Fix Single Istance behavior

src/gui/Application.cpp

@@ -19,6 +19,7 @@
 
 #include "Application.h"
 #include "MainWindow.h"
+#include "core/Config.h"
 
 #include <QAbstractNativeEventFilter>
 #include <QFileOpenEvent>
@@ -100,6 +101,10 @@ Application::Application(int& argc, char** argv)
     if (!userName.isEmpty()) {
         identifier.append("-");
         identifier.append(userName);
+#ifdef QT_DEBUG
+        // In DEBUG mode don't interfere with Release instances 
+        identifier.append("-DEBUG");
+#endif
     }
     QString socketName = identifier + ".socket";
     QString lockName = identifier + ".lock";
@@ -119,12 +124,14 @@ Application::Application(int& argc, char** argv)
         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;
+        if (config()->get("SingleInstance").toBool()) {
+            QLocalSocket client;
+            for (int i = 0; i < 3; i++) {
+                client.connectToServer(socketName);
+                if (client.waitForConnected(150)) {
+                    client.abort();
+                    break;
+                }
             }
         }
         break;
@@ -232,6 +239,10 @@ void Application::quitBySignal()
 
 bool Application::isAlreadyRunning() const
 {
-    return alreadyRunning;
+#ifdef QT_DEBUG
+    // In DEBUG mode we can run unlimited instances
+    return false;
+#endif
+    return config()->get("SingleInstance").toBool() && alreadyRunning;
 }
 

src/gui/SettingsWidget.cpp

@@ -107,6 +107,10 @@ void SettingsWidget::loadSettings()
             tr("Access error for config file %1").arg(config()->getFileName()), MessageWidget::Error);
     }
 
+#ifdef QT_DEBUG
+    m_generalUi->singleInstanceCheckBox->setEnabled(false);
+#endif
+    m_generalUi->singleInstanceCheckBox->setChecked(config()->get("SingleInstance").toBool());
     m_generalUi->rememberLastDatabasesCheckBox->setChecked(config()->get("RememberLastDatabases").toBool());
     m_generalUi->rememberLastKeyFilesCheckBox->setChecked(config()->get("RememberLastKeyFiles").toBool());
     m_generalUi->openPreviousDatabasesOnStartupCheckBox->setChecked(
@@ -176,6 +180,7 @@ void SettingsWidget::saveSettings()
         return;
     }
 
+    config()->set("SingleInstance", m_generalUi->singleInstanceCheckBox->isChecked());
     config()->set("RememberLastDatabases", m_generalUi->rememberLastDatabasesCheckBox->isChecked());
     config()->set("RememberLastKeyFiles", m_generalUi->rememberLastKeyFilesCheckBox->isChecked());
     config()->set("OpenPreviousDatabasesOnStartup",

src/gui/SettingsWidgetGeneral.ui

@@ -33,6 +33,16 @@
        <string>Basic Settings</string>
       </attribute>
       <layout class="QVBoxLayout" name="verticalLayout">
+       <item>
+        <widget class="QCheckBox" name="singleInstanceCheckBox">
+         <property name="text">
+          <string>Start only a single instance of KeePassXC</string>
+         </property>
+         <property name="checked">
+          <bool>true</bool>
+         </property>
+        </widget>
+       </item>
        <item>
         <widget class="QCheckBox" name="rememberLastDatabasesCheckBox">
          <property name="text">