CustomSort triggers node sorting or resorting, using a comparison routine indicated by the SortProc parameter. 

The Data parameter provides a way to pass information to a customized comparison routine. Data is not used by the CustomSort method or the default comparison routine. 

The optional ARecurse parameter (default false) specifies that sorting should recursively descend the node tree and sort each subtree in turn. 

The Return Value of CustomSort indicates the success status of the sort. 

If SortProc is nil (Delphi) or NULL (C++), a default comparison routine is used. The default routine uses the OnCompare event handler for the associated TCustomTreeView object, if defined. If the OnCompare event handler is not defined, the default routine uses a simple case-sensitive compare of node captions. 

The comparison routine is defined like this:

Pascal
         TTVCompare = function(lParam1, lParam2, lParamSort: Longint): Integer;
         
         C++
         typedef int (CALLBACK *TTVCompare)(LPARAM lParam1, LPARAM lParam2, LPARAM lParamSort);

The lParam1 and lParam2 parameters refer to two nodes when cast to TTreeNode. 

The lParamSort parameter is the value previously passed in the Data parameter of CustomSort. 

The Return Value of the comparison routine indicates the relative sort order of IParam1 and IParam2:

CustomSort