程序代码如下所以：

unit REdit;

interface

uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
StdCtrls;

type
TCustomREdit = class(TCustomEdit)
private
{ Private declarations }
FAlignment:TAlignment;
procedure SetAlignment(Value: TAlignment);
protected
{ Protected declarations }
     property Alignment: TAlignment read FAlignment write SetAlignment default taLeftJustify;
     procedure CreateParams(var Params: TCreateParams); override;
     public
       { Public declarations }
             published
          { Published declarations }
end;

TREdit = class(TCustomREdit)
published
{ Published declarations }
property Alignment;
property Anchors;
property AutoSelect;
property AutoSize;
property BiDiMode;
property BorderStyle;
property CharCase;
property Color;
property Constraints;
property Ctl3D;
property DragCursor;
property DragKind;
property DragMode;
property Enabled;
property Font;
property HideSelection;
property ImeMode;
property ImeName;
property MaxLength;
property OEMConvert;
property ParentBiDiMode;
property ParentColor;
property ParentCtl3D;
property ParentFont;
property ParentShowHint;
property PasswordChar;
property PopupMenu;
property ReadOnly;
property ShowHint;
property TabOrder;
property TabStop;
property Text;
property Visible;
property OnChange;
property OnClick;
property OnContextPopup;
property OnDblClick;
property OnDragDrop;
property OnDragOver;
property OnEndDock;
property OnEndDrag;
property OnEnter;
property OnExit;
property OnKeyDown;
property OnKeyPress;
property OnKeyUp;
property OnMouseDown;
property OnMouseMove;
property OnMouseUp;
property OnStartDock;
property OnStartDrag;
end;

procedure Register;

implementation

procedure TCustomREdit.CreateParams(var Params: TCreateParams);
const
Alignments: array[Boolean, TAlignment] of DWORD =
((ES_LEFT, ES_RIGHT, ES_CENTER),(ES_RIGHT, ES_LEFT, ES_CENTER));
begin
   inherited CreateParams(Params);
   with Params do
      begin
        Style := Style or Alignments[UseRightToLeftAlignment, FAlignment];
      end;
end;

procedure TCustomRedit.SetAlignment(Value:TAlignment);
begin
  if FAlignment <> Value then
     begin
       FAlignment := Value;
       RecreateWnd;
     end;
end;

procedure Register;
begin
     RegisterComponents('Samples', [TREdit]);
   end;

end.

上述只是给初学Delphi控件制作者一点参考，当然不入方家法眼。不足之处，敬请指正。