# class KUniqueApplication

###

Module | kdeui
Namespace |
Class | KUniqueApplication
Inherits | KApplication

KUniqueApplication is a KApplication which only uses a single process. When a KUniqueApplication is started, it attempts to contact an existing copy of the application. If successful, the program asks the existing process to create a new instance by calling its newInstance() method and then exits. If there is no existing process then the program forks and calls the newInstance() method. When newInstance() is called, the application will typically create a new window or activate an existing one.

Instances of KUniqueApplication can be made to behave like a normal application by passing the StartFlag.NonUniqueInstance flag to start().

Please note that this supports only one process per KDE session. If your application can only be opened once per user or once per host, you need to ensure this independently of KUniqueApplication.

The .desktop file for the application should state X-DBUS-StartupType=Unique, see ktoolinvocation.h

If your application is used to open files, it should also support the --tempfile option (see KCmdLineArgs.addTempFileOption()), to delete tempfiles after use. Add X-KDE-HasTempFileOption=true to the .desktop file to indicate this.

See also KApplication Author Preston Brown <pbrown@kde.org>

### enums

- StartFlag { NonUniqueInstance }
  typesafe object: StartFlags

enum details

### methods

- KUniqueApplication (GUIenabled, configUnique)

  returns ctor
  KDE 4.1.0 and later only

  Argument | Type | Default
  --- | --- | ---
  GUIenabled | bool | 1
  configUnique | bool | 0

  Constructor. Takes command line arguments from KCmdLineArgs

  GUIenabled - Set to false to disable all GUI stuff. This implies no styles either.

  configUnique - If true, the uniqueness of the application will depend on the value of the "MultipleInstances" key in the "KDE" group of the application config file.

- KUniqueApplication (display, visual, colormap, configUnique)

  returns ctor
  KDE 4.1.0 and later only

  Argument | Type | Default
  --- | --- | ---
  display | Display |
  visual | Qt.HANDLE | 0
  colormap | Qt.HANDLE | 0
  configUnique | bool | 0

  Constructor. Takes command line arguments from KCmdLineArgs

  display - Will be passed to Qt as the X display. The display must be valid and already opened.

  visual - Pointer to the X11 visual that should be used by the application. If NULL, the default visual will be used instead.

  colormap - The colormap that should be used by the application. If 0, the default colormap will be used instead.

  configUnique - If true, the uniqueness of the application will depend on the value of the "MultipleInstances" key in the "KDE" group of the application config file.

- KUniqueApplication (a0, a1)

  returns ctor
  before KDE 4.1.0 only

  Argument | Type | Default
  --- | --- | ---
  a0 | bool | 1
  a1 | bool | 0

- KUniqueApplication (a0, a1, a2, a3)

  returns ctor
  before KDE 4.1.0 only

  Argument | Type | Default
  --- | --- | ---
  a0 | Display |
  a1 | Qt.HANDLE | 0
  a2 | Qt.HANDLE | 0
  a3 | bool | 0

- addCmdLineOptions ( )

  returns Nothing
  static

  Adds command line options specific for KUniqueApplication.

  Should be called before calling KUniqueApplication constructor and / or start().

- newInstance ( )

  returns int

  Creates a new "instance" of the application.

  Usually this will involve making some calls into the GUI portion of your application asking for a new window to be created, possibly with some data already loaded based on the arguments received.

  Command line arguments have been passed to KCmdLineArgs before this function is called and can be checked in the usual way.

  The default implementation ensures the mainwindow of the already running instance is shown and activated if necessary. If your application has only one mainwindow, you should call this default implementation and only add your special handling if needed.

  Note that newInstance() is called also in the first started application process.

  For applications that share one process for several mainwindows, the reimplementation could be:

      int MyApp.newInstance()
      {
      KCmdLineArgs.setCwd(QDir.currentPath().toUtf8());
      KCmdLineArgs* args = KCmdLineArgs.parsedArgs();
      static bool first = true;
      if (args->count() > 0) {
      for (int i = 0; i < args->count(); ++i) {
      openWindow(args->url(i));
      }
      } else if( !first || !isSessionRestored()) {
      openWindow(KUrl()); // create a new window
      }
      first = false;
      args->clear();
      return 0;
      }

  Returns An exit value. The calling process will exit with this value.

- restoringSession ( )

  returns bool

  Returns whether newInstance() is being called while session restoration is in progress.

- setHandleAutoStarted ( )

  returns Nothing
  static

  Internal

- start (flags)

  returns bool
  static
  KDE 4.1.0 and later only

  Argument | Type | Default
  --- | --- | ---
  flags | KUniqueApplication.StartFlags |

  Forks and registers with D-Bus.

  The command line arguments are being sent via D-Bus to newInstance() and will be received once the application enters the event loop.

  Typically this is used like:

      int main(int argc, char **argv) {
      KAboutData about("myappname", 0, ki18n("myAppName"), .....);
      KCmdLineArgs.init(argc, argv, &about);
      KCmdLineArgs.addCmdLineOptions( myCmdOptions );
      KUniqueApplication.addCmdLineOptions();

      if (!KUniqueApplication.start()) {
      fprintf(stderr, "myAppName is already running!\n");
      return 0;
      }
      KUniqueApplication a;
      return a.exec();
      }

  Note that it's not necessary to call start() explicitly. It will be called automatically before creating KUniqueApplication if it hasn't been called yet, without any performance impact.

  Also note that you MUST call KUniqueApplication.addCmdLineOptions(), if you use command line options before start() is called.

  flags - Optional flags which control how a new instance of the application is started. Returns true if registration is successful. false if another process was already running.

- start ( )

  returns bool
  static

### enums - detail

- StartFlag { NonUniqueInstance }

  Create a new instance of the application in a new process and do not attempt to re-use an existing process.

  With this flag set, the new instance of the application will behave as if it were a plain KApplication rather than a KUniqueApplication.

  This is useful if you have an application where all instances are typically run in a single process but under certain circumstances new instances may require their own process.

  typesafe object: StartFlags

NonUniqueInstance - 0x1 -