TreeViewColumnDropFunc
Description:
[ Version ( deprecated = true , deprecated_since = "4.20" ) ]
public delegate bool TreeViewColumnDropFunc (TreeView tree_view, TreeViewColumn column, TreeViewColumn prev_column, TreeViewColumn next_column)
Warning: TreeViewColumnDropFunc is deprecated since 4.20.
Function type for determining whether column can be dropped in a particular spot (as determined by prev_column and 
      next_column).
There is no replacement.
 In left to right locales, prev_column is on the left of the potential drop spot, and next_column is on the right. In
       right to left mode, this is reversed. This function should return true if the spot is a valid drop spot. 
      Please note that returning true does not actually indicate that the column drop was made, but is meant only to
       indicate a possible drop spot to the user.
Parameters:
| tree_view | 
           A `GtkTreeView`  | 
      
| column | 
           The `GtkTreeViewColumn` being dragged  | 
      
| prev_column | 
           A `GtkTreeViewColumn` on one side of   | 
      
| next_column | 
           A `GtkTreeViewColumn` on the other side of   | 
      
| data | 
           user data  | 
      
Returns:
| 
           true, if   |