How to display mouse coordinates in QGraphicsView

[edujar]

Hello,

How can I display the mouse coordinate position (XY) on my derived QGraphicsView class.

I get the coordinates on mouseMoveEvent and even I can make a string with them, but I do not how to display the string and get it changed when the mouse moves.

Thanks
ejar

[Santosh Reddy]

QGraphicsView is used to view the items which are in a QGraphicsScene. If you need to see the cursor position updating in the view, you need to something like this.

Add a QGraphicsTextItem in your custom QGraphicsScene, and then update the the text of the item in QGraphicsScene::mouseMoveEvent()

MyGraphicsScene::MyGraphicsScene(QObject* parent)
    : QGraphicsScene(parent)
{
    cursor = new QGraphicsTextItem("0, 0", 0, this); //Fixed at 0, 0
}
 
void MyGraphicsScene::mouseMoveEvent(QGraphicsSceneMouseEvent* event)
{
    QString string = QString("%1, %2")
                        .arg(event->scenePos().x())
                        .arg(event->scenePos().y()); //Update the cursor potion text
 
    cursor->setPlainText(string);
}

MyGraphicsScene::MyGraphicsScene(QObject* parent)
    : QGraphicsScene(parent)
{
    cursor = new QGraphicsTextItem("0, 0", 0, this); //Fixed at 0, 0
}

void MyGraphicsScene::mouseMoveEvent(QGraphicsSceneMouseEvent* event)
{
    QString string = QString("%1, %2")
                        .arg(event->scenePos().x())
                        .arg(event->scenePos().y()); //Update the cursor potion text

    cursor->setPlainText(string);
}

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I am not sure, if this what you are trying to do, looks like your are creating a custom QGraphicsView.

[edujar]

Hi Santosh and thanks for your fast response.

Yes, I think I am creating a custom QGraphicsView. I have got an intermediate solution to my question with the code you have sent, but the ideal would be to draw the text directly on my derived class from QGraphicsView.
Let´s say that I want to display the mouse XY position always on the right bottom corner of the QGraphicsView. Doing on that way, it doesn´t matter about any scroll or zooming factor. Otherway I have to recalculate the position where to display the coordinates for each change on the view.

My application is a GIS one, where I need to know the Latitude and Longitude of the cursor on the scene and display it at the right bottom corner of the view.

Thanks
ejar

[Santosh Reddy]

As far as I understand you can only add items to a scene not to view, so you need to get the current view's view port and then add the cursor there, this needs to be in your scene, something like this

void MyGraphicsScene::mouseMoveEvent(QGraphicsSceneMouseEvent* event)
{
    // Get the list of the views attached to this scene
    QList<QGraphicsView*> scene_views = views();
 
    for(int i = 0; i < scene_views.count(); i++)
    {
        // get the visible view port
        QWidget* viewport_widget = scene_views.at(i)->viewport();
 
        // ensure it is visible
        if(viewport_widget->isVisible())
        {
            // Update cursor position (text to be displayed)
            QString string = QString("%1, %2")
                                .arg(event->scenePos().x())
                                .arg(event->scenePos().y());
 
            cursor->setPlainText(string);
 
            // Set the new position of the cursor
            cursor->setPos(viewport_widget->width() - cursor->boundingRect().width()
                           ,viewport_widget->height() - cursor->boundingRect().height());
        }
    }
}

void MyGraphicsScene::mouseMoveEvent(QGraphicsSceneMouseEvent* event)
{
    // Get the list of the views attached to this scene
    QList<QGraphicsView*> scene_views = views();

    for(int i = 0; i < scene_views.count(); i++)
    {
        // get the visible view port
        QWidget* viewport_widget = scene_views.at(i)->viewport();

        // ensure it is visible
        if(viewport_widget->isVisible())
        {
            // Update cursor position (text to be displayed)
            QString string = QString("%1, %2")
                                .arg(event->scenePos().x())
                                .arg(event->scenePos().y());

            cursor->setPlainText(string);

            // Set the new position of the cursor
            cursor->setPos(viewport_widget->width() - cursor->boundingRect().width()
                           ,viewport_widget->height() - cursor->boundingRect().height());
        }
    }
}

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[edujar]

Thanks again. The code above has the limitation of working with QGraphicsScene. Scene is fine becasue I have some graphics to display and it provides a very useful way, but it doesn´t for my mouse coordinates.
Going back to the coordinate, is there a way to use something like QPainter::drawText and use it on the view. Is should be able to call the function each time the mouse moves.

Ejar

[WE-B-QT-N]

Hello I realize this is a old thread. Very interesting, I have questions on the cord system also...i would like to try this code but dont know quite how to do it. If you are still a member could you elaborate more?