Re: cancelling/aborting an emitted signal

On Tue, 2002-02-26 at 19:03, Paul Davis wrote:
> >Hello,
> >
> >Can someone suggest the proper generic way to abort a signal from
> >actually causing the default handler to change the widget value. Must I
> >connect the signal handler in a certain order?
> >
> >For example, in a "toggled" signal handler for a toggle button if some
> >condition is true then I want the "toggled" signal to be canceled so the
> >widget does not signify the change (a checkmark displayed or removed).
> >I've tried the following but get a Gtk Warning indicating there is to no
> >emitted signal to stop:
> >
> >gtk_signal_emit_stop_by_name (GTK_OBJECT (button), "toggled");
> catch the button_press_event and you'll probably find that you're in
> better shape. also, check and double check that you're calling it on
> the correct widget - i've sometimes done cut-n-paste ops that have led
> to that error message.
> >Again, I want to know the generic method to cancel a signal within a
> >signal handler so the widget does not reflect the change. This applies
> >to GtkAdjustment value changes (for GtkHScale and GtkSpinButton
> >changes), GtkCList row selection and unselection, and others.
> i do this a LOT in my code, and i always use
> gtk_signal_emit_stop_by_name(), but i always catch the underlying
> events (button press/release etc.), not the "translations" like
> clicked/selected/activate and so forth.
> you also need to still return TRUE, sometimes.
> --p


Sorry, for the delayed question but I was on holiday this week.

So if I understand correctly, I shouldn't connect a signal handler to
something like "toggled" but something like "button_press_event" and
check whether it is button 1 that was clicked?

My original code looks like this:

void on_option_check_button_toggled (GtkToggleButton *button,
option_widget_info_t *info)
    gint     rc;
    value_t  value;
    gboolean value_changed;

    value.bool = gtk_toggle_button_get_active (button);

    rc = set_widget_option_value (info, &value, &value_changed);

    if (rc == SUCCESS)
        if (value_changed)
            gtk_signal_handler_block_by_func (GTK_OBJECT (button),
on_option_check_button_toggled, info);
            gtk_toggle_button_set_active (button, value.bool);
            gtk_signal_handler_unblock_by_func (GTK_OBJECT (button),
on_option_check_button_toggled, info);
            info->value.bool = value.bool;
        gtk_signal_emit_stop_by_name (GTK_OBJECT (button), "toggled");


Do you know a) will the gtk_toggle_button_get_active() still work as
expected in the new handler and b) will calling
gtk_signal_emit_stop_by_name for the "button_press_event" actually
cancel the signal and revert the toggle button to its original state?

Also, do I have to setup identical signal handlers for using the
keyboard, i.e. "key_press_event" since I am not using the

Is this really going to do what I want which is undo the event and
revert to original state?


Luciano Chavez

lnx1138 us ibm com 

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