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。