Adds this to the group of group.
In a group of multiple check buttons, only one button can be active at a time. The behavior of a checkbutton in a group is also commonly known as a *radio button*.
Setting the group of a check button also changes the css name of the indicator widget's CSS node to 'radio'.
Setting up groups in a cycle leads to undefined behavior.
Note that the same effect can be achieved via the [[email protected]] API, by using the same action with parameter type and state type 's' for all buttons in the group, and giving each button its own target value.
| this |
a `GtkCheckButton` |
| group |
another `GtkCheckButton` to form a group with |