Highlight QGraphicsItem during connection.

[salcin]

Hi,

I'm playing around with the Diagramscene example provided with QT. What I would like to accomplish is to highlight the DiagramItem when connecting two boxes (e.g. process box).

I have tried to implement the hoverEnter/hoverLeave event and it seems to work for the box I start the connect. When I enter the other box while dragging a line no events are passed to the other DiagramItem. When I release the mousebutton I get hoverEnter events.

How can I make this work?

[wysota]

It depends how you implemented what you have so far.

[salcin]

I started with Diagramscene example.
In DiagramItem.cpp/.h I override:

void DiagramItem::hoverEnterEvent(QGraphicsSceneHoverEvent * event)
{
    qDebug() << (int)this << ": Hover enter event";
    m_color = Qt::cyan;
    QGraphicsPolygonItem::hoverEnterEvent(event);
}
 
void DiagramItem::hoverLeaveEvent(QGraphicsSceneHoverEvent * event)
{
    qDebug() << (int)this << ": Hover leave event";
    m_color = Qt::black;
    QGraphicsPolygonItem::hoverLeaveEvent(event);
}
 
void DiagramItem::paint(QPainter * painter, const QStyleOptionGraphicsItem * option,
                        QWidget * widget)
{
    if (option->state & QStyle::State_MouseOver )
    {
        qDebug() << (int)this << "Mouse over!";
    }
 
    QPen p = pen();
    p.setColor(m_color);
    setPen(p);
    qDebug() << m_color;
    QGraphicsPolygonItem::paint(painter, option, widget);
}

void DiagramItem::hoverEnterEvent(QGraphicsSceneHoverEvent * event)
{
    qDebug() << (int)this << ": Hover enter event";
    m_color = Qt::cyan;
    QGraphicsPolygonItem::hoverEnterEvent(event);
}

void DiagramItem::hoverLeaveEvent(QGraphicsSceneHoverEvent * event)
{
    qDebug() << (int)this << ": Hover leave event";
    m_color = Qt::black;
    QGraphicsPolygonItem::hoverLeaveEvent(event);
}

void DiagramItem::paint(QPainter * painter, const QStyleOptionGraphicsItem * option,
                        QWidget * widget)
{
    if (option->state & QStyle::State_MouseOver )
    {
        qDebug() << (int)this << "Mouse over!";
    }

    QPen p = pen();
    p.setColor(m_color);
    setPen(p);
    qDebug() << m_color;
    QGraphicsPolygonItem::paint(painter, option, widget);
}

To copy to clipboard, switch view to plain text mode 

in void DiagramScene::mousePressEvent(QGraphicsSceneMouseE vent *mouseEvent) I added item->setAcceptHoverEvents(true);

[salcin]

Ok, I solved it.
Instead of putting code in hoverenter/hoverleave of the DiagramItem, I put the code in scene's mouseMoveEvent. To know wich item to highlight I reused some of the code in mouseReleseEvent.