Re: GtkProgressBar ignoring gtk_widget_queue_draw()

[Owen Taylor <otaylor redhat com>]

Richard Stellingwerff wrote:
> Hi,
>
> I am new to this list, so please bear with me :)
>
> Currently I'm working on a gtk engine called Clearlooks. Based on a
> nice idea from jimmac, I tried to implement an animated progressbar.
>
> Unfortunately, it seems that no matter how often I call
> gtk_widget_queue_draw() on a GtkProgressBar, it will not get redrawn.
> Apparently there's some double-double buffering going on or something.
> I added printf() to the draw_box method, but it never gets drawn on a
> GtkProgressBar's expose event. It only gets called after a resize
> event. So somewhere the contents are kept offscreen and then just
> blitted onto the screen. This is not the case for other widgets like
> buttons. An expose event will cause a redraw event.

The great thing about an open source toolkit is that you don't
have to speculate, you can just go and look.

> I am not sure why GtkProgressBar is different in this regard. 

History probably ... prior to GTK+-2.0, a widget that was animating
like GtkProgressBar would flash if it didn't have its own double
buffer.

> Can a
> redraw somehow be forced? I need to do this, because a timeout will
> periodically call a repaint to all visible progressbars.

Well, you are looking to do something awful anyways (call
gtk_widget_queue_draw() out of a theme engine), so given that, you
could investigate the further awfulness of doing:

 GTK_PROGRESS_GET_CLASS(progressbar)->paint (GTK_PROGRESS(progressbar));
 gtk_widget_queue_draw (progressbar);

> Jimmac's animated scrollbar mockup can be found here:
> http://jimmac.musichall.cz/weblog.php/Design/Progress.php
>
> It appears that a GtkButton has a NO_WINDOW and MAPPED widget flag,
> while GtkProgressBar has not. I'm not sure if either one has something
> to do with it, since I can't really find any straight answers in the
> documentation.

I think you are going to run into the problem that apps frequently
put up a progress bar and only run the main loop occasioanlly to
update the progress bar when the application changes the value ...
that is, you aren't going to get a nice smooth animation.

Regards,
						Owen