QGraphicsItem::update(); vs scene()->update();

[Lord_Navro]

Hi,

I'm trying to make an editor based on the diagramscene example (http://qt-project.org/doc/qt-4.8/gra...gramscene.html). I have a very similar arrow-updating technique as shown in the tutorial. However, I encountered problems while trying to update the arrow shape when the source/target item geometry changes. Here is the function that gets called

void ArcItem::geometryChanged()
{
    computePath();
    computePolygon();
    computeShape();
    update();
}

void ArcItem::geometryChanged()
{
    computePath();
    computePolygon();
    computeShape();
    update();
}

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The arrow has a bit more complex shape which gets recomputed in the first three functions based on new positions. However, eventhough update() is called (and shape() is not isEmpty(), which I checked), sometimes, when moving the target graphicsItem arround for a while, the paint() method gets not called and the arrow simply disappears and then after some more dragging appears again. I failed to determine circumstances of these strange events and the only way I found to mage the arrows repaint correctly was to call scene()->update() which compromises performance greatly. The whole project is here https://github.com/LordNavro/CPNSimulator, the arrow graphics item is here https://github.com/LordNavro/CPNSimu...er/arcitem.cpp ...

Thanx for any suggestions.

[wysota]

QGraphicsItem::prepareGeometryChange()