Updating Foreground for QGraphicsView

[Gopala Krishna]

Only problem is that only a bounding rect region containing all graphics items in the scene is updated. Is that where the rubber band technique comes in? At the moment I simply call QGraphicsScene->update(QGraphicsScene->sceneRect()) which updates the entire scene. Not very efficient way to do things I suppose.
Thuan Seah

You can use QRubberBand with its parent being QGraphicsView->viewport() and then call setGeometry() appropriately while providing feedback of line being drawn. You need not update scene in that case. See QRubberBand's doc for more details.

[aamer4yu]

well if u are implementing the edge as item, u need not worry about the rubber banding. what u need to do is just change the shape of the item on mouse movements.
for this u can maintain a list of edges in contact with a node, now when the node moves, u change the shape of edges connected to it and call the update to items if necessary.
As for the bounding rect u can return the rectangle covered by the line.
for shape, override the shape() method... and be sure to call prepareGeometryChange() before changing the shape...

try it, hope it will solve the prob

[Gopala Krishna]

Just one more tip for you. I guess you can use already existing QGraphicsLineItem or a class derived from it for edges which simplies a lot. You just need to call QGraphicsLineItem::setLine(QLineF line) method and no need to worry about geometry at all. Hope this helps.