_EXAMINING DELPHI 2.0_
by Ted Faison

Listing One

TMyThread = class(TThread)
protected
    procedure Execute; override;
public
    constructor Create(your parameters} );
  end;



Listing Two

type
  TMyForm = class(TForm)
private
  LengthyOperation: TMyThread;
  end;


Listing Three

procedure TMyForm.StartButtonClick(Sender: TObject);
begin
  LengthyOperation:= TMyThread.Create( your parameter list);
end;


Listing Four

procedure TMyForm. AbortButtonClick(Sender: TObject);
begin
  LengthyOperation.Terminate;
end;


Listing Five

procedure TShape.Paint;
begin
  with Canvas do
        Rectangle(100, 100, 200, 200);
end;


Listing Six


procedure TMyForm.WndProc(var Message: TMessage);
begin
  case Message.Msg of
   WM_LBUTTONDOWN,  WM_CHAR:
      {do something}
      Exit;
  end;
  inherited;
end; 


Listing Seven

procedure TForm1.Button1Click(Sender: TObject);
begin

end;




Listing Eight

unit ThreadTest;
interface
uses
  Windows, Messages, SysUtils, Classes, Graphics, 
  Controls, Forms, Dialogs, ExtCtrls;
type
  TThreadBouncingObject = class(TThread)
  private
    ContainmentBox: TPaintBox;
    BoundsCheckBox: TRect;
    P: TPoint;
    XIncrement, YIncrement: Integer;
    procedure UpdateScreen;
  protected
    procedure Execute; override;
  public
    constructor Create(Box: TPaintBox);
  end;
const
  WIDTH = 10;
  HEIGHT = 10;
implementation

{$R *.DFM}

constructor TThreadBouncingObject.Create(Box: TPaintBox);
begin
  inherited Create(True);
  ContainmentBox := Box;
  BoundsCheckBox := Rect(0, 0, Box.Width - WIDTH, Box.Height - HEIGHT);
  P.X := Random(ContainmentBox.Width - WIDTH);
  P.Y := Random(ContainmentBox.Height - HEIGHT);
  XIncrement := 1;
  YIncrement := 1;
end;
procedure TThreadBouncingObject.Execute;
begin
  repeat
    begin
      {update the X position}
      P.X := P.X + XIncrement;
      if (XIncrement > 0) and (P.X >= BoundsCheckBox.Right) or
         (XIncrement < 0) and (P.X <= BoundsCheckBox.Left) then
        XIncrement := -XIncrement;
        
      {update the Y position}
      P.Y := P.Y + YIncrement;
      if (YIncrement > 0) and (P.Y >= BoundsCheckBox.Bottom) or
         (YIncrement < 0) and (P.Y <= BoundsCheckBox.Top) then
        YIncrement := -YIncrement;
      UpdateScreen;
      Sleep(10); {pause briefly}
    end
  until Terminated;
end;
procedure TThreadBouncingObject.UpdateScreen;
begin
    ContainmentBox.Canvas.Rectangle(P.X, P.Y, P.X + WIDTH, P.Y + HEIGHT);
end;

end.


Listing Nine

unit TestForm;
interface
uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  ExtCtrls, ThreadTest, StdCtrls;
type
  TForm3Threads = class(TForm)
    Panel1: TPanel;
    PaintBox1: TPaintBox;
    PaintBox2: TPaintBox;
    PaintBox3: TPaintBox;
    ButtonStart: TButton;
    ButtonStop: TButton;
    procedure FormDestroy(Sender: TObject);
    procedure ButtonStartClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure ButtonStopClick(Sender: TObject);
  private
    Object1: TThreadBouncingObject;
    Object2: TThreadBouncingObject;
    Object3: TThreadBouncingObject;
  public
    { Public declarations }
  end;
var
  Form3Threads: TForm3Threads;
implementation
{$R *.DFM}
procedure TForm3Threads.FormDestroy(Sender: TObject);
begin
  Object1.Terminate;
  Object1.Free;
  Object2.Terminate;
  Object2.Free;
  Object3.Terminate;
  Object3.Free;
end;
procedure TForm3Threads.ButtonStartClick(Sender: TObject);
begin
  Object1.Resume;
  Object2.Resume;
  Object3.Resume;
end;
procedure TForm3Threads.FormCreate(Sender: TObject);
begin
  Randomize;   {for the object initial positions}
  Object1 := TThreadBouncingObject.Create(PaintBox1);
  Object2 := TThreadBouncingObject.Create(PaintBox2);
  Object3 := TThreadBouncingObject.Create(PaintBox3);

end;
procedure TForm3Threads.ButtonStopClick(Sender: TObject);
begin
  Object1.Suspend;
  Object2.Suspend;
  Object3.Suspend;
end;
end.