How to use GObject.GEnum as property type in PyGobject (original) (raw)

February 10, 2025, 6:18am 1

How can I use GObject.GEnum as a property type in PyGobject. For example Gtk.Box has a property halign of type Gtk.Align enum. Now let’s say I’ve the following:

# custom enum
class example_enum(GObject.GEnum):
    PROP0 = 0
    PROP1 = 1

# custom subclass 
class custom_box(Gtk.Box):
    __gproperties__: {
        "example_prop": # property_of_type_example_enum
    }
    # other_stuffs

How can I set example_prop here?

jamesh (James Henstridge) February 13, 2025, 7:37am 2

It isn’t currently possible to register new enumeration types with current stable releases of PyGObject. Support was merged to main earlier today though:

With those changes, your example_enum class definition will automatically register a new GType for the enumeration with the two values you’ve defined. You should then be able to use it the same way as any other registered enumeration:

>>> from gi.repository import GObject
>>> class example_enum(GObject.GEnum):
...     PROP0 = 0
...     PROP1 = 1
... 
>>> example_enum.__gtype__
<GType __main__+example_enum (289342256)>
>>> example_enum.PROP0
<example_enum.PROP0: 0>
>>> example_enum.PROP1
<example_enum.PROP1: 1>

Under the covers, GEnum and GFlags are now subclasses of the standard library enum.IntEnum and enum.IntFlag classes respectively. A custom metaclass is used to hook into the attempt to create a subclass: it notices that example_enum doesn’t have a GType, so registers a new one based on the declared enumeration values.

raVen (Abir Halder) February 17, 2025, 4:28pm 3

Thanks for the reply. Can you please tell me how can I add a GObect.GEnum as a property type with required parameters? In my case for example_enum I’m trying to do it like this:

__gproperties__ = {
    "example_prop": (
        example_enum.__gtype__,
        "example property",
        "An example property",
        GObject.ParamFlags.READABLE
    )
}

And it’s giving an error TypeError: function takes exactly 1 argument (0 given)

system (system) Closed March 19, 2025, 4:28pm 4

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