keepassx · VukoDrakkeinen · Jul 25, 2016
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -149,6 +149,7 @@ if(WITH_TESTS)
 endif(WITH_TESTS)
 
 find_package(Qt5Core          5.2 REQUIRED)
+find_package(Qt5Network       5.2 REQUIRED)
 find_package(Qt5Concurrent    5.2 REQUIRED)
 find_package(Qt5Widgets       5.2 REQUIRED)
 find_package(Qt5Test          5.2 REQUIRED)

diff --git a/README.md b/README.md
@@ -50,7 +50,7 @@ The following tools must exist within your PATH:
 
 * make
 * cmake (>= 2.8.12)
-* g++ (>= 4.7) or clang++ (>= 3.0)
+* g++ (>= 4.7) or clang++ (>= 3.1)
 
 The following libraries are required:
 

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
@@ -163,12 +163,13 @@ qt5_wrap_ui(keepassx_SOURCES ${keepassx_FORMS})
 
 add_library(keepassx_core STATIC ${keepassx_SOURCES})
 set_target_properties(keepassx_core PROPERTIES COMPILE_DEFINITIONS KEEPASSX_BUILDING_CORE)
-target_link_libraries(keepassx_core Qt5::Core Qt5::Concurrent Qt5::Widgets)
+target_link_libraries(keepassx_core Qt5::Core Qt5::Network Qt5::Concurrent Qt5::Widgets)
 
 add_executable(${PROGNAME} WIN32 MACOSX_BUNDLE ${keepassx_SOURCES_MAINEXE})
 target_link_libraries(${PROGNAME}
                       keepassx_core
                       Qt5::Core
+                      Qt5::Network
                       Qt5::Concurrent
                       Qt5::Widgets
                       ${GCRYPT_LIBRARIES}

diff --git a/src/gui/Application.cpp b/src/gui/Application.cpp
@@ -20,6 +20,9 @@
 
 #include <QAbstractNativeEventFilter>
 #include <QFileOpenEvent>
+#include <QLockFile>
+#include <QStandardPaths>
+#include <QtNetwork/QLocalSocket>
 
 #include "autotype/AutoType.h"
 
@@ -46,10 +49,64 @@ class XcbEventFilter : public QAbstractNativeEventFilter
 Application::Application(int& argc, char** argv)
     : QApplication(argc, argv)
     , m_mainWindow(nullptr)
+    , alreadyRunning(false)
+    , lock(nullptr)
 {
 #if defined(Q_OS_UNIX) && !defined(Q_OS_OSX)
     installNativeEventFilter(new XcbEventFilter());
 #endif
+
+    QString userName = qgetenv("USER");
+    if (userName.isEmpty()) {
+        userName = qgetenv("USERNAME");
+    }
+    QString identifier = "keepassx2";
+    if (!userName.isEmpty()) {
+        identifier.append("-");
+        identifier.append(userName);
+    }
+    QString socketName = identifier + ".socket";
+    QString lockName = identifier + ".lock";
+
+    // According to documentation we should use RuntimeLocation on *nixes, but even Qt doesn't respect
+    // this and creates sockets in TempLocation, so let's be consistent.
+    lock = new QLockFile(QStandardPaths::writableLocation(QStandardPaths::TempLocation) + "/" + lockName);
+    lock->setStaleLockTime(0);
+    lock->tryLock();
+    switch (lock->error()) {
+    case QLockFile::NoError:
+        server.setSocketOptions(QLocalServer::UserAccessOption);
+        server.listen(socketName);
+        connect(&server, SIGNAL(newConnection()), this, SIGNAL(anotherInstanceStarted()));
+        break;
+    case QLockFile::LockFailedError: {
+        alreadyRunning = true;
+        // notify the other instance
+        // try several times, in case the other instance is still starting up
+        QLocalSocket client;
+        for (int i = 0; i < 3; i++) {
+            client.connectToServer(socketName);
+            if (client.waitForConnected(150)) {
+                client.abort();
+                break;
+            }
+        }
+        break;
+    }
+    default:
+        qWarning() << QCoreApplication::translate("Main",
+                                                  "The lock file could not be created. Single-instance mode disabled.")
+                      .toUtf8().constData();
+    }
+}
+
+Application::~Application()
+{
+    server.close();
+    if (lock) {
+        lock->unlock();
+        delete lock;
+    }
 }
 
 void Application::setMainWindow(QWidget* mainWindow)
@@ -77,3 +134,8 @@ bool Application::event(QEvent* event)
 
     return QApplication::event(event);
 }
+
+bool Application::isAlreadyRunning() const
+{
+    return alreadyRunning;
+}
diff --git a/src/gui/Application.h b/src/gui/Application.h
@@ -20,22 +20,30 @@
 #define KEEPASSX_APPLICATION_H
 
 #include <QApplication>
+#include <QtNetwork/QLocalServer>
+class QLockFile;
 
 class Application : public QApplication
 {
     Q_OBJECT
 
 public:
     Application(int& argc, char** argv);
+    ~Application();
     void setMainWindow(QWidget* mainWindow);
 
     bool event(QEvent* event) override;
+    bool isAlreadyRunning() const;
 
 Q_SIGNALS:
     void openFile(const QString& filename);
+    void anotherInstanceStarted();
 
 private:
     QWidget* m_mainWindow;
+    bool alreadyRunning;
+    QLockFile* lock;
+    QLocalServer server;
 };
 
 #endif // KEEPASSX_APPLICATION_H
diff --git a/src/main.cpp b/src/main.cpp
@@ -40,6 +40,11 @@ int main(int argc, char** argv)
     // don't set organizationName as that changes the return value of
     // QStandardPaths::writableLocation(QDesktopServices::DataLocation)
 
+    if (app.isAlreadyRunning()) {
+        qWarning() << QCoreApplication::translate("Main", "Another instance of KeePassX 2 is already running.").toUtf8().constData();
+        return 0;
+    }
+
     QApplication::setQuitOnLastWindowClosed(false);
 
     if (!Crypto::init()) {
@@ -85,6 +90,14 @@ int main(int argc, char** argv)
     mainWindow.show();
     app.setMainWindow(&mainWindow);
 
+    QObject::connect(&app, &Application::anotherInstanceStarted,
+                    [&]() {
+                        mainWindow.ensurePolished();
+                        mainWindow.setWindowState(mainWindow.windowState() & ~Qt::WindowMinimized);
+                        mainWindow.show();
+                        mainWindow.raise();
+                        mainWindow.activateWindow();
+                    });
     QObject::connect(&app, SIGNAL(openFile(QString)), &mainWindow, SLOT(openDatabase(QString)));
 
     if (!args.isEmpty()) {