force drawing area expose on button click

[Scott Rubin <slr2777 cs rit edu>]

Hi,

I'm working on a project for a class and I'm using gtkglext and 
gtk+-2.0.  I was previously doing the program in glut, but I needed to 
add gui elements.  Mostly this project has been a huge success, and I am 
very pleased with the results.  However, I have come across one problem.

Presently I have it coded so the map and unmap events are linked to 
callbacks in such a way that during the idle state the following are 
called repeatedly.

gdk_window_invalidate_rect (widget->window, &widget->allocation, FALSE);

gdk_window_process_updates (widget->window, FALSE);

This works great, but it uses 100% of the cpu.  Since my program has no 
animation there is really no need to redraw the area all the time.

My gui has a large number of buttons and keyboard inputs and such.  What 
I would like to do is force the drawing area to expose whenever the user 
clicks a button or presses a key on the keyboard.  Of course the 
redrawing should occur after the button's usual function. 

My problem is that if I do something like this:

g_signal_connect_after( G_OBJECT (button), "clicked", G_CALLBACK (redraw), NULL );

Then the widget argument to the redraw callback function will be button 
and not drawing_area.  In order to call invalidate_rect and 
process_updates I need to access the drawing_area, which seems to only 
be possible if the signal is connected to the drawing area itself.  I 
also tried passing pointers to the drawing_area in the data field, but I 
think I may have done it wrong. 

To put it simply.  How can I force the expose event to happen on the 
drawing_area widget whenever a clicked event is signaled on one of my 
button widgets.  Thanks.

-Scott