imagethumbs.h

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#ifndef IMAGETHUMBS_H
#define IMAGETHUMBS_H

#include <QMap>
#include <QMutex>
#include <QWaitCondition>

#include "imagetypes.h"
#include "mthread.h"

enum ImageThumbPriority {
    kUrgentPriority     = -10, 
    kPicRequestPriority =  -7, 
    kDirRequestPriority =  -3, 
    kBackgroundPriority =   0  
};


class META_PUBLIC ThumbTask
{
public:

    ThumbTask(QString action, ImagePtrK im,
              int priority = kUrgentPriority, bool notify = false)
        : m_action(action), m_priority(priority), m_notify(notify)
    { m_images.append(im); }

    ThumbTask(QString action, const ImageListK &list,
              int priority = kUrgentPriority, bool notify = false)
        : m_images(list),
          m_action(action),
          m_priority(priority),
          m_notify(notify)      {}

    ImageListK m_images;
    QString m_action;
    int m_priority;
    bool m_notify;
};

using TaskPtr = QSharedPointer<ThumbTask>;


template <class DBFS>
class ThumbThread : public MThread
{
public:
    ThumbThread(const QString &name, DBFS *const dbfs)
        : MThread(name), m_dbfs(*dbfs) {}
    ~ThumbThread();

    void cancel();
    void Enqueue(const TaskPtr &task);
    void AbortDevice(int devId, const QString &action);
    void PauseBackground(bool pause);

protected:
    void run() override; // MThread

private:
    Q_DISABLE_COPY(ThumbThread)

    
    using ThumbQueue = QMultiMap<int, TaskPtr>;

    QString CreateThumbnail(ImagePtrK im, int thumbPriority);
    static void RemoveTasks(ThumbQueue &queue, int devId);

    DBFS &m_dbfs;               
    QWaitCondition m_taskDone;  

    ThumbQueue m_requestQ;   
    ThumbQueue m_backgroundQ;   
    bool m_doBackground {true}; 
    QMutex m_mutex;            
};


template <class DBFS>
class META_PUBLIC ImageThumb
{
public:
    explicit ImageThumb(DBFS *const dbfs);
    ~ImageThumb();

    void    ClearThumbs(int devId, const QString &action);
    QString DeleteThumbs(const ImageList &images);
    void    CreateThumbnail(const ImagePtrK &im,
                            int priority = kBackgroundPriority,
                            bool notify = false);
    void    MoveThumbnail(const ImagePtrK &im);
    void    PauseBackground(bool pause);

private:
    Q_DISABLE_COPY(ImageThumb)

    
    // Major element = tree depth, so shallow thumbs are created before deep ones
    // Minor element = id, so thumbs are created in order they were scanned
    // If not unique, QMultiMap will process later requests before earlier ones
    int Priority(ImageItemK &im)
    { return im.m_filePath.count('/') * 1000 + im.m_id; }

    DBFS              &m_dbfs;
    ThumbThread<DBFS> *m_imageThread;
    ThumbThread<DBFS> *m_videoThread;
};

#endif // IMAGETHUMBS_H