Clipboard Fehler

[napstar]

kann mir jemand erklähren was in diesem code hier gemacht wird.. ich will nicht einfach was übernehmen, ohne das ich was dabei lerne ^^

Delphi-Quellcode:

TfMain = class(TForm)
  private
    hNextViewer: DWORD;
  protected
    procedure WMChangeCBChain(var Msg: TMessage); message WM_CHANGECBCHAIN;
    procedure WMDrawClipboard(var Msg: TMessage); message WM_DRAWCLIPBOARD;
  end;


  // FormCreate:
  hNextViewer := SetClipBoardViewer(Handle);

  // FormDestroy:
  ChangeClipBoardChain(Handle, hNextViewer);


procedure TfMain.WMChangeCBChain(var Msg: TMessage);
begin
  if Msg.WParam = hNextViewer then
    hNextViewer := Msg.lParam
  else if hNextViewer <> 0 then
    SendMessage(hNextViewer, MSG.Msg, MSG.wParam, MSG.lParam);
end;

procedure TfMain.WMDrawClipboard(var Msg: TMessage);
var
  hClipbrdObj: THandle;
  pClipbrdObj: Pointer;
begin
  OpenClipboard(Handle);
  hClipbrdObj := GetClipboardData(CF_TEXT);
  if hClipbrdObj <> 0 then
    begin
      pClipbrdObj := GlobalLock(hClipbrdObj);
      if chk1.Checked then
        ClipboardChanged(PChar(pClipbrdObj));
    end;
  GlobalUnlock(DWORD(pClipbrdObj));
  GlobalFree(hClipbrdObj);
  CloseClipBoard;
end;