Re: g_timeout_add events stop when calling draw_brush()

[Douglas Phillipson <dougp intermind net>]

John K Luebs wrote:
> On Sun, Feb 29, 2004 at 03:06:00PM -0800, Douglas Phillipson wrote:
> 
>>Douglas Phillipson wrote:
>>
>>>I'm using  g_timeout_add (500, grab_data, NULL) to aquire data from a 
>>>file and shift it through an array with some procesing on it.  This all 
>>>works fine.  At the end of the routine I call draw_brush to paint the 
>>>data to the screen but the "timeout" event stops after the first call to 
>>>draw_brush.  I can comment out the draw_brush() call and events happen 
>>>as they should.  What might be causing this?
>>
>>A more general question related to the above problem.
>>
>>I'm not drawing. I'm displaying chart like graphic data points.  Without 
>> touching any buttons or the screen, how can I force an update to my 
>>draw_area once a second?  I'm using g_timeout_add to force a read of a 
>>file, all working well.  But I'm trying to throw a expose event on the 
>>draw area from the function called by the "timeout" callback.  It 
>>doesn't seem to force a screen update via draw_brush.  Any suggestions?
>>
> 
> 
> I'm not quite sure I understand what you're trying to do, but you
> shouldn't draw from anywhere outside of handling an expose event. If
> you want to "force" an expose event then use gtk_widget_queue_draw.
> 
> --jkl
> 
> 

I'm taking in information from a file and displaying it on a draw_area. 
  I use g_timeout_add to force the call of my data collection routine. 
This occurs on a regular interval.  I take the data and shift it through 
an array to normalize it to x,y coords that will be within screen 
boundaries.  After each second, I need the screen to update.  In the 
draw_brush code I do the drawing of points from the array.  Again no 
events are occuring other than the input of data from a file.  I presume 
I need to clear the pixmap prior to each draw.  I do this in the 
g_timeout_add callback routine with:

gdk_draw_rectangle (pixmap, widget->style->black_gc, TRUE,
            0, 0, widget->allocation.width, widget->allocation.height);

then proceed to draw the points on the pixmap.  The trouble is I am not 
getting any refresh events to the draw_area in order to copy the pixmap 
to the screen, because I'm not doing anything that triggers a refresh 
event, like drawing with the stylist.  I also have to figure out how to 
get the widget handle for the draw_area to call the gdk_draw_rectangle() 
routine.  I'm in a callback that doesn't have a reference to the handle 
for the draw_area.  If the draw_area handle is global, cat I just use it 
for the "widget->style->black_gc"?

Also, what advantages would a "image" have over a draw_area, if any?

Thanks

DOug P