/* This file is part of the KDE libraries
    Copyright (c) 1999 Preston Brown <pbrown@kde.org>
    Copyright (c) 2000-2001 Waldo Bastian <bastian@kde.org>

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public License
    along with this library; see the file COPYING.LIB.  If not, write to
    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
    Boston, MA 02110-1301, USA.
*/

#ifndef KUNIQUEAPP_H
#define KUNIQUEAPP_H

#include <kdelibs4support_export.h>
#include <kapplication.h>

/**
 * 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 you use command line options before start() is called, you MUST call addCmdLineOptions()
 * so that the KUniqueApplication-specific command-line options can still work.
 *
 * 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 KApplication
 * @author Preston Brown <pbrown@kde.org>
 */
class KDELIBS4SUPPORT_DEPRECATED_EXPORT KUniqueApplication : public KApplication
{
    Q_OBJECT
public:
    /**
     * Constructor. Takes command line arguments from KCmdLineArgs
     *
     * @param GUIenabled Set to false to disable all GUI stuff. This implies
     * no styles either.
     * @param 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.
     */
    KDELIBS4SUPPORT_DEPRECATED explicit KUniqueApplication(bool GUIenabled = true,
                                bool configUnique = false);

    /**
     * Adds command line options specific for KUniqueApplication.
     *
     * Should be called before calling KUniqueApplication constructor
     * and / or start().
     */
    static void addCmdLineOptions();

    /**
     * These flags can be used to specify how new instances of
     * unique applications are created.
     */
    enum StartFlag {
        /**
         * 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.
         */
        NonUniqueInstance = 0x1
    };
    Q_DECLARE_FLAGS(StartFlags, StartFlag)

    /**
     * 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:
     * \code
     * 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();
     * }
     * \endcode
     * 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.
     *
     * @param flags   Optional flags which control how a new instance
     *                of the application is started.
     * @return true if registration is successful.
     *         false if another process was already running.
     */
    static bool start(StartFlags flags);
    // BIC: merge with start(StartFlags flags = StartFlags())
    static bool start();

    /**
     * Destructor
     */
    ~KUniqueApplication() override;

    /**
     * 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:
     * \code
      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;
      }
     * \endcode
     *
     * @return An exit value. The calling process will exit with this value.
     */
    virtual int newInstance();

    /**
     * Returns whether newInstance() is being called while session
     * restoration is in progress.
     */
    bool restoringSession();

    /**
     * @internal
     */
#ifndef KDELIBS4SUPPORT_NO_DEPRECATED
    KDELIBS4SUPPORT_DEPRECATED static void setHandleAutoStarted();
#endif

private:
    friend class KUniqueApplicationAdaptor;
    class Private;
    Private *const d;

    Q_PRIVATE_SLOT(d, void _k_newInstanceNoFork())
};
Q_DECLARE_OPERATORS_FOR_FLAGS(KUniqueApplication::StartFlags)

#endif
