ControlState
Parameters
Current value of the control (edited by the user) - MutableState.
Original value loaded from the database or set as a default - MutableState.
Text shown to the user when it cannot be derived from value on every render: the edit buffer of a number field (1. is not a number yet) or the label of the selected dropdown item (needs a query). null means "not determined" - the control fills it in itself, synchronously or with a query. That is why updateControl from outside clears this field: writing the value invalidates the text, and the clearing itself is the signal to work it out again.
Label overridden from an action, in place of the one from the schema.
Type Parameters
Type of the data held by the control.