ROOT's "how to Draw objects" + source code answer this question:
user has to provide UsersObject::Draw method which doesn't draw
anything and UsersObject::Paint method which does drawing by
using TPad::DrawPrimitive
(Primitive here stands for Line, Polyline etc). An code example
would be extremely helpful here, because in all the tutorials
only Draw method is used... (I have to admit that "Draw" is far
from being the best name for the function which appends a pointer
to one object to another one)
BTW, we have a potential problem here.
If the same object is displayed in 2 windows (for example, default
and zoomed views) user has to care about having 2 different copies
of the same object - otherwise the same pointer will be deleted
twice when both windows are closed...
This problem could be solved by introducing a class (say, TPointer)
describing a smart pointer which would
know whether it has actually been allocated and therefore should be
deleted by the destructor or it just clones already allocated pointer
so delete operator should not be called for it?
May be a class providing this functionality already exists but has
a name which doesn't tell it?
Regards, Pasha.