Sets a header function.
By setting a header function on the this one can dynamically add headers in front of rows, depending on the contents of the row and its position in the list.
For instance, one could use it to add headers in front of the first item of a new kind, in a list sorted by the kind.
The update_header can look at the current header widget using [[email protected]_header] and either update the state
of the widget as needed, or set a new one using [[email protected]_header]. If no header is needed, set the header to
null.
Note that you may get many calls update_header to this for a particular row when e.g. changing things that don’t affect
the header. In this case it is important for performance to not blindly replace an existing header with an identical one.
The update_header function will be called for each row after the call, and it will continue to be called each time a row
changes (via [[email protected]]) and when the row before changes (either by [[email protected]] on the previous
row, or when the previous row becomes a different row). It is also called for all rows when [[email protected]_headers] is
called.
| this |
a `GtkListBox` |
| update_header |
callback that lets you add row headers |
| destroy |
destroy notifier for |
| user_data |
user data passed to |