unit Unit1;

{$mode objfpc}{$H+}

interface

uses

  Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs;

type

  { TForm1 }

  TForm1 = class(TForm)

    procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);

  private

    { private declarations }

  public

    { public declarations }

  end;

var

  Form1: TForm1;

  px: integer = 0;

  py: integer = 0;

implementation

{$R *.lfm}

procedure Line(x1, y1, x2, y2: integer);

var

  col, row: integer;

begin

  for col := -10 to 10 do begin

    for row := -10 to 10 do begin

      Form1.Canvas.MoveTo(x1 + col*200, y1 + row*200);

      Form1.Canvas.LineTo(x2 + col*200, y2 + row*200);

    end;

  end;

end;

procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,

  Y: Integer);

begin

  if ssRight in Shift then Form1.Refresh;

  if ssLeft in Shift then Line(px, py, x, y);

  px := x;

  py := y;

end;

end.