Sets the current header of the @row. This is only allowed to be called from a #GtkListBoxUpdateHeaderFunc. It will replace any existing header in the row, and be shown in front of the row in the listbox.
the header, or %NULL
3.10
See Implementation
Sets the current header of the @row. This is only allowed to be called from a #GtkListBoxUpdateHeaderFunc. It will replace any existing header in the row, and be shown in front of the row in the listbox.