* @defgroup Elm_Radio Radio
* @ingroup Elementary
* @image html radio_inheritance_tree.png
* @image latex radio_inheritance_tree.eps
* @image html img/widget/radio/preview-00.png
* @image latex img/widget/radio/preview-00.eps
* @brief Radio is a widget that allows for 1 or more options to be displayed
* and have the user choose only 1 of them.
* A radio object contains an indicator, an optional Label and an optional
* icon object. While it's possible to have a group of only one radio they,
* are normally used in groups of 2 or more.
* elm_radio objects are grouped in a slightly different, compared to other
* UI toolkits. There is no separate group name/id to remember or manage.
* The members represent the group, there are the group. To make a group,
* use elm_radio_group_add() and pass existing radio object and the new radio
* The radio object(s) will select from one of a set
* of integer values, so any value they are configuring needs to be mapped to
* a set of integers. To configure what value that radio object represents,
* use elm_radio_state_value_set() to set the integer it represents. To set
* the value the whole group(which one is currently selected) is to indicate
* use elm_radio_value_set() on any group member, and to get the groups value
* use elm_radio_value_get(). For convenience the radio objects are also able
* to directly set an integer(int) to the value that is selected. To specify
* the pointer to this integer to modify, use elm_radio_value_pointer_set().
* The radio objects will modify this directly. That implies the pointer must
* point to valid memory for as long as the radio objects exist.
* This widget inherits from the @ref Layout one, so that all the
* functions acting on it also work for radio objects.
* This widget emits the following signals, besides the ones sent from
* @ref Layout:
* @li @c "changed" - This is called when the radio object is selected. If you
* want to trace the state change of a radio group, you should add this callback
* to all the radio objects in that group.
* @li @c "focused" - When the radio has received focus. (since 1.8)
* @li @c "unfocused" - When the radio has lost focus. (since 1.8)
* @li @c "language,changed" - the program's language changed (since 1.9)
* Default content parts of the radio widget that you can use for are:
* @li "icon" - An icon of the radio
* Default text parts of the radio widget that you can use for are:
* @li "default" - A label of the radio
* Supported elm_object common APIs.
* @li @ref elm_object_part_text_set
* @li @ref elm_object_part_text_get
* @li @ref elm_object_part_content_set
* @li @ref elm_object_part_content_get
* @li @ref elm_object_part_content_unset
* @li @ref elm_object_disabled_set
* @li @ref elm_object_disabled_get
* @ref tutorial_radio show most of this API in action.