plugin_view.h

#pragma once
 
#include <QGraphicsView>
#include <QKeyEvent>
#include <QWheelEvent>

class PluginView : public QGraphicsView
{
  Q_OBJECT
 
public:
  PluginView(QWidget* parent = nullptr);

  QPointF getCenter() const;

  qreal getScale() const;

  void setScale(qreal scale);

  void zoom(float scaleFactor);

  void centerOn(const QPointF& pos);

  void centerOn(const QGraphicsItem* item);
 
protected:
  void keyPressEvent(QKeyEvent*) override;

  void keyReleaseEvent(QKeyEvent*) override;

  void mouseMoveEvent(QMouseEvent*) override;

  void mousePressEvent(QMouseEvent*) override;

  void mouseReleaseEvent(QMouseEvent*) override;

  void wheelEvent(QWheelEvent*) override;
 
private:
  bool mDoMousePanning;  

  bool mDoKeyZoom;  

  QPoint mLastMousePos;  

  QPointF mCenterPoint;  

  qreal mPanSpeed;  

  qreal mZoomDelta;  

  Qt::Key mZoomKey;  

  qreal mMinZoom;  

  qreal mMaxZoom;  

  Qt::MouseButton mPanButton;  

  void pan(QPointF delta);

  void zoomIn();

  void zoomOut();

  void resetZoom();

  qreal quantisedScale(qreal proposedScale) const;

  void setMaxSize();
};