/* ============================================================
 *
 * This file is a part of digiKam project
 * http://www.digikam.org
 *
 * Date        : 2006-04-14
 * Description : Load and cache tag thumbnails
 *
 * Copyright (C) 2006-2007 by Marcel Wiesweg <marcel.wiesweg@gmx.de>
 *
 * 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, or (at your option)
 * any later version.
 * 
 * This program 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 General Public License for more details.
 *
 * ============================================================ */

#ifndef TAGTHUMBNAILLOADER_H
#define TAGTHUMBNAILLOADER_H

// TQt includes.

#include <tqobject.h>
#include <tqpixmap.h>

// KDE includes.

#include <kurl.h>

class TQCustomEvent;

namespace Digikam
{

class Album;
class TAlbum;
class PAlbum;
class AlbumThumbnailLoaderPrivate;

class AlbumThumbnailLoader : public TQObject
{
    Q_OBJECT

public:

    static AlbumThumbnailLoader *instance();
    static void cleanUp();

    /**
     * Change the size of the thumbnails.
     * If the size differs from the current size,
     * signalReloadThumbnails will be emitted.
     */
    void setThumbnailSize(int size);
    /**
     * Get the current default icon size
     */
    int  thumbnailSize() const;

    /**
     * Album thumbnail size is configurable via the settings menu.
     * Some widgets use smaller icons than other widgets.
     * These widgets do not need to know the currently set icon size from
     * the setup and calculate a smaller size, but can simply request
     * a relatively smaller icon.
     * Depending on the user-chosen icon size, this size may in fact not
     * be smaller than the normal size.
     */
    enum RelativeSize
    {
        NormalSize,
        SmallerSize
    };

    /**
     * Request thumbnail for given album.
     * The thumbnail will be loaded
     * and returned asynchronously by the signals.
     * If no thumbnail is associated with given album,
     * no action will be taken, and false is returned.
     * 
    */
    bool getAlbumThumbnail(PAlbum *album);

    /**
      * Behaves similar to the above method.
      * Tag thumbnails will be processed as appropriate.
      * Tags may have associated an icon that is loaded
      * synchronously by the system icon loader.
      * In this case, icon is set to this icon, and false is returned.
      * If no icon is associated with the tag, icon is set to null,
      * and false is returned.
      * If a custom icon is associated with the tag,
      * it is loaded asynchronously, icon is set to null,
      * and true is returned.
      * Tag thumbnails are always smaller than album thumbnails -
      * as small as an album thumbnail with SmallerSize.
      * They are supposed to be blended into the standard tag icon
      * obtained below, or used as is when SmallerSize is requested anyway.
      * @return Returns true if icon is loaded asynchronously.
      */
    bool getTagThumbnail(TAlbum *album, TQPixmap &icon);

    /**
     * Return standard tag and album icons.
     * The third methods check if album is the root,
     * and returns the standard icon or the root standard icon.
     */
    TQPixmap getStandardTagIcon(RelativeSize size = NormalSize);
    TQPixmap getStandardTagRootIcon(RelativeSize size = NormalSize);
    TQPixmap getStandardTagIcon(TAlbum *album, RelativeSize size = NormalSize);

    TQPixmap getStandardAlbumIcon(RelativeSize size = NormalSize);
    TQPixmap getStandardAlbumRootIcon(RelativeSize size = NormalSize);
    TQPixmap getStandardAlbumIcon(PAlbum *album, RelativeSize size = NormalSize);

    /**
     * Blend tagIcon centered on dstIcon, where dstIcon is a standard
     * icon of variable size and tagIcon is 12 pixels smaller.
     * If height(dstIcon) < minBlendSize we return tagIcon verbatim.
     */
    TQPixmap blendIcons(TQPixmap dstIcon, const TQPixmap &tagIcon);


signals:

    /**
     * This signal is emitted as soon as a thumbnail has become available
     * for given album.
     * This class is a singleton, so any object connected to this
     * signal might not actually have requested a thumbnail for given url
     */
    void signalThumbnail(Album *album, const TQPixmap&);

    /** This signal is emitted if thumbnail generation for given album failed.
     *  Same considerations as above.
     */
    void signalFailed(Album *album);

    /**
     * Indicates that all album and tag thumbnails need to be reloaded.
     * This is usually because the icon size has changed in the setup.
     */
    void signalReloadThumbnails();

protected slots:

    void slotGotThumbnailFromIcon(const KURL&, const TQPixmap&);
    void slotThumbnailLost(const KURL&);
    void slotIconChanged(Album* album);

protected:

    void customEvent(TQCustomEvent *e);

private:

    AlbumThumbnailLoader();
    ~AlbumThumbnailLoader();
    AlbumThumbnailLoaderPrivate *d;
    static AlbumThumbnailLoader *m_instance;

    void addURL(Album *album, const KURL &url);
    TQPixmap loadIcon(const TQString &name, int size = 0);
    TQPixmap createTagThumbnail(const TQPixmap &albumThumbnail);
    int computeIconSize(RelativeSize size);
    TQRect computeBlendRect(int iconSize);
};

} // namespace Digikam

#endif // TAGTHUMBNAILLOADER_H