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procedure OnReadOnlyChanged(var Msg: TMessage); message EM_SETREADONLY;					

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procedure TJEdit.OnReadOnlyChanged(var Msg: TMessage);
begin
  if ReadOnly then Color:= clGray;
  if not ReadOnly then Color:= clWhite;
end;					

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type
  TSomeClass = class
  private
    FPropertyname: SomeType;
    procedure SetPropertyname(const Value: SomeType);
  public
    property Propertyname: SomeType read FPropertyName write SetPropertyname;
  end;

procedure TSomeClass.SetPropertyname(const Value: SomeType);
begin
  FPropertyname := Value;
end;					

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unit TestEdit;

interface

uses Classes, Controls, StdCtrls, Graphics;

type
  TTestEdit = class(TCustomEdit)
  private
    function GetReadOnly: Boolean;
    procedure SetReadOnly(const Value: Boolean);
  public
    constructor Create(AOwner: TComponent); override;
  published
    property ReadOnly: Boolean read GetReadOnly write SetReadOnly;
    property Align;
    property Alignment;
    property Anchors;
    property AutoSelect;
    property AutoSize;
    property BevelEdges;
    property BevelInner;
    property BevelKind default bkNone;
    property BevelOuter;
    property BevelWidth;
    property BiDiMode;
    property BorderStyle;
    property CharCase;
    property Color;
    property Constraints;
    property Ctl3D;
    property DoubleBuffered;
    property DragCursor;
    property DragKind;
    property DragMode;
    property Enabled;
    property Font;
    property HideSelection;
    property ImeMode;
    property ImeName;
    property MaxLength;
    property NumbersOnly;
    property OEMConvert;
    property ParentBiDiMode;
    property ParentColor;
    property ParentCtl3D;
    property ParentDoubleBuffered;
    property ParentFont;
    property ParentShowHint;
    property PasswordChar;
    property PopupMenu;
    property ShowHint;
    property TabOrder;
    property TabStop;
    property Text;
    property TextHint;
    property Touch;
    property Visible;
    property OnChange;
    property OnClick;
    property OnContextPopup;
    property OnDblClick;
    property OnDragDrop;
    property OnDragOver;
    property OnEndDock;
    property OnEndDrag;
    property OnEnter;
    property OnExit;
    property OnGesture;
    property OnKeyDown;
    property OnKeyPress;
    property OnKeyUp;
    property OnMouseActivate;
    property OnMouseDown;
    property OnMouseEnter;
    property OnMouseLeave;
    property OnMouseMove;
    property OnMouseUp;
    property OnStartDock;
    property OnStartDrag;
  end;

procedure Register;

implementation

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

{ TTestEdit }

constructor TTestEdit.Create(AOwner: TComponent);
begin
  inherited;
  ReadOnly := inherited ReadOnly;
end;

function TTestEdit.GetReadOnly: Boolean;
begin
  Result := inherited ReadOnly;
end;

procedure TTestEdit.SetReadOnly(const Value: Boolean);
begin
  inherited ReadOnly := Value;
  if Value then
    Font.Color := clRed
  else
    Font.Color := clGreen;
end;

end.					

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  published
    property ReadOnly: Boolean read GetReadOnly write SetReadOnly;