Thank you very much for the very detailed responses are helpful.
Long time no do anything in C or Java, since I discovered python not write
in another language. vala seems excellent among other things because I can
run my python application to vala practically without changes.
Hence come my difficulties with these functions.
In python get_toplevel () always returns the main Gtk.Window of apicación.
Get the value of any property is made by GET_PROPERTY ("property_name"),
etc. . .
These details are important for code clarity for those who got to vala from
python.
2014-12-20 2:36 GMT-02:00 Evan Nemerson <[email protected]>:
> On Sat, 2014-12-20 at 00:51 -0200, Flavio Danesse wrote:
> > Another thing that does not work as expected is:
> >
> > this.get_toplevel ()
> >
> > This should return the main application window, or one Gtk.Window, but
> > returns a Gtk.Widget
>
> Because that's what the C function does. The documentation describes
> when the return value will *not* be a Gtk.Window. See
>
> https://developer.gnome.org/gtk3/stable/GtkWidget.html#gtk-widget-get-toplevel
>
> > 2014-12-20 0:32 GMT-02:00 Flavio Danesse <[email protected]>:
> >
> > > I understand, but it is logical that a get back what is asked, things
> like
> > > that are not logical fol:
> > >
> > > error: invocation of void method not allowed as expression
> > > this.get_property("type");
>
> Not sure where you're getting that error from—trying to call
> GLib.Object.get_property like that here results in:
>
> error: 1 missing arguments for `void GLib.Object.get_property
> (string property_name, ref GLib.Value value)'
>
> As for why it returns void instead of GLib.Value, look at the C
> function:
>
> https://developer.gnome.org/gobject/stable/gobject-The-Base-Object-Type.html#g-object-get-property
>
> > >
> > > In the initial example:
> > > this.get_allocation()
> > > does not work, though:
> > > this.get_allocated_width()
> > > if it works.
>
> This is a more interesting example, but again it's a reflection of the C
> API:
>
>
> https://developer.gnome.org/gtk3/stable/GtkWidget.html#gtk-widget-get-allocation
>
> https://developer.gnome.org/gtk3/stable/GtkWidget.html#gtk-widget-get-allocated-width
>
> For this function it would actually be possible to alter the bindings to
>
> public Gtk.Allocation get_allocation ();
>
> Actually, these days it is generated like that by default, but we have a
> line in our metadata file to change it back to avoid breaking backwards
> compatibility.
>
> Also, we have to be careful changing out params to return values like
> that since in the future the C API may change to include a return value
> (which isn't an API break for the C API). That happened recently in
> GtkSourceview and it broke several Vala programs. See
> https://bugzilla.gnome.org/show_bug.cgi?id=738896
>
>
>
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