//声明:MoveToEx(  DC: HDC;         {设备环境句柄}  p2, p3: Integer; {坐标}  p4: PPoint       {用于保存 p2、p3 值的 TPoint 结构的指针}): BOOL;LineTo(  DC: HDC;      {设备环境句柄}  X, Y: Integer {直线终点坐标}): BOOL;         //举例:unit Unit1;interfaceuses  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,  Dialogs, StdCtrls;type  TForm1 = class(TForm)    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);  end;var  Form1: TForm1;implementation{$R *.dfm}var  flag: Boolean;procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;  Shift: TShiftState; X, Y: Integer);begin  MoveToEx(Canvas.Handle, X, Y, nil);  flag := True;end;procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,  Y: Integer);begin  if flag then LineTo(Canvas.Handle, X, Y);end;procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;  Shift: TShiftState; X, Y: Integer);begin  flag := False;end;end.         //效果图: