Re: SpinButton: how to avoid calling signal handler when set_value()

[pozzugno <pozzugno gmail com>]

Il 02/11/2016 18:55, Nicola Fontana ha scritto:
> Il Wed, 2 Nov 2016 14:40:58 +0100 Pozz Pozz <pozzugno gmail com> scrisse:
>
> > 2016-11-02 11:24 GMT+01:00 Nicola Fontana <ntd entidi it>:
> > > ...
> > >
> > > you don't necessarily need the handler id. In C (I don't use
> > > python) you could write the following:
> > >
> > > void my_set_value(GtkSpinButton *spin_button, gdouble value)
> > > {
> > >      g_signal_handlers_block_matched(spin_button,
> > >                                      G_SIGNAL_MATCH_FUNC,
> > >                                      0, 0, NULL,
> > >                                      callback_to_skip,
> > >                                      NULL);
> > >
> > >      /* This will not trigger callback_to_skip */
> > >      gtk_spin_button_set_value(spin_button, value)
> > >
> > >      g_signal_handlers_unblock_matched(spin_button,
> > >                                        G_SIGNAL_MATCH_FUNC,
> > >                                        0, 0, NULL,
> > >                                        callback_to_skip,
> > >                                        NULL);
> > > }
> > >   
> > I got the idea. I don't know if g_signal_handlers_block_matched() or
> > similar functionality is available in Python. However, remaining in C, your
> > code make the assumption there is a single callback function for all the
> > spinbuttons. This is not true: I have a different handler for each
> > spinbutton, because I have to make different things.
> Sorry but I am a developer, not a mind reader.
Yes, of course :-) Thank you for spending some time for me.

I thought using a different callback for each SpinButton was the more 
typical solution.

> You can match by data or try to lookup the callback by detail with
> g_signal_handler_find or refactor your code to use a single
> callback.
It seems pyGObject implementation gives only two "handler block" 
functions: handler_block(), that needs the handler_id that I don't have; 
handler_block_by_func() that needs the callback to block (the same 
problem of your solution, because I have different callbacks).

Is it possible to retrieve the list of connected callbacks of an object 
and a signal name ("value-changed")?

> The fact that you are using different callbacks has a
> foul smell indeed.
Yes? I have to generate and send a different request to the device. Why 
do you think it's better to have a single callback?
Of course, I could write one single callback as:

  def callback(self, spinbutton):
    if spinbutton is spinSetting1:
      self.callback_setting1(spinbutton)
    elif spinbutton is spinSetting2:
      self.callback_setting2(spinbutton)
    ...

  def callback_setting1(self,spinbutton):
    # This is the callback of the spinbutton associated to setting1 
parameter
    set_setting1(spinbutton.get_value())

It seems to me a more complicated way to write different callbacks.

IMHO the solution to use a refreshing flag is the simplest solution, 
even if a little dirty. Alternatively, I have to create a list of 
spinbuttons *and* callbacks and search for the callback to unblock in 
your suggested function my_set_value().

> Come on, a little bit of initiative. Here, today only, the link to
> the official (C) documentation:
>
> https://developer.gnome.org/gobject/stable/gobject-Signals.html
Please, don't think I don't use to read documentation.