Artificial MouseEvent and natural MouseEvent on QGraphicsView return different positions

  • Dear All,

    Since I am kind of a Qt-novice I apologize if this has been asked/cleared before but my forum search didn't yield any results that could solve my problem.

    I am trying to create a drawing app where the user can enter basic shapes like points and polygons. The app contains a menubar on the left which is a QWidget with some nested layout. On the right I created a QWidget which contains a subclassed QGraphicsView called inputViewer and some labels below, arranged in a layout aswell. The scenes that are displayed in the inputViewer are subclasses of QGraphicsScene called inputModel.

    To handle the drawing, I overwrote the mousePressEvent-functions on both, the QGraphicsView and the QGraphicsScene. The actual drawing by mouse where only the mousePressEvent-functions get called work as I would expect it and therefore I assume these are correct.

    I want the user to be able to also draw a point at the cursor-position when the Qt::Key_Return is pressed. For that I overwrote the inputViewer::keyPressEvent() and artificially triggered a QMousePressEvent. For the position of the QMousePressEvent I created a QCursor object in the inputViewer and get the position by calling cursor->pos() (returns global coordinates afaik) and map them to the inputViewer with mapFromGlobal(). The inputViewer::mousePressEvent() is not overwritten and therefore should propagate the event right down to the scene if I am not mistaken.

    The problem is that if I let the program output the coordinates that I get from points being drawn by mouse and points being drawn by keyboard, there is a little offset. For example if I click on my canvas, don't move the mouse and press Return the output of the program is not the same.

    I hope the example is sufficient and thank all of you for your help and patience in advance.



    The program:

    void inputViewer::keyPressEvent(QKeyEvent *event)
    ... some other if and elses to handle different keys ...
    else if(event->key() == Qt::Key_Return)
    QMouseEvent event =QMouseEvent(QEvent::MouseButtonPress,this->mapFromGlobal(cursor->pos()),Qt::LeftButton,Qt::LeftButton,Qt::NoModifier);

    void inputModel::mousePressEvent(QGraphicsSceneMouseEvent *event)
    std::cout << " Scene-coordinates are: " << event->scenePos().x() << " " << event->scenePos().y() << std::endl;
    ... some drawing functions like adding an ellipse ...

  • Qt Champions 2016

    Hi I dont know about mouse coors
    but Just wanted to make sure you saw
    Diagram Scene Example
    in case you could borrow stuff from that.

Looks like your connection to Qt Forum was lost, please wait while we try to reconnect.