chartscene.h

#ifndef CHARTSCENE_H
#define CHARTSCENE_H

#include <QDomDocument>
#include <QGraphicsScene>
#include <QGraphicsSceneWheelEvent>
#include <QLinkedList>

//Specialised QGraphicsScene, with background grid,
//...and BlockItem management functions.
class ChartScene : public QGraphicsScene {
    Q_OBJECT
public:
    using QGraphicsScene::QGraphicsScene;
//Adds 'filename' to be searched for BlockItem types.
    //Displays a dialog if no filename provided.
    bool addBlockFile(QString filename = 0);
//List of BlockItem types known by this scene.
    QStringList blockTypes() const;
//Spacing between grid lines, in pixels.
    int gridSize() const { return grid_size; }
    void setGridSize(int new_size) { grid_size = new_size; }
public slots:
//Adds a BlockItem of type 'block_type' to the scene at (0, 0).
    //Returns 1 on success or 0 otherwise.
    bool addBlockItem(const QString& block_type);
protected:
//Paints a grid on the background, spacing from 'grid_size'.
    virtual void drawBackground(QPainter* painter, const QRectF& rect);
//Handles Key_Delete to remove items.
    virtual void keyPressEvent(QKeyEvent* event);
//Sends wheel events to the mouse grabber if one exists.
    virtual void wheelEvent(QGraphicsSceneWheelEvent* event);
private:
//Spacing of background grid.
    int grid_size = 20;
//List of XML documents containing BlockItem types.
    QLinkedList<QDomDocument> block_documents;
};

#endif //CHARTSCENE_H