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Fix race condition allowing to run several instances of qBittorrent at the same time
This commit is contained in:
Christophe Dumez
351
src/qtsingleapp/qtsingleapplication.cpp
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351
src/qtsingleapp/qtsingleapplication.cpp
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/****************************************************************************
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**
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** Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
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** All rights reserved.
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** Contact: Nokia Corporation (qt-info@nokia.com)
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**
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** This file is part of a Qt Solutions component.
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**
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** Commercial Usage
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** Licensees holding valid Qt Commercial licenses may use this file in
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** accordance with the Qt Solutions Commercial License Agreement provided
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** with the Software or, alternatively, in accordance with the terms
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** contained in a written agreement between you and Nokia.
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**
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** GNU Lesser General Public License Usage
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** Alternatively, this file may be used under the terms of the GNU Lesser
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** General Public License version 2.1 as published by the Free Software
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** Foundation and appearing in the file LICENSE.LGPL included in the
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** packaging of this file. Please review the following information to
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** ensure the GNU Lesser General Public License version 2.1 requirements
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** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
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**
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** In addition, as a special exception, Nokia gives you certain
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** additional rights. These rights are described in the Nokia Qt LGPL
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** Exception version 1.1, included in the file LGPL_EXCEPTION.txt in this
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** package.
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**
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** GNU General Public License Usage
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** Alternatively, this file may be used under the terms of the GNU
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** General Public License version 3.0 as published by the Free Software
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** Foundation and appearing in the file LICENSE.GPL included in the
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** packaging of this file. Please review the following information to
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** ensure the GNU General Public License version 3.0 requirements will be
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** met: http://www.gnu.org/copyleft/gpl.html.
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**
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** Please note Third Party Software included with Qt Solutions may impose
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** additional restrictions and it is the user's responsibility to ensure
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** that they have met the licensing requirements of the GPL, LGPL, or Qt
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** Solutions Commercial license and the relevant license of the Third
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** Party Software they are using.
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**
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** If you are unsure which license is appropriate for your use, please
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** contact Nokia at qt-info@nokia.com.
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**
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****************************************************************************/
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#include "qtsingleapplication.h"
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#include "qtlocalpeer.h"
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#include <QtGui/QWidget>
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/*!
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\class QtSingleApplication qtsingleapplication.h
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\brief The QtSingleApplication class provides an API to detect and
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communicate with running instances of an application.
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This class allows you to create applications where only one
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instance should be running at a time. I.e., if the user tries to
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launch another instance, the already running instance will be
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activated instead. Another usecase is a client-server system,
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where the first started instance will assume the role of server,
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and the later instances will act as clients of that server.
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By default, the full path of the executable file is used to
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determine whether two processes are instances of the same
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application. You can also provide an explicit identifier string
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that will be compared instead.
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The application should create the QtSingleApplication object early
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in the startup phase, and call isRunning() or sendMessage() to
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find out if another instance of this application is already
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running. Startup parameters (e.g. the name of the file the user
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wanted this new instance to open) can be passed to the running
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instance in the sendMessage() function.
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If isRunning() or sendMessage() returns false, it means that no
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other instance is running, and this instance has assumed the role
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as the running instance. The application should continue with the
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initialization of the application user interface before entering
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the event loop with exec(), as normal. The messageReceived()
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signal will be emitted when the application receives messages from
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another instance of the same application.
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If isRunning() or sendMessage() returns true, another instance is
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already running, and the application should terminate or enter
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client mode.
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If a message is received it might be helpful to the user to raise
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the application so that it becomes visible. To facilitate this,
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QtSingleApplication provides the setActivationWindow() function
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and the activateWindow() slot.
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Here's an example that shows how to convert an existing
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application to use QtSingleApplication. It is very simple and does
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not make use of all QtSingleApplication's functionality (see the
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examples for that).
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\code
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// Original
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int main(int argc, char **argv)
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{
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QApplication app(argc, argv);
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MyMainWidget mmw;
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mmw.show();
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return app.exec();
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}
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// Single instance
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int main(int argc, char **argv)
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{
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QtSingleApplication app(argc, argv);
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if (app.isRunning())
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return 0;
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MyMainWidget mmw;
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app.setActivationWindow(&mmw);
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mmw.show();
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return app.exec();
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}
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\endcode
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Once this QtSingleApplication instance is destroyed(for example,
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when the user quits), when the user next attempts to run the
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application this instance will not, of course, be encountered. The
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next instance to call isRunning() or sendMessage() will assume the
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role as the new running instance.
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For console (non-GUI) applications, QtSingleCoreApplication may be
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used instead of this class, to avoid the dependency on the QtGui
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library.
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\sa QtSingleCoreApplication
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*/
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void QtSingleApplication::sysInit(const QString &appId)
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{
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actWin = 0;
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peer = new QtLocalPeer(this, appId);
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connect(peer, SIGNAL(messageReceived(const QString&)), SIGNAL(messageReceived(const QString&)));
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}
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/*!
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Creates a QtSingleApplication object. The application identifier
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will be QCoreApplication::applicationFilePath(). \a argc, \a
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argv, and \a GUIenabled are passed on to the QAppliation constructor.
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If you are creating a console application (i.e. setting \a
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GUIenabled to false), you may consider using
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QtSingleCoreApplication instead.
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*/
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QtSingleApplication::QtSingleApplication(int &argc, char **argv, bool GUIenabled)
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: QApplication(argc, argv, GUIenabled)
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{
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sysInit();
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}
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/*!
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Creates a QtSingleApplication object with the application
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identifier \a appId. \a argc and \a argv are passed on to the
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QAppliation constructor.
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*/
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QtSingleApplication::QtSingleApplication(const QString &appId, int &argc, char **argv)
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: QApplication(argc, argv)
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{
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sysInit(appId);
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}
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/*!
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Creates a QtSingleApplication object. The application identifier
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will be QCoreApplication::applicationFilePath(). \a argc, \a
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argv, and \a type are passed on to the QAppliation constructor.
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*/
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QtSingleApplication::QtSingleApplication(int &argc, char **argv, Type type)
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: QApplication(argc, argv, type)
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{
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sysInit();
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}
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#if defined(Q_WS_X11)
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/*!
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Special constructor for X11, ref. the documentation of
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QApplication's corresponding constructor. The application identifier
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will be QCoreApplication::applicationFilePath(). \a dpy, \a visual,
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and \a cmap are passed on to the QApplication constructor.
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*/
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QtSingleApplication::QtSingleApplication(Display* dpy, Qt::HANDLE visual, Qt::HANDLE cmap)
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: QApplication(dpy, visual, cmap)
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{
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sysInit();
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}
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/*!
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Special constructor for X11, ref. the documentation of
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QApplication's corresponding constructor. The application identifier
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will be QCoreApplication::applicationFilePath(). \a dpy, \a argc, \a
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argv, \a visual, and \a cmap are passed on to the QApplication
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constructor.
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*/
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QtSingleApplication::QtSingleApplication(Display *dpy, int &argc, char **argv, Qt::HANDLE visual, Qt::HANDLE cmap)
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: QApplication(dpy, argc, argv, visual, cmap)
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{
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sysInit();
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}
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/*!
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Special constructor for X11, ref. the documentation of
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QApplication's corresponding constructor. The application identifier
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will be \a appId. \a dpy, \a argc, \a
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argv, \a visual, and \a cmap are passed on to the QApplication
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constructor.
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*/
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QtSingleApplication::QtSingleApplication(Display* dpy, const QString &appId, int argc, char **argv, Qt::HANDLE visual, Qt::HANDLE cmap)
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: QApplication(dpy, argc, argv, visual, cmap)
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{
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sysInit(appId);
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}
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#endif
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/*!
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Returns true if another instance of this application is running;
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otherwise false.
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This function does not find instances of this application that are
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being run by a different user (on Windows: that are running in
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another session).
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\sa sendMessage()
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*/
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bool QtSingleApplication::isRunning()
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{
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return peer->isClient();
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}
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/*!
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Tries to send the text \a message to the currently running
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instance. The QtSingleApplication object in the running instance
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will emit the messageReceived() signal when it receives the
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message.
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This function returns true if the message has been sent to, and
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processed by, the current instance. If there is no instance
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currently running, or if the running instance fails to process the
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message within \a timeout milliseconds, this function return false.
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\sa isRunning(), messageReceived()
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*/
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bool QtSingleApplication::sendMessage(const QString &message, int timeout)
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{
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return peer->sendMessage(message, timeout);
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}
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/*!
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Returns the application identifier. Two processes with the same
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identifier will be regarded as instances of the same application.
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*/
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QString QtSingleApplication::id() const
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{
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return peer->applicationId();
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}
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/*!
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Sets the activation window of this application to \a aw. The
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activation window is the widget that will be activated by
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activateWindow(). This is typically the application's main window.
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If \a activateOnMessage is true (the default), the window will be
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activated automatically every time a message is received, just prior
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to the messageReceived() signal being emitted.
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\sa activateWindow(), messageReceived()
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*/
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void QtSingleApplication::setActivationWindow(QWidget* aw, bool activateOnMessage)
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{
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actWin = aw;
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if (activateOnMessage)
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connect(peer, SIGNAL(messageReceived(const QString&)), this, SLOT(activateWindow()));
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else
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disconnect(peer, SIGNAL(messageReceived(const QString&)), this, SLOT(activateWindow()));
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}
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/*!
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Returns the applications activation window if one has been set by
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calling setActivationWindow(), otherwise returns 0.
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\sa setActivationWindow()
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*/
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QWidget* QtSingleApplication::activationWindow() const
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{
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return actWin;
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}
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/*!
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De-minimizes, raises, and activates this application's activation window.
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This function does nothing if no activation window has been set.
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This is a convenience function to show the user that this
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application instance has been activated when he has tried to start
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another instance.
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This function should typically be called in response to the
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messageReceived() signal. By default, that will happen
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automatically, if an activation window has been set.
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\sa setActivationWindow(), messageReceived(), initialize()
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*/
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void QtSingleApplication::activateWindow()
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{
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if (actWin) {
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actWin->setWindowState(actWin->windowState() & ~Qt::WindowMinimized);
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actWin->raise();
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actWin->activateWindow();
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}
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}
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/*!
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\fn void QtSingleApplication::messageReceived(const QString& message)
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This signal is emitted when the current instance receives a \a
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message from another instance of this application.
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\sa sendMessage(), setActivationWindow(), activateWindow()
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*/
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/*!
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\fn void QtSingleApplication::initialize(bool dummy = true)
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\obsolete
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*/
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