unit DelphiPt;

interface

uses
  Classes, Graphics;

type
  TDDHPoint = class (TCollectionItem)
  private
    fX, fY: Integer;
  public
    Text: string;
    procedure WriteText (Writer: TWriter);
    procedure ReadText (Reader: TReader);
    procedure DefineProperties (Filer: TFiler); override;
    procedure Paint (Canvas: TCanvas);
    procedure Assign (Pt: TPersistent); override;
  published
    property X: Integer read fX write fX;
    property Y: Integer read fY write fY;
  end;

  TWrapper = class (TComponent)
  private
    FColl: TCollection;
  published
    property MyColl: TCollection read FColl write FColl;
  public
    constructor Create (Owner: TComponent); override;
    destructor Destroy; override;
  end;

implementation

// TWrapper constructor and destructor

constructor TWrapper.Create (Owner: TComponent);
begin
  inherited Create (Owner);
  FColl := TCollection.Create (TDDHPoint);
end;

destructor TWrapper.Destroy;
begin
  FColl.Clear;
  FColl.Free;
  inherited Destroy;
end;


// class TDDHPoint methods

procedure TDDHPoint.WriteText (Writer: TWriter);
begin
  Writer.WriteString (Text);
end;

procedure TDDHPoint.ReadText (Reader: TReader);
begin
  Text := Reader.ReadString;
end;

procedure TDDHPoint.DefineProperties (Filer: TFiler);
begin
  Filer.DefineProperty (
    'Text', ReadText, WriteText, (Text <> ''));
end;

procedure TDDHPoint.Paint (Canvas: TCanvas);
begin
  Canvas.Ellipse (fX - 3, fY - 3, fX + 3, fY + 3);
  Canvas.TextOut (fX + 5, fY + 5, Text);
end;

procedure TDDHPoint.Assign (Pt: TPersistent);
begin
  if Pt is TDDHPoint then
  begin
    fx := TDDHPoint (Pt).fX;
    fY := TDDHPoint (Pt).fY;
    Text := TDDHPoint (Pt).Text;
  end
  else
    // raise an exception
    inherited Assign (pt);
end;

//initialization
//RegisterClass (TWrapper);
end.

unit PersForm;

interface

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

type
  TForm1 = class(TForm)
    Panel1: TPanel;
    Label1: TLabel;
    Edit1: TEdit;
    SpeedButtonLoad: TSpeedButton;
    SpeedButtonSave: TSpeedButton;
    OpenDialog1: TOpenDialog;
    SaveDialog1: TSaveDialog;
    procedure FormCreate(Sender: TObject);
    procedure SpeedButtonSaveClick(Sender: TObject);
    procedure SpeedButtonLoadClick(Sender: TObject);
    procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormDestroy(Sender: TObject);
    procedure FormPaint(Sender: TObject);
  private
    PtList: TCollection;
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

uses
  DelphiPt;

procedure TForm1.FormCreate(Sender: TObject);
begin
  PtList := TCollection.Create (TDDHPoint);
end;

procedure TForm1.SpeedButtonSaveClick(Sender: TObject);
var
  Str1: TFileStream;
  Wrap: TWrapper;
begin
  if SaveDialog1.Execute then
  begin
    Str1 := TFileStream.Create (SaveDialog1.FileName,
      fmOpenWrite or fmCreate);
    try
      Wrap := TWrapper.Create (self);
      try
        Wrap.MyColl.Assign (ptList);
        Str1.WriteComponent (Wrap);
      finally
        Wrap.Free;
      end;
    finally
      Str1.Free;
    end;
  end;
end;

procedure TForm1.SpeedButtonLoadClick(Sender: TObject);
var
  Str1: TFileStream;
  Wrap: TWrapper;
begin
  if OpenDialog1.Execute then
  begin
    Str1 := TFileStream.Create (
      OpenDialog1.Filename, fmOpenRead);
    try
      Wrap := TWrapper.Create (self);
      try
        Wrap := Str1.ReadComponent (Wrap) as TWrapper;
        ptList.Assign (Wrap.MyColl);
      finally
        Wrap.Free;
      end;
    finally
      Str1.Free;
      Invalidate;
      Edit1.Text := 'Point ' + IntToStr (PtList.Count + 1);
    end;
  end;
end;

procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
var
  Pt: TDDHPoint;
begin
  Pt := PtList.Add as TDDHPoint;
  Pt.X := X;
  Pt.Y := Y;
  Pt.Text := Edit1.Text;
  Edit1.Text := 'Point ' + IntToStr (PtList.Count + 1);
  Invalidate;
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  // empty and destroy the list
  PtList.Clear;
  PtList.Free;
end;

procedure TForm1.FormPaint(Sender: TObject);
var
  I: Integer;
begin
  for I := 0 to PtList.Count - 1 do
    TDDHPoint (PtList.Items [I]).Paint (Canvas);
end;

end.