleRect, int visiblePageNumber );

        /**
         * Checks whether a given region has already been requested
         */
        bool isRequesting( const NormalizedRect &rect, int pageWidth, int pageHeight ) const;

        /**
         * Sets a region to be requested so the tiles manager knows which
         * pixmaps to expect and discard those not useful anymore (late pixmaps)
         */
        void setRequest( const NormalizedRect &rect, int pageWidth, int pageHeight );

        /**
         * Inform the new size of the page and mark all tiles to repaint
         */
        void setSize( int width, int height );

        /**
         * Gets the width of the page in tiles manager
         */
        int width() const;

        /**
         * Gets the height of the page in tiles manager
         */
        int height() const;

        /**
         * Inform the new rotation of the page
         */
        void setRotation( Rotation rotation );
        Rotation rotation() const;

        /**
         * Mark all tiles as dirty
         */
        void markDirty();

        /**
         * Returns a rotated NormalizedRect given a @p rotation
         */
        static NormalizedRect toRotatedRect( const NormalizedRect &rect, Rotation rotation );

        /**
         * Returns a non rotated version of @p rect, which is rotated by @p rotation
         */
        static NormalizedRect fromRotatedRect( const NormalizedRect &rect, Rotation rotation );

    private:
        class Private;
        Private * const d;
        friend class Private;
};

}

#endif // _OKULAR_TILES_MANAGER_P_H_