feat: single instance check for StatusWindow

.gitignore

@@ -10,6 +10,7 @@ nimcache
 .idea
 *.orig
 doc
+cmake-build-*
 
 # libraries
 *.a

lib/include/DOtherSide/DOtherSideStatusWindow.h

@@ -4,6 +4,8 @@
 #include <QQuickWindow>
 #include <QScreen>
 
+class QLocalServer;
+
 class StatusWindow: public QQuickWindow
 {
     Q_OBJECT
@@ -13,6 +15,7 @@ class StatusWindow: public QQuickWindow
 public:
 
     explicit StatusWindow(QWindow *parent = nullptr);
+    ~StatusWindow();
 
     Q_INVOKABLE void toggleFullScreen();
 
@@ -27,14 +30,17 @@ public:
 
 signals:
     void isFullScreenChanged();
+    void secondInstanceDetected();
 
 private:
+    void checkSingleInstance();
     void removeTitleBar();
     void showTitleBar();
     void initCallbacks();
 
 private:
     bool m_isFullScreen;
+    QLocalServer *m_localServer;
 };
 
 #endif // STATUSWINDOW_H

lib/src/DOtherSideStatusWindow.cpp

@@ -1,9 +1,16 @@
 #include "DOtherSide/DOtherSideStatusWindow.h"
 
+#include <QLocalServer>
+#include <QLocalSocket>
+#include <QDir>
+#include <QCryptographicHash>
+
 StatusWindow::StatusWindow(QWindow *parent)
 : QQuickWindow(parent),
-  m_isFullScreen(false)
+  m_isFullScreen(false),
+  m_localServer(new QLocalServer(this))
 {
+    checkSingleInstance();
     removeTitleBar();
 
     connect(this, &QQuickWindow::windowStateChanged, [&](Qt::WindowState windowState) {
@@ -19,6 +26,13 @@ StatusWindow::StatusWindow(QWindow *parent)
     });
 }
 
+StatusWindow::~StatusWindow()
+{
+    if (m_localServer->isListening()) {
+        m_localServer->close();
+    }
+}
+
 void StatusWindow::toggleFullScreen()
 {
     if (m_isFullScreen) {
@@ -32,3 +46,28 @@ bool StatusWindow::isFullScreen() const
 {
 	return m_isFullScreen;
 }
+
+void StatusWindow::checkSingleInstance()
+{
+    const auto currentDir = QDir::currentPath();
+    auto socketName = QString(QCryptographicHash::hash(currentDir.toUtf8(), QCryptographicHash::Md5).toHex());
+
+#ifndef Q_OS_WIN
+    socketName = QString("/tmp/%1").arg(socketName);
+#endif
+
+    QLocalSocket localSocket;
+    localSocket.connectToServer(socketName);
+
+    // the first instance start will be delayed by this timeout (ms) to ensure there are no other instances.
+    // note: this is an ad-hoc timeout value selected based on prior experience.
+    const bool connected = localSocket.waitForConnected(100);
+    if (!connected) {
+        connect(m_localServer, &QLocalServer::newConnection, this, &StatusWindow::secondInstanceDetected);
+        if (!m_localServer->listen(socketName)) {
+            qWarning() << "QLocalServer::listen(" << socketName << ") failed";
+        }
+    } else {
+        qFatal("Terminating app as the second running instance...");
+    }
+}