CODEWITHSUNDEEP
qtmouseeventqpainter
sh ze
sh ze

Reputation: 169

Drawing a point in the exact position of a mouse click using Qt

I'm working on a Qt project. A point must be drawn on a mouse click on a Qpainter area. The point position is supposed to be on the same exact position of the mouse click, but for some reason the point is drawn in another position diagonal to the expected position.

The code :

MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent), ui(new Ui::MainWindow)
{
QGraphicsView * view = new QGraphicsView(this) ;
ui->setupUi(this);
QGridLayout * gridLayout = new QGridLayout(ui->centralWidget);
gridLayout->addWidget(view);

scene = new QGraphicsScene();
scene->setSceneRect(50, 50, 350, 350);

view->setScene(scene);
} 

void MainWindow::mousePressEvent(QMouseEvent * e)
{
 QGraphicsView * view = new QGraphicsView(this) ;
 double rad = 1;
 QPointF pt = view->mapToScene(e->pos());
 scene->addEllipse(pt.x()-rad, pt.y()-rad, rad*2.0, rad*2.0,QPen(),  QBrush(Qt::SolidPattern));
}

Upvotes: 1

Views: 2855

Answers (1)

Jablonski
Jablonski

Reputation: 18524

Your code is not correct. You create heavy view every clicking, you should not do this. If you want that user will be able to interact with scene, then create new custom scene and do all hat you need in scene.

#ifndef GRAPHICSSCENE_H
#define GRAPHICSSCENE_H

#include <QGraphicsScene>
#include <QPoint>
#include <QMouseEvent>
class GraphicsScene : public QGraphicsScene
{
    Q_OBJECT
public:
    explicit GraphicsScene(QObject *parent = 0);
    ~GraphicsScene();

signals:

protected:
    void mousePressEvent(QGraphicsSceneMouseEvent *event);
public slots:
    private:

};

#endif // GRAPHICSSCENE_H

cpp:

#include "graphicsscene.h"
#include <QDebug>

GraphicsScene::GraphicsScene(QObject *parent) :
    QGraphicsScene(parent)
{
}

GraphicsScene::~GraphicsScene()
{
    qDebug() << "deleted scene";
}


void GraphicsScene::mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent)
{

      if (mouseEvent->button() == Qt::LeftButton)
      {
          double rad = 1;
          QPointF pt = mouseEvent->scenePos();
          this->addEllipse(pt.x()-rad, pt.y()-rad, rad*2.0, rad*2.0,QPen(),
          QBrush(Qt::SolidPattern));
      }

    QGraphicsScene::mousePressEvent(mouseEvent);
}

Usage, for example:

#include "graphicsscene.h"
//...
GraphicsScene *scene = new GraphicsScene(this);
someview->setScene(scene);

Upvotes: 2

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