进程间传递消息（发送和接收系统消息）

{
  2002.07.22
  关于如何发送和接收系统消息
  作者：王珍义
  nickname:LargeWang(老王)
  QQ: 33728007
  欢迎光临鹏业软件 www.pengesoft.com.cn

  以下代码Delphi7.0通过，编译后启动两个进程，然后在一个窗口中点击Button1试试。
}

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    Msg: LongInt;
    { Private declarations }
  protected
    procedure WndProc(var Message: TMessage); override;
  public

    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
begin
  Msg := RegisterWindowMessage('wm_mymessage');
  Self.BringToFront;
end;

procedure TForm1.WndProc(var Message: TMessage);
begin
  if Message.Msg = Msg then begin
    Caption := '';
    ShowMessage('收到消息了');
  end
  else begin
    inherited;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  M: TMessage;
  B: DWord;
begin
  M.Msg := Msg;
  B := BSM_ALLCOMPONENTS;
  BroadcastSystemMessage(BSF_POSTMESSAGE, @B , M.Msg, M.WParam, M.LParam );
end;

end.

////窗口文件
object Form1: TForm1
  Left = 192
  Top = 107
  Width = 696
  Height = 480
  Caption = 'Form1'
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'MS Sans Serif'
  Font.Style = []
  OldCreateOrder = False
  OnCreate = FormCreate
  PixelsPerInch = 96
  TextHeight = 13
  object Button1: TButton
    Left = 204
    Top = 84
    Width = 75
    Height = 25
    Caption = 'Button1'
    TabOrder = 0
    OnClick = Button1Click
  end
end