自定义可折叠的控件属性的问题

如下代码：自定义控件的一个属性，希望把几个属性集中到一个条目下
点击前面的加号后，展开其内部的属性。
下面的程序，运行后在属性列表内有
+visibility，但是点击后下面没有内容，为什么？
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unit SDProperty;

interface
uses SysUtils, Classes;
type Tvisibility=class(Tobject)
private
FVisible:boolean;
FVFrom:integer;
FVTo:integer;
procedure setvisible(value:boolean);
procedure setVFrom(value:integer);
procedure setVTo(value:integer);
protected
public
constructor create;
destructor destroy; override;
published
property Visible:boolean read Fvisible write setvisible default true;
property VFrom:integer read FVFrom write setVFrom default 0;
property VTo:integer read FVTo write setVTo default 0;

end;
//procedure Register;
Implementation
constructor TVisibility.create;
begin
Fvisible:=true;
FVFrom:=0;
FVTo:=0;
end;
destructor TVisibility.destroy;
begin
inherited;
end;
procedure TVisibility.setvisible(value:boolean);
begin
FVisible:=value;
end;
procedure Tvisibility.setVFrom(value:integer);
begin
FVFrom:=value;
end;
procedure TVisibility.setVTo(value:integer);
begin
FVTo:=value;
end;
end.