Create a square in a scene with RubberBandDrag

[AlvaroS]

Hello to everyone.

First of all thanks a lot for reading this post and being able to help.

I have an Scene where I would like to add a square item (polygon) just with RubberBandDrag mode.

So user clicks on scene and drag mouse and when users releases mouse then add the polygon.

How can I do that? thanks.

[mrjj]

Hi
no sample for rubberband. sadly

Maybe this is interesting?
http://www.walletfox.com/course/qgraphicsitemruntimedrawing.php

[Devopia53]

@AlvaroS

Hi.

I have an Scene where I would like to add a square item (polygon) just with RubberBandDrag mode.
So user clicks on scene and drag mouse and when users releases mouse then add the polygon

something like this:

drawRect = QRectF(0, 0, 0, 0);
connect(ui->graphicsView, &QGraphicsView::rubberBandChanged,
        [&](QRect rubberBandRect, QPointF fromScenePoint, QPointF toScenePoint){
    if (rubberBandRect.isNull()) {
        ui->graphicsView->scene()->addRect(drawRect);
        drawRect = QRectF(0, 0, 0, 0);            
    }
    else
        drawRect = QRectF(fromScenePoint, toScenePoint);
});

[AlvaroS]

@Devopia53 Thanks a lot my friend. It works.

Now, how can i disconnect it??
Because I would like to connect it when I press a button and when I press the same button again to disconnect it.

Thanks again!

[AlvaroS]

@Devopia53 said:

@AlvaroS

Hi.

I have an Scene where I would like to add a square item (polygon) just with RubberBandDrag mode.
So user clicks on scene and drag mouse and when users releases mouse then add the polygon

something like this:

drawRect = QRectF(0, 0, 0, 0);
connect(ui->graphicsView, &QGraphicsView::rubberBandChanged,
        [&](QRect rubberBandRect, QPointF fromScenePoint, QPointF toScenePoint){
    if (rubberBandRect.isNull()) {
        ui->graphicsView->scene()->addRect(drawRect);
        drawRect = QRectF(0, 0, 0, 0);            
    }
    else
        drawRect = QRectF(fromScenePoint, toScenePoint);
});

@mrjj said:

Hi
no sample for rubberband. sadly

Maybe this is interesting?
http://www.walletfox.com/course/qgraphicsitemruntimedrawing.php

Hello again. i have just figured it out the solution and it is the next:

    if (check_generate_boxes_button == 0){
        ui->graphicsView->blockSignals(false);
        connect(ui->graphicsView, &QGraphicsView::rubberBandChanged,
                [&](QRect rubberBandRect, QPointF fromScenePoint, QPointF toScenePoint){
            if (rubberBandRect.isNull()) {
                rectangle = ui->graphicsView->scene()->addRect(drawRect);
                std::cout << "estoy en if" << std::endl;
                drawRect = QRectF(0, 0, 0, 0);
                rectangle->setFlag(QGraphicsRectItem::ItemIsSelectable, true);
                rectangle->setCursor(Qt::PointingHandCursor);
            }
            else{
                drawRect = QRectF(fromScenePoint, toScenePoint);
                std::cout << "estoy en ELSE DEL if" << std::endl;
            }

        });
        check_generate_boxes_button = 1;
    }

    else{
        ui->graphicsView->blockSignals(true);
        check_generate_boxes_button = 0;
    }

I would like that the rectangle is selectable. It does not give me an error but when I select the rectangle that I define the program is unexpectedly finish.

Does anyone know why?

thanks!!!

[euchkatzl]

A Stack Trace would help.

What are you doing with your rectangle variable ?
Is it deleted anywhere ?