Every button has a button type, which defines default values for the button’s properties. Button types are arranged in a hierarchy, with specialized types inheriting from more general types, so that it’s easy to define special-purpose types of buttons for specific tasks.
function define-button-type name \&rest properties
Define a button type called
name (a symbol). The remaining arguments form a sequence of
property value pairs, specifying default property values for buttons with this type (a button’s type may be set by giving it a
type property when creating the button, using the
:type keyword argument).
In addition, the keyword argument
:supertype may be used to specify a button-type from which
name inherits its default property values. Note that this inheritance happens only when
name is defined; subsequent changes to a supertype are not reflected in its subtypes.
define-button-type to define default properties for buttons is not necessary—buttons without any specified type use the built-in button-type
button—but it is encouraged, since doing so usually makes the resulting code clearer and more efficient.