Re: GtkButton GtkHScale

["Brian J. Tarricone" <bjt23 cornell edu>]

On Mon, 19 Jul 2004, Johannes Postma wrote:

> Hello,
>
> I have an application with a GtkButton and a GtkHScale.The button is
> used to set the value of the GtkHScale. Unfortunately my code doesn't
> work. I get the next error:
>
> Gtk-CRITICAL **: file gtkrange.c: line 669 (gtk_range_set_value):
> assertion `GTK_IS_RANGE (range)' failed
>
> My code is:
>
> void on_BUTTON_clicked (GtkButton *button, gpointer user_data)
> {
>       GtkHScale *scale = (GtkHScale *)g_object_get_data(G_OBJECT(button),
> "hscale1");
>       gtk_range_set_value(GTK_HSCALE(scale), 0);  
> }
>
> Can someone help me?

you're probably looking for something like this:
{
        GtkRange *range = GTK_RANGE(g_object_get_data(....));
        gtk_range_set_value(range, 0);
}

gtk_range_set_value() expects a GtkRange as the first parameter 
(GtkHScale is a subclass of GtkScale which is a subclass of GtkRange).  
also, make sure you're using g_object_set_data() correctly to set 
"hscale1" to the proper widget.

however, there's a better way of doing all this:

/* where the scale/button are created */
hscale1 = gtk_hscale_new(...);
/* some stuff */
button = gtk_button_new();
/* some more stuff */
g_signal_connect(G_OBJECT(button), "clicked",
        G_CALLBACK(on_BUTTON_clicked), hscale1);
/*                        note here:   ^^^^^^^  */

then you don't need to worry about g_object_{set,get}_data():

void on_BUTTON_clicked(GtkButton *b, gpointer user_data)
{
        GtkRange *hscale1 = user_data;
        gtk_range_set_value(hscale1, 0);
}

hope this helps,
brian