Does this ring a bell by anyone ?

[Stef Mientki]

hello,

I'm writing (another) plot library for real-time plotting.
On resize of the plotcanvas, I recalculate and redraw the image.
The redrawing of the image is done in the following steps:
- draw a grid of 10*10, using DrawRectangleList (because it's less code)
- draw the signals

A very few times this works ok,
but in general I only get to see the grid, but no signals.

The signals are there, but they are not shown.
I know that they are there, because if I move another window over it,
the part that was covered by the other window,
shows the signals.

I tried to add an OnPaint action after the drawing is made, but that 
isn't allowed ?

Any hints, solutions ?

thanks,
Stef Mientki