unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs;

type
TForm1 = class(TForm)
procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
private
Capturing : bool;
Captured : bool;
StartPlace : TPoint;
EndPlace : TPoint;
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

function MakeRect(Pt1 : TPoint;
Pt2 : TPoint) : TRect;
begin
if pt1.x < pt2.x then begin
Result.Left := pt1.x;
Result.Right := pt2.x;
end else begin
Result.Left := pt2.x;
Result.Right := pt1.x;
end;
if pt1.y < pt2.y then begin
Result.Top := pt1.y;
Result.Bottom := pt2.y;
end else begin
Result.Top := pt2.y;
Result.Bottom := pt1.y;
end;
end;

procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
begin
if Captured then
DrawFocusRect(Form1.Canvas.Handle,
MakeRect(StartPlace,
EndPlace));
StartPlace.x := X;
StartPlace.y := Y;
EndPlace.x := X;
EndPlace.y := Y;
DrawFocusRect(Form1.Canvas.Handle,
MakeRect(StartPlace,
EndPlace));
Capturing := true;
Captured := true;
end;

procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
Y: Integer);
begin
if Capturing then begin
DrawFocusRect(Form1.Canvas.Handle,
MakeRect(StartPlace,
EndPlace));
EndPlace.x := X;
EndPlace.y := Y;
DrawFocusRect(Form1.Canvas.Handle,
MakeRect(StartPlace,
EndPlace));
end;
end;

procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
begin
Capturing := false;
end;

end.