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Как корректно определить изменения в оборудовании PlugNPlay?

Пример:

  type
    TForm1 = class(TForm)
      Button1: TButton;
    private
      { Private declarations }
      procedure WMDeviceChange(var Message: TMessage);
        message WM_DEVICECHANGE;
    public
      { Public declarations }
    end;

  var
    Form1: TForm1;

  implementation

  {$R *.DFM}

  const DBT_DEVICEARRIVAL = $8000;
  const DBT_DEVICEQUERYREMOVE = $8001;
  const DBT_DEVICEQUERYREMOVEFAILED = $8002;
  const DBT_DEVICEREMOVEPENDING = $8003;
  const DBT_DEVICEREMOVECOMPLETE = $8004;
  const DBT_DEVICETYPESPECIFIC = $8005;
  const DBT_CONFIGCHANGED = $0018;

  procedure TForm1.WMDeviceChange(var Message: TMessage);
  var
    s : string;
  begin
  {Do Something here}
    case Message.wParam of
      DBT_DEVICEARRIVAL :
        s := 'A device has been inserted and is now available';
      DBT_DEVICEQUERYREMOVE: begin
        s := 'Permission to remove a device is requested';
        ShowMessage(s);
       {True grants premission}
        Message.Result := integer(true);
        exit;
      end;
      DBT_DEVICEQUERYREMOVEFAILED :
        s := 'Request to remove a device has been canceled';
      DBT_DEVICEREMOVEPENDING :
        s := 'Device is about to be removed';
      DBT_DEVICEREMOVECOMPLETE :
        s := 'Device has been removed';
      DBT_DEVICETYPESPECIFIC :
        s := 'Device-specific event';
      DBT_CONFIGCHANGED :
        s:= 'Current configuration has changed'
      else s := 'Unknown Device Message';
    end;
    ShowMessage(s);
    inherited;
  end;

Источник: Дельфи. Вокруг да около.

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