[Zmeo]

Примерный код создания прямоугольника и окружности.

Код:

unit Unit1;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs;
 
type
  TForm1 = class(TForm)
    procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
  x1, y1: integer;
  Down: BOOL;
implementation
 
{$R *.dfm}
 
procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  Down := True;
  x1 := x;
  y1 := y;
end;
 
procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  Down := False;
end;
 
procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
  if Down then
  begin
    if ssShift in Shift then
    begin
      Form1.Repaint;
      Canvas.Rectangle(x1,y1,x,y);
    end else
      begin
        Form1.Repaint;
        Canvas.Ellipse(x1,y1,x,y);
      end;
  end;
end;
 
end.