unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormPaint(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}
uses GDIPAPI,GDIPOBJ;
var
  x:Integer=20;
  y:Integer=20;
  w:Integer=100;
  h:Integer=50;
  f:Byte;
  a,b:Integer;
  p:TGPPen;
procedure TForm1.FormCreate(Sender: TObject);
begin
  p:=TGPPen.Create(aclRed,2);
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  p.Free;
end;

procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  f:=1;
  a:=x;
  b:=y;
end;

procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
  if  (f=0) then Exit;       {如果F为0,立即从当前的语句块中退出(注意：并不是退出程序)}
  if ssctrl in Shift then
  begin
    f:=2;
    Text:='ctrl键被按下,鼠标可调整大小';
  end else Text:='没有按下 Ctrl,鼠标可调整位置';

  a:=x - a;
  b:=y - b;
  Repaint;     {重绘}
  a:=x;
  b:=y;

end;

procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  f:=0;
end;

procedure TForm1.FormPaint(Sender: TObject);
var
  g:TGPGraphics;
begin
  g:=TGPGraphics.Create(Canvas.Handle);
  g.Clear(aclWhite);
  case f of
    1: begin
      inc(x,a);   {相当于x:=x + a}
      inc(y,b);   {相当于y:=y + b}
    end;
    2: begin
      inc(w,a);   {相当于w:=w + a}
      inc(h,b);   {相当于h:=h + b}
    end;
  end;
  g.DrawEllipse(p,x,y,w,h);     {画一个椭圆}
  g.Free;

end;

end.