Re: forcing immediate redraw on widget

[Gus Koppel <gtk spamkiller bytechase cx>]

Marc Santhoff wrote:

> > So changing the attribute (BG colour) of the GtkHScale basically
> > works for you but your problem is still that it doesn't get
> > completely redrawn immediately? So your problem is simply that the
> > lines
> >
> >     gtk_widget_queue_draw (widget_to_redraw);
> >     while (gtk_events_pending ())
> >         gtk_main_iteration ();
> >
> > have no effect at all for you? You know, you have to place those
> > lines
>
> Yes, exactly.
>
> > after(!) the location where you change the attributes of the widget,
> > i.e. your former code example!?
>
> Sure, they follow directly after the changing code. :)
>
> If this works on GtkHScales at all, i wonder why it doesn't for me.
> The only thing to mention is that the function doing this is called
> from a generic event handler (bound on both hscales at "event") for
> catching special keystrokes (F5...F8). If a key is trapped the
> function returns TRUE for signalling the event is handled, otherwise
> returning FALSE.
>
> Any further ideas?

Nothing concrete at the moment. Since I don't use GTK+ 1.2 and I'm not
planning to install its sources I can only speculate.

Typical speculations would include bad multi-threading voodoo in your
program, another bug somewhere else in your program which left GTK+ in
an inconsistent state, or implementation shortcomings of either
- the gtk_widget_queue_draw () function in GTK+ 1.2
- the Pascal environment you're using to program GTK+ 1.2
- the GtkHScale, especially its redrawing procedures, in GTK+ 1.2
- your graphics driver

It would be interesting to learn whether the GTK+ main loop gets called
after you invalidated the widget. Unfortunately I don't know an easy and
reliable way for a callback function to get invoked each time the main
loop starts an iteration. But you may try this workaround to find out:

/* Process and remove all previously pending events */
    while (gtk_events_pending ())
        gtk_main_iteration ();
/* Verify that 0 == 0 still */
    printf ("gtk_events_pending (should be 0): %d\n",
            gtk_events_pending ());
/* Invalidate widget, should generate new event */
    gtk_widget_queue_draw (widget_to_redraw);
/* Check whether GTK+ knows about a new event pending */
    printf ("gtk_events_pending (should NOT be 0): %d\n",
            gtk_events_pending ());

If especially the second result is "0" then I would suspect an erroneous
or missing implementation of gtk_widget_queue_draw () in GTK+ 1.2. This
would seriously reduce your chances of fixing your problem in GTK+ 1.2.
You know, there are already newer versions available.

Since you're apparently programming GTK+ in Pascal (which one and which
platform, btw?) you will need to slightly adapt those lines, of course.