Re: [gtk-list] RE: entry input verification [Was: Uppercase only ent

[Owen Taylor <otaylor redhat com>]

Trog <trog@gtk.org> writes:

> On 29-Feb-2000 Ralf Corsepius wrote:
> > On a related subject (It might be an FAQ, but ...):
> 
> [NOTE to self] write a FAQ entry for this.
> 
> > 
> > I am looking for a method to provide input verification on
> > GtkEntry/GtkEditable, e.g. I am looking for an GtkEditable which
> > shall only
> > accept a subset of characters (eg. those that match a regular
> > expression, or
> > integers only) as text input.
> > 
> > [Actually, I  looking for something similar to Motif's
> > XmNmodifyVerifyCallback
> > for XmTextFieldWidgets]
> > 
> > The approach you outline above doesn't seem to work in my case,
> > because the
> > insert_text signal does't seem to allow changing the size of the
> > inserted
> > text.
> > Implementing it with the changed signal seems to be possible, but
> > seems to be
> > rather ineffective and also seems to suffer from the "infinite
> > loop" issue
> > (changed being called because invoking "set_text" ).
> 
> Attach to the "key_press_event" event of the entry widget:
> 
> gtk_signal_connect(GTK_OBJECT(entry),
>                    "key_press_event"
>                    GTK_SIGNAL_FUNC(entry_key_press),
>                    data);
> 
> Then the callback function goes along the lines:
> 
> gint entry_key_press (GtkWidget *widget,
>                       GdkEventKey *event,
>                       gpointer     data)
> {
>   switch (event->keyval) {
>   case GDK_F1:
>    gtk_signal_emit_stop_by_name(GTK_OBJECT(widget),"key_press_event");
>    gtk_editable_insert_text( GTK_EDITABLE(widget), "hello",
>                              5,&GTK_EDITABLE(widget)->current_pos);
>    return TRUE;
> 
>   case GDK_F2:
>    gtk_signal_emit_stop_by_name(GTK_OBJECT(widget),"key_press_event");
>    gtk_editable_insert_text( GTK_EDITABLE(widget), "world",
>                              5,&GTK_EDITABLE(widget)->current_pos);
>    return TRUE;
>   }
> 
>   return FALSE;
> }
> 
> I think that covers what you need. Well, you should get the idea
> anyway.

This isn't a good approach, because if you do it this way, the
user will be able to cut-and-paste invalid input into the entry,
even if they can't edit it directly.

See the example in the GtkEditable reference docs:

 http://developer.gnome.org/doc/API/gtk/gtkeditable.html

For a completion implementation of the method that Havoc has
described.

Regards,
                                        Owen