how to implement delayed calculation of node/shape

[Zsolt Kúti]

Hi,
Some of my classes extend Path or Group and constructed by non-trivial
algorithms that may use many properties, either standard (like strokeWidth)
or non-standard ones. Setting a property calculates a new state at present.
When several properties are set it means a lot of unnecessary calculations
done.

I would like to delay geometry/shape calculations similar the way
Node/Shape do. They signal their state changes by dirty flagging and on
pulse necessary synchronization does recalculations when being dirty.
However relevant methods despite being public are deprecated (tipically
ones starting with impl_) and cannot be relied upon.

Is there a way to achive that kind of design for own classes?
Thx!

Zsolt