Diagram Scene Example ::paint and ::setPolygon

[markwang]

as the example Diagram Scene Example:
diagramitem.cpp

        setPolygon(myPolygon);
        setFlag(QGraphicsItem::ItemIsMovable, true);
        setFlag(QGraphicsItem::ItemIsSelectable, true);
        setFlag(QGraphicsItem::ItemSendsGeometryChanges, true);

item can select, move;
but when i change it a little:
to：

//setPolygon(myPolygon);
           setFlag(QGraphicsItem::ItemIsMovable, true);
           setFlag(QGraphicsItem::ItemIsSelectable, true);
           setFlag(QGraphicsItem::ItemSendsGeometryChanges, true);

QRectF  DiagramItem::boundingRect() const
{
    qreal penWidth = 1;
    switch (myDiagramType) {
        case StartEnd:
            return QRectF(0 - penWidth / 2,0 - penWidth / 2,
               200 + penWidth, 200 + penWidth);
            break;
        case Conditional:
            return QRectF(-100 - penWidth / 2, -100 - penWidth / 2,
                           200 + penWidth, 200 + penWidth);
        case Step:
            return QRectF(-100 - penWidth / 2, -100 - penWidth / 2,
                       200 + penWidth, 200 + penWidth);
        case Io:
            return QRectF(-120 - penWidth / 2, -80 - penWidth / 2,
                   240 + penWidth, 160 + penWidth);
    }

}

void  DiagramItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget )
{
    painter->drawPolygon(myPolygon );
}

item can show but can be selected and moved, Arrow can not work also;

[markwang]

[markwang]

Reimplement mouseMoveEvent and mousePressEvent; set breakPiont . finded that it is not executed.

[markwang]

This post is deleted!

[markwang]

ha, diagramitem Inherit QGraphicsPolygonItem ， change it to inherit QGraphicsItem.