foreground processes

[Alexander Kotelnikov <sacha AK2614 spb edu>]

Hello, I have a proflem :(

* I have drawing area, that should be changed by iteration process very
frequent (as fast, as it possible) IF toggle button is pressed (or after
button was pressed)

* And I need to stop these changing whenever I want by pressing (toggle or
non-toggle) button one more time.

* But my process catches all of my CPU, and I can't stop. 

Easier:
In my case I have a large bitmap  -- array of chars and iteration
process, that changes it. After each change I need my DrawingArea to be
redraw (drawingarea is just an interface to bitmap). And I need this
process to be stoped when I want.

Thanks in advance,
_____
Alexander Kotelnikov
Saint-Petersburg, Russia
mailto:sacha@ak2614.spb.edu