D1: Repainting the whole form, not just the clippedRectangle

How can I force Windows to repaint the whole of a window, not just the
clippedrectangle when OnPaint is called.

TI am passing the Canvas as a parameter to a class that handles the
drawing (and draws the whole picture).  The problem ocurs when only part
of the Form is hidden.  When OnPaint is called it paints a scaled down
version of the whole picure over the bit of the window that was hidden.

Any help gratefully appreciated.

Olly Morgan
Scottish Agricultural College
Edinburgh, Scotland

email: O.Mor...@ed.ac.uk  (remove the -z from the address)