add_button
Description:
Adds a button to this that activates the action in detailed_action when clicked.
That action must be an application-wide action (starting with "app."). If detailed_action contains a target, the action will be
activated with that target as its parameter.
See parse_detailed_name for a description of the format for
detailed_action.
Parameters:
| this | |
| label |
label of the button |
| detailed_action |
a detailed action name |