Block a signal seems not to work

["Peter T. Mayer" <peter_t_mayer yahoo de>]

Hello,

After I have irked myself for 3 days with blocking a signal and couldn't 
find a solution I ask here for help:

I connect a signal handler as follows:

g_signal_connect ((gpointer) hscale1, "value_changed",
                   G_CALLBACK (on_hscale1_value_changed),
                   NULL);

and this is the corresonding callback function:

void
on_hscale1_value_changed    (GtkRange        *range,
                            gpointer         user_data)
{
   double oldtime= gtk_range_get_value (range);
   g_signal_handlers_block_by_func ((gpointer) range, G_CALLBACK 
(on_hscale1_value_changed), NULL);
   double newtime= go_to_position (GTK_WIDGET (range), oldtime);
   gtk_range_set_value (range, newtime );
   g_signal_handlers_unblock_by_func ((gpointer) range, G_CALLBACK 
(on_hscale1_value_changed), NULL);
}

The function go_to_position calculates newtime by finding the nearest 
possible value around oldtime, this means oldtime will always differ 
slightly from newtime. Now I want to display the correct value and not 
the one which was set by the user. So I call "gtk_range_set_value 
(range, newtime );". But then the callback is called again (because the 
value has changed to newtime). The problem is that in most cases 
"newtime= go_to_position (GTK_WIDGET (range), oldtime);" will give you a 
different newtime value, even if in the function call before oldtime was 
already calculated by go_to_position. So you get an never ending loop. 
This happens also, if you block (as shown above) or even disconnect the 
handler. If for testing purposes I only block and do not unblock the 
signal (comment out the last line of on_hscale1_value_changed), this 
works as expected. So the signal must be stored until I unblock the handler.

If you want to test the described case write the following 
go_to_position function:

double go_to_position( GtkWidget *dialog, double seconds ) {
   printf( "Time: %.1f\n", seconds );
   return seconds+0.1;
}

How could I stop this behavior?

Thanks,
Peter!