imagescaling.h Example File

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 #ifndef IMAGESCALING_H
 #define IMAGESCALING_H

 #include <QtWidgets>
 #include <QtConcurrent>

 #ifndef QT_NO_CONCURRENT

 class Images : public QWidget
 {
 Q_OBJECT
 public:
     Images(QWidget *parent = 0);
     ~Images();
 public Q_SLOTS:
     void open();
     void showImage(int num);
     void finished();
 private:
     QPushButton *openButton;
     QPushButton *cancelButton;
     QPushButton *pauseButton;
     QVBoxLayout *mainLayout;
     QList<QLabel *> labels;
     QGridLayout *imagesLayout;
     QFutureWatcher<QImage> *imageScaling;
 };

 #else

 // Dummy class required because QT_NO_CONCURRENT is not set when moc is run.
 class Images : public QWidget
 {
 Q_OBJECT
 public Q_SLOTS:
     void open() {}
     void showImage(int) {}
     void finished() {}
 };

 #endif // QT_NO_CONCURRENT

 #endif // IMAGESCALING_H