[pygtk] window.invalidate_rect speed

[Donn]

Nathaniel,
 Thanks for your response. I will try to better explain:

> What do you mean by "out of synch"?  Why is it so urgent that the
> redraw happen quickly?
I mean that *if* the expose event takes too long to run, the loop may have 
begun again and the state of the app will have changed. 
 I am building a 'stack' of objects that represent the state -- what gets 
drawn where and in what order. It goes like this:

This is the loop in my _stack(gtk.DrawingArea) class:
    def _tick(self): 
1.        self.MainTimeline._tick()
2.        _stack._draw()
3.       if _stack.quitApp:
4.            gtk.main_quit()
5.        return True # spawn timeout again.

This function is initially called by:
        gobject.timeout_add(self.speed, self._tick)
        gtk.main()

_stack.draw() is:
    def _draw(self):
        if not self.quitApp:
            self.alloc = self.get_allocation()
            rect = gtk.gdk.Rectangle(self.alloc.x, self.alloc.y, 
self.alloc.width, self.alloc.height)
            self.window.invalidate_rect(rect, True)

So, it forces an expose event in the _stack class that goes through the stack 
and draws all the graphics to the DrawingArea.

> No -- invalidate_rect will generally *not* trigger the expose event
> until after you return to the main loop, i.e., after your _timer
> callback finishes.  
Actually, on my fairly fast machine, the expose event *is* running *and* 
finishing before the return from _tick(). I am worried that this is unplanned 
and that on other machines it may take even longer to run.

So, I need to ensure (somehow) that line 5 (above) does *not* get reached 
until the expose event (triggered by line 2) has finished.
 I can use flags to prevent line 1 from running until expose has finished, but 
I thought I'd try to get a better picture about the timing of these events.

Is there a better, faster, way to force an expose? I don't suppose I can call 
the expose handler directly?

> If you do a busy-loop like this, then not only 
> will you be living in a state of sin (busy-loops are bad!), but you
> will never receive the expose event at all.
As I am actually getting the expose event, I must be doing something right :) 

> What are you trying to do?
I'm writing a retained-mode API to do vector animation using Cairo. 
 So far it's working far better than I had hoped. The user will import my 
module and use the simple API to setup tweens and parent-child relationships.  
 Each object gets a draw() method where the user can use Cairo to draw stuff. 
(I suppose they can use anything they want that will draw in a DrawingArea, 
but I am using Cairo-specific matrixes for controlling everything.

I hope that's clearer!
\d