A
GPropertyAction is a way to get a
Action with a
state value reflecting and controlling the value of a
Object
property.
The state of the action will correspond to the value of the property.
Changing it will change the property (assuming the requested value
matches the requirements as specified in the
[type
gObject.ParamSpec]).
Only the most common types are presently supported. Booleans are
mapped to booleans, strings to strings, signed/unsigned integers to
int32/uint32 and floats and doubles to doubles.
If the property is an enum then the state will be string-typed and
conversion will automatically be performed between the enum value and
‘nick’ string as per the [type
gObject.EnumValue]
table.
Flags types are not currently supported.
Properties of object types, boxed types and pointer types are not
supported and probably never will be.
Properties of [type
gLib.Variant] types are not
currently supported.
If the property is boolean-valued then the action will have a
NULL parameter type, and activating the action (with no
parameter) will toggle the value of the property.
In all other cases, the parameter type will correspond to the type of
the property.
The general idea here is to reduce the number of locations where a
particular piece of state is kept (and therefore has to be
synchronised between).
GPropertyAction does not have a
separate state that is kept in sync with the property value — its
state is the property value.
For example, it might be useful to create a
Action
corresponding to the
visible-child-name property of a
`GtkStack` so that the current page can be switched from a
menu. The active radio indication in the menu is then directly
determined from the active page of the
GtkStack.
An anti-example would be binding the
active-id property on a
`GtkComboBox`. This is because the state of the combo box
itself is probably uninteresting and is actually being used to control
something else.
Another anti-example would be to bind to the
visible-child-name property of a
`GtkStack` if this
value is actually stored in
Settings. In that case, the real
source of the value is*
Settings. If you want a
Action
to control a setting stored in
Settings, see
settingsCreateAction instead, and possibly combine its use with
settingsBind.
Since: 2.38