[Interest] Draw multiple rectangles in a QGraphicsItem using the mouse

[David Carmona]

Hi everybody,

I would like to create a Graphical User Interface which allows the user to
draw as many rectangles as he wants on an image using the left button of
his mouse.
I have already implemented part of the code.
I have a QGraphicsView which displays an image contained in a scene :

bool ImageGraphicsView::display( QString &fileName)
{
    // The image we want to display
    image=new Image(fileName);

    // File instanciation
    file=new CreateFileAbstraction(*image);

    // Save the file in the image directory
    file->createFile();


    rectangle=new ImageGraphicsScene(this,image);

    rectangle->setSceneRect(image->rect());

    item=new ImageGraphicsItem(rectangle->sceneRect(),image,file,this);

    rectangle->addItem(item);

    this->setScene(rectangle);
    this->show();

    mainWindow-> setCentralWidget(this);
    mainWindow->setWindowFilePath(fileName);
    return true;

}

I've added to the scene (ImageGraphicsScene) a QGraphicsItem
(ImageGraphicsItem):

QRectF ImageGraphicsItem::boundingRect()const
{
    QRect p=rect.toRect();
    return QRectF(p);
}

void ImageGraphicsItem::paint(QPainter *painter, const
QStyleOptionGraphicsItem *option, QWidget *widget){

    if(mousePressed){

        painter->drawPixmap(0,0,*pixmap);
        if(selectedTool==1){

            painter->drawRect(y);

            painter->setPen(Qt::blue);
        }

        drawStarted=true;
        painter->setPen(Qt::blue);
    }

    // The rectangle is not erased after the user unpresses the left button
    else if(drawStarted) {

        QPainter *tempPainter=new QPainter(pixmap);
        if(selectedTool==1) {

            tempPainter->drawRect(y);
            tempPainter->setPen(Qt::blue);

        }
        painter->drawPixmap(0,0,*pixmap);
        painter->setPen(Qt::blue);
        tempPainter->setPen(Qt::blue);

    }
    painter->setPen(Qt::blue);
}

void ImageGraphicsItem::mousePressEvent(QGraphicsSceneMouseEvent *event){

    mousePressed=true;
    QPoint e=(event->pos()).toPoint();

    if(selectedTool==1){

        y.setTopLeft(e);
        y.setBottomRight(e);
    }
    this->update();
}

void ImageGraphicsItem::mouseMoveEvent(QGraphicsSceneMouseEvent *event){

    QPoint e=(event->pos()).toPoint();

    if(event->type()==QEvent::GraphicsSceneMouseMove){

        if(selectedTool==1){
            y.setBottomRight(e);

        }
    }

    this->update();

}

void ImageGraphicsItem::mouseReleaseEvent(QGraphicsSceneMouseEvent *event){

    mousePressed=false;
    this->update();
}

With this code, i am able to draw only one rectangle and not several as I
would like.
When I actually try. Qt tells me that QPainter is not active and I can't
draw on the same QPaintDevice at the same time.

Thank you so much for your help
David
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