Only allow a single instance of program to be run at a time

.gitmodules

@@ -5,3 +5,6 @@
 [submodule "gpt4all-chat/usearch"]
 	path = gpt4all-chat/deps/usearch
 	url = https://github.com/nomic-ai/usearch.git
+[submodule "gpt4all-chat/deps/SingleApplication"]
+	path = gpt4all-chat/deps/SingleApplication
+	url = https://github.com/nomic-ai/SingleApplication.git

gpt4all-chat/CHANGELOG.md

@@ -12,6 +12,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ### Changed
 - Smaller default window size, dynamic minimum size, and scaling tweaks ([#2904](https://github.com/nomic-ai/gpt4all/pull/2904))
+- Only allow a single instance of program to be run at a time ([#2923](https://github.com/nomic-ai/gpt4all/pull/2923]))
 
 ### Fixed
 - Bring back "Auto" option for Embeddings Device as "Application default," which went missing in v3.1.0 ([#2873](https://github.com/nomic-ai/gpt4all/pull/2873))

gpt4all-chat/CMakeLists.txt

@@ -105,6 +105,8 @@ if (APPLE)
     list(APPEND CHAT_EXE_RESOURCES "${LOCAL_EMBEDDING_MODEL_PATH}")
 endif()
 
+set(QAPPLICATION_CLASS QGuiApplication)
+add_subdirectory(deps/SingleApplication)
 add_subdirectory(src)
 
 target_sources(chat PRIVATE ${APP_ICON_RESOURCE} ${CHAT_EXE_RESOURCES})
@@ -238,7 +240,7 @@ else()
     PRIVATE Qt6::Quick Qt6::Svg Qt6::HttpServer Qt6::Sql Qt6::Pdf)
 endif()
 target_link_libraries(chat
-    PRIVATE llmodel)
+    PRIVATE llmodel SingleApplication)
 
 
 # -- install --

gpt4all-chat/src/main.cpp

@@ -9,22 +9,44 @@
 #include "network.h"
 
 #include <gpt4all-backend/llmodel.h>
+#include <singleapplication.h>
 
 #include <QCoreApplication>
-#include <QGuiApplication>
 #include <QObject>
 #include <QQmlApplicationEngine>
-#include <QQmlEngine>
+#include <QQuickWindow>
 #include <QSettings>
 #include <QString>
-#include <QTranslator>
 #include <QUrl>
 #include <Qt>
 
 #ifdef Q_OS_LINUX
 #   include <QIcon>
 #endif
 
+#ifdef Q_OS_WINDOWS
+#   include <windows.h>
+#endif
+
+using namespace Qt::Literals::StringLiterals;
+
+
+static void raiseWindow(QWindow *window)
+{
+#ifdef Q_OS_WINDOWS
+    HWND hwnd = HWND(window->winId());
+
+    // check if window is minimized to Windows task bar
+    if (IsIconic(hwnd))
+        ShowWindow(hwnd, SW_RESTORE);
+
+    SetForegroundWindow(hwnd);
+#else
+    window->show();
+    window->raise();
+    window->requestActivate();
+#endif
+}
 
 int main(int argc, char *argv[])
 {
@@ -36,7 +58,15 @@ int main(int argc, char *argv[])
 
     Logger::globalInstance();
 
-    QGuiApplication app(argc, argv);
+    SingleApplication app(argc, argv, true /*allowSecondary*/);
+    if (app.isSecondary()) {
+#ifdef Q_OS_WINDOWS
+        AllowSetForegroundWindow(DWORD(app.primaryPid()));
+#endif
+        app.sendMessage("RAISE_WINDOW");
+        return 0;
+    }
+
 #ifdef Q_OS_LINUX
     app.setWindowIcon(QIcon(":/gpt4all/icons/gpt4all.svg"));
 #endif
@@ -77,7 +107,7 @@ int main(int argc, char *argv[])
     qmlRegisterSingletonInstance("localdocs", 1, 0, "LocalDocs", LocalDocs::globalInstance());
     qmlRegisterUncreatableMetaObject(MySettingsEnums::staticMetaObject, "mysettingsenums", 1, 0, "MySettingsEnums", "Error: only enums");
 
-    const QUrl url(u"qrc:/gpt4all/main.qml"_qs);
+    const QUrl url(u"qrc:/gpt4all/main.qml"_s);
 
     QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
         &app, [url](QObject *obj, const QUrl &objUrl) {
@@ -86,6 +116,13 @@ int main(int argc, char *argv[])
         }, Qt::QueuedConnection);
     engine.load(url);
 
+    QObject *rootObject = engine.rootObjects().first();
+    QQuickWindow *windowObject = qobject_cast<QQuickWindow *>(rootObject);
+    Q_ASSERT(windowObject);
+    if (windowObject)
+        QObject::connect(&app, &SingleApplication::receivedMessage,
+                         windowObject, [windowObject] () { raiseWindow(windowObject); } );
+
 #if 0
     QDirIterator it("qrc:", QDirIterator::Subdirectories);
     while (it.hasNext()) {