Re: Invisible GtkImage

[Andrew Potter <agpotter gmail com>]

On Thu, Jun 13, 2013 at 9:54 PM, Kip Warner <kip thevertigo com> wrote:
> > What you can do to (try to) prevent that situation is to set the widget to
> > do "height for width" allocation, and override
> > get_preferred_height_for_width() to honor your aspect ratio. In some
> > situations of course the toolkit won't be able to perfectly honor the
> > allocation request, so be sure not to scale out of bounds no matter what.
>
> Right. What I will do is resize to exactly what is passed into my
> do_size_allocate() override since that size should theoretically meet
> the aspect ratio I am maintaining via my
> do_get_preferred_height_for_width() override.
>     def do_get_preferred_height_for_width(self, width):
>         return (width / self._aspectRatio)
>
>     def do_get_request_mode(self):
>         return Gtk.SizeRequestMode.HEIGHT_FOR_WIDTH
>
> ...but something very interesting happens immediately after the return
> in do_get_preferred_height_for_width(). I get an assertion fail buried
> deep somewhere in python-gi...


I suspect something weird is happening because you have the wrong
function signature. I can't find any reference to the basic widget
methods on the python gtk documentation website, but the C signature
is:

void                gtk_widget_get_preferred_height_for_width
                                                        (GtkWidget *widget,
                                                         gint width,
                                                         gint *minimum_height,
                                                         gint *natural_height);


So try:
def do_get_preferred_height_for_width(self, width, minimum_height,
natural_height):
  minimum_height = width / self._aspectRatio
  natural_height = width / self._aspectRatio

If that doesn't work, try and find out how the python gintrospection
stuff deals with out parameters.