Murray Cumming wrote:
> On Thu, 2006-07-06 at 23:07 +0300, Paul Pogonyshev wrote:
> > Yes, but this should be done in the library. All this classes should belong
> > to Gtkmm and you don't write them yourselves. Tracking sensitivity or
> > visibility is a common task and any non-trivial application does that. Why
> > not transfer this common task to the GUI library (Gtkmm)?
>
> I have not read this whole thread, and I'm not going to - it's far too
> verbose. But I might read a short summary that shows me clearly
> a) What people apparently have to do repeatedly now with gtkmm..
It is a very common task to change sensitivity of a widget. Less so to
change its visibility.
> b) What people would do instead with this new thing.
Currently, you have to 1) set sensitivity (some state) to a computed value;
2) track when that computed value changes its state, by connecting to the
appropriate callbacks; if the rules change, you have to not forget to keep
the computation and state tracking in sync; and 3) set the initial state
(sometimes). Note that the initial state should also be in sync with
points 1) and 2).
I propose to do all the steps at once, using `condition's. This roughly
corresponds to step 1), while all the rest is done automatically.
Using conditions (doesn't work currently, of course; how it should look
like):
button->set_sensitive (entry->get_not_empty_condition () &
check_button->get_active_condition ());
Traditional method:
entry->signal_changed ().connect (sigc::mem_fun (*this,
&Windows::update_sensitivity));
check_button->signal_toggled ().connect (sigc::mem_fun (*this,
&Windows::update_sensitivity));
// Set initial state.
update_sensitivity ();
...
void
update_sensitivity ()
{
button->set_sensitive (entry->get_text_length () > 0 &&
check_button->get_active ());
}
> Note also that you can already get notification of property changes from
> gtkmm objects, like so:
> widget.property_something().signal_changed().connect( ... )
Yes. I propose to simplify it (writing less code) and make less error-
prone (all is done only once and in one place.) This is at a small
cost to efficiency, which is not important in GUI.
Paul
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