Request for the state of this to be changed to value.
The action must be stateful and value must be of the correct type. See
get_state_type.
This call merely requests a change. The action may refuse to change its state or may change its state to something other than value
. See get_state_hint.
If the value GVariant is floating, it is consumed.
| this |
a Action |
| value |
the new state |