var
Form1: TForm1;
OX,OY:Integer;
First:Boolean;
implementation
{$R *.DFM}
procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
Y: Integer);
begin
IF not First then Canvas.rectangle(ox,oy,ox+100,oy+100);
Canvas.Rectangle(X,Y,X+100,Y+100);
OX:=X;OY:=Y;
First:=False;
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
with Canvas do
Begin
Pen.mode:=pmXor;
Pen.color:=clwhite;
pen.Style:=psDot;
Brush.Color:=Clblack;
end;
First:=True;
End;