 -- Class: <gtk-tree-drag-source>
     Derives from <ginterface>.

     This class defines no direct slots.

 -- Class: <gtk-tree-drag-dest>
     Derives from <ginterface>.

     This class defines no direct slots.

 -- Function: gtk-tree-drag-source-drag-data-get (self <gtk-tree-drag-source>) (path <gtk-tree-path>) (selection_data <gtk-selection-data>) =>  (ret bool)
 -- Method: drag-data-get
     Asks the <gtk-tree-drag-source> to fill in SELECTION-DATA with a representation of the row at PATH. SELECTION-DATA->TARGET gives the required type of the data. Should robustly handle a PATH no longer found in the model!

     drag-source
          a <gtk-tree-drag-source>

     path
          row that was dragged

     selection-data
          a <gtk-selection-data> to fill with data from the dragged row

     ret
          #t if data of the required type was provided

 -- Function: gtk-tree-drag-source-row-draggable (self <gtk-tree-drag-source>) (path <gtk-tree-path>) =>  (ret bool)
 -- Method: row-draggable
     Asks the <gtk-tree-drag-source> whether a particular row can be used as the source of a DND operation. If the source doesn't implement this interface, the row is assumed draggable.

     drag-source
          a <gtk-tree-drag-source>

     path
          row on which user is initiating a drag

     ret
          #t if the row can be dragged

 -- Function: gtk-tree-set-row-drag-data (self <gtk-selection-data>) (tree_model <gtk-tree-model>) (path <gtk-tree-path>) =>  (ret bool)
     Sets selection data of target type GTK_TREE_MODEL_ROW. Normally used in a drag_data_get handler.

     selection-data
          some <gtk-selection-data>

     tree-model
          a <gtk-tree-model>

     path
          a row in TREE-MODEL

     ret
          #t if the <gtk-selection-data> had the proper target type to allow us to set a tree row