What's wrong with QGraphicsItem::childItems?
I am not there yet, this will be the next version.
In the current version, the only QGraphicsitems are the fields, and the content is drawn by painter calls.
Hard to say without seeing the code. If you modify the scene after the view is shown for the first time or you use fitInView, then it might happen that the view is drawn twice.
This is what I do. Could you suggest an alternative way, without this effect?
Hmm? Why? If you zoom in, the field and its subfields are visible so only they will be drawn. You store subfields as child items of a field, right?
No, not in this version. See above.
If you draw the polygon using a painter path then lines are faster. If you draw the polygon and not polyline then definitely lines are faster. But using QPainter::drawPolyLine() will call drawLines() internally, so the overhead is minimal. If you draw lines, use QPainter::drawLines() instead of multiple calls to QPainter::drawLine().
Thanks for this, I will use it.
Any (performance-wise) preferred way to draw filled surfaces?