feat: resolve #7975, allow only one instance of the gui

src/apps/deskflow-gui/MainWindow.cpp

@@ -43,6 +43,8 @@
 #include <QApplication>
 #include <QDesktopServices>
 #include <QFileDialog>
+#include <QLocalServer>
+#include <QLocalSocket>
 #include <QMenu>
 #include <QMenuBar>
 #include <QMessageBox>
@@ -81,6 +83,7 @@ MainWindow::MainWindow(ConfigScopes &configScopes, AppConfig &appConfig)
       m_ClientConnection(this, appConfig),
       m_TlsUtility(appConfig),
       m_WindowSaveTimer(this),
+      m_guiDupeChecker{new QLocalServer(this)},
       m_actionAbout{new QAction(this)},
       m_actionClearSettings{new QAction(tr("Clear settings"), this)},
       m_actionHelp{new QAction(tr("Report a Bug"), this)},
@@ -119,6 +122,11 @@ MainWindow::MainWindow(ConfigScopes &configScopes, AppConfig &appConfig)
 
   toggleLogVisible(m_AppConfig.logExpanded());
 
+  // Setup the Instance Checking
+  // In case of a previous crash remove first
+  m_guiDupeChecker->removeServer(m_guiSocketName);
+  m_guiDupeChecker->listen(m_guiSocketName);
+
   createMenuBar();
   setupControls();
   connectSlots();
@@ -138,6 +146,7 @@ MainWindow::MainWindow(ConfigScopes &configScopes, AppConfig &appConfig)
 
 MainWindow::~MainWindow()
 {
+  m_guiDupeChecker->close();
   m_CoreProcess.cleanup();
 }
 
@@ -309,6 +318,8 @@ void MainWindow::connectSlots()
   connect(ui->rbModeClient, &QRadioButton::clicked, this, &MainWindow::setModeClient);
 
   connect(ui->btnToggleLog, &QAbstractButton::toggled, this, &MainWindow::toggleLogVisible);
+
+  connect(m_guiDupeChecker, &QLocalServer::newConnection, this, &MainWindow::showAndActivate);
 }
 
 void MainWindow::toggleLogVisible(bool visible)

src/apps/deskflow-gui/MainWindow.h

@@ -55,6 +55,7 @@ class QCheckBox;
 class QRadioButton;
 class QMessageBox;
 class QAbstractButton;
+class QLocalServer;
 
 class DeskflowApplication;
 class SetupWizard;
@@ -210,6 +211,9 @@ private:
   QTimer m_WindowSaveTimer;
   QSize m_expandedSize = QSize();
 
+  QLocalServer *m_guiDupeChecker = nullptr;
+  inline static const auto m_guiSocketName = QStringLiteral("deskflow-gui");
+
   // Window Actions
   QAction *m_actionAbout = nullptr;
   QAction *m_actionClearSettings = nullptr;

src/apps/deskflow-gui/main.cpp

@@ -35,8 +35,10 @@
 #include <QApplication>
 #include <QDebug>
 #include <QGuiApplication>
+#include <QLocalSocket>
 #include <QMessageBox>
 #include <QObject>
+#include <QSharedMemory>
 #include <QtGlobal>
 
 #if defined(Q_OS_MAC)
@@ -90,6 +92,29 @@ int main(int argc, char *argv[])
 
   QApplication app(argc, argv);
 
+  // Create a shared memory segment with a unique key
+  // This is to prevent a new instance from running if one is already running
+  QSharedMemory sharedMemory("deskflow-gui");
+
+  // Attempt to attach first and detach in order to clean up stale shm chunks
+  // This can happen if the previous instance was killed or crashed
+  if (sharedMemory.attach())
+    sharedMemory.detach();
+
+  // If we can create 1 byte of SHM we are the only instance
+  if (!sharedMemory.create(1)) {
+    // Ping the running instance to have it show itself
+    QLocalSocket socket;
+    socket.connectToServer("deskflow-gui", QLocalSocket::ReadOnly);
+    if (!socket.waitForConnected()) {
+      // If we can't connect to the other instance tell the user its running.
+      // This should never happen but just incase we should show something
+      QMessageBox::information(nullptr, QObject::tr("Deskflow"), QObject::tr("Deskflow is already running"));
+    }
+    socket.disconnectFromServer();
+    return 0;
+  }
+
 #if !defined(Q_OS_MAC)
   // causes dark mode to be used on some DE's
   if (qEnvironmentVariable("XDG_CURRENT_DESKTOP") != QLatin1String("KDE")) {