scwndprc.pas

《Delphi开发人员指南》配书原码

unit Scwndprc;

interface

uses Forms, Messages;

const
  DDGM_FOOMSG = WM_USER;

implementation

uses Windows, SysUtils, Dialogs;

var
  WProc: Pointer;

function NewWndProc(Handle: hWnd; Msg, wParam, lParam: Longint): Longint;
  stdcall;
{ This is a Win32 API-level window procedure. It handles the messages }
{ received by the Application window. }
begin
  if Msg = DDGM_FOOMSG then
    { If it's our user-defined message, then alert the user. }
    ShowMessage(Format('Message seen by WndProc! Value is: $%x', [Msg]));
  { Pass message on to old window procedure }
  Result := CallWindowProc(WProc, Handle, Msg, wParam, lParam);
end;

initialization
  { Set window procedure of Application window. }
  WProc := Pointer(SetWindowLong(Application.Handle, gwl_WndProc,
    Integer(@NewWndProc)));
end.