unitasd1.pas

罗小平<<delphi精要>>一书源码

unit Unitasd1;

interface

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

type
  TEEEE = class(TForm)
    Button1: TButton;
    procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
  private
    FromPoint, ToPoint: TPoint;
  public
    { Public declarations }
  end;

var
  EEEE: TEEEE;

implementation

{$R *.dfm}

procedure TEEEE.FormMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  FromPoint := Point(X, Y);
end;

procedure TEEEE.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
  if ssLeft in Shift then with Canvas do
  begin
    ToPoint := Point(X, Y);
    Repaint;
    Rectangle(FromPoint.X, FromPoint.Y, ToPoint.X, ToPoint.Y);
  end;
end;

end.