[Sugar-devel] Is there a way to purposefully do synchronous GUI updates?

[Benjamin Berg]

On Tue, 2012-08-21 at 12:18 +0530, Ajay Garg wrote:
> I am wanting to solve an issue, which in the present case seems
> possible ONLY by using two threads.

Adding threads into the mix would not help you with your issue
(threading support in GTK+ is currently being deprecated for good
reasons, so then you can only do GTK+ calls from the main thread).

In the normal case, when the GUI is updated a queue_draw() is done. The
corresponding expose events are only fired when the main loop is
executed, ie. when your function returns.

I think what you are searching for right now is the the process_updates
function of GdkWindow. This does exactly what you are requesting. Please
note that you don't have much control here, you don't know how fast the
update will happen, or even if it is ever visible to the user. The X
server will process the drawing commands when it sees fit.

> My intention is to somehow have GUI updates in a synchronous manner,
> and not rely upon "gobject.idle_add", which would have to have
> dividing a long workflow into many sub-parts, and chaining these
> sub-parts through "gobject.idle_add".
> This is EXTREMELY painful, especially when one needs to do it on an
> already existing codebase.

As an alternative you could do something like:

def idle_add_function(pos):
    if pos[0] == 1:
        # logic 1
    elif pos[0] == 2:
        # logic 2
    else:
        return False

    queue_update()

    pos[0] += 1
    return True
    
Where pos = [0] to begin with (the usage of the list is just so that it
is global in a way, any object will do, it just needs to be something
permuteable).

Benjamin