[wxBufferedPaintDC] Stacking DCs across multiple windows causes bad redraw

[Mario Figueiredo]

Hello everyone,

If I have one onPaint event drawing on a window through
wxBufferedPaintDC and from there directly, or indirectly, I end up
calling another window OnPaint event which also uses a
wxBufferedPaintDC, the first window doesn't get properly updated.

I can enter into more details about it on how I'm experiencing this
behavior, but if it is not necessary, consider two windows sitting
inside the same container. One of the windows OnPaint() explicitly
calls the other window OnPaint() or does so indirectly, for instance
by changing a data member of that window that triggers a custom event
processed by OnPaint().

I'm unsure at this point - and I can't be at the moment I'm writing
this - that wxPaintDC displays similar behavior. But I reckon it does.

I would like to understand why this happens and if there is some way I
can safely stack DCs usage across multiple windows.