Rename QML singleton to Bobink and simplify singleton lifecycle

Replace QML_ELEMENT with QML_NAMED_ELEMENT(Bobink) so QML references
use `Bobink` instead of `BobinkClient`. Remove instance()/create()
factory in favor of inline s_instance set in the constructor. Import
BobinkPlugin statically in demo, link demo to BobinkQtOpcUaplugin,
and make library link dependencies PUBLIC. Add .qtcreator to gitignore.

9 files changed, 168 insertions, 121 deletions

diff --git a/.gitignore b/.gitignore
index ca7b255..625ae33 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,9 @@
-CLAUDE.md
+# IDE / editor
+.qtcreator
 .cache
+
+# Build output
 build
+
+# AI assistant
+CLAUDE.md
diff --git a/demo/CMakeLists.txt b/demo/CMakeLists.txt
index 255a9ee..efdfc72 100644
--- a/demo/CMakeLists.txt
+++ b/demo/CMakeLists.txt
@@ -14,7 +14,7 @@ qt_add_qml_module(
 set_target_properties(BobinkDemo PROPERTIES RUNTIME_OUTPUT_DIRECTORY
                                             "${CMAKE_BINARY_DIR}/bin")
 
-target_link_libraries(BobinkDemo PRIVATE Qt6::Quick BobinkQtOpcUa)
+target_link_libraries(BobinkDemo PRIVATE Qt6::Quick BobinkQtOpcUaplugin)
 
 # Tell the demo where to find the locally-built OpcUa plugin at runtime
 target_compile_definitions(
diff --git a/demo/Main.qml b/demo/Main.qml
index 7b76fee..ef09b7d 100644
--- a/demo/Main.qml
+++ b/demo/Main.qml
@@ -18,15 +18,15 @@ ApplicationWindow {
     property bool showPkiSettings: false
 
     Connections {
-        target: BobinkClient
+        target: Bobink
         function onServersChanged() {
             debugConsole.appendLog("Discovered server list updated");
         }
         function onConnectedChanged() {
-            debugConsole.appendLog("Connected: " + BobinkClient.connected);
-            if (BobinkClient.connected) {
+            debugConsole.appendLog("Connected: " + Bobink.connected);
+            if (Bobink.connected) {
                 root.autoConnectFailed = false;
-                BobinkClient.stopDiscovery();
+                Bobink.stopDiscovery();
                 stack.push("NodePage.qml", {
                     stackRef: stack,
                     pageNumber: 1,
@@ -44,7 +44,7 @@ ApplicationWindow {
             debugConsole.appendLog(message);
         }
         function onDiscoveringChanged() {
-            debugConsole.appendLog("Discovering: " + BobinkClient.discovering);
+            debugConsole.appendLog("Discovering: " + Bobink.discovering);
         }
         function onCertificateTrustRequested(certInfo) {
             certTrustDialog.certInfo = certInfo;
@@ -59,9 +59,11 @@ ApplicationWindow {
         title: "Certificate Trust"
         modal: true
         standardButtons: Dialog.Yes | Dialog.No
-        Label { text: certTrustDialog.certInfo }
-        onAccepted: BobinkClient.acceptCertificate()
-        onRejected: BobinkClient.rejectCertificate()
+        Label {
+            text: certTrustDialog.certInfo
+        }
+        onAccepted: Bobink.acceptCertificate()
+        onRejected: Bobink.rejectCertificate()
     }
 
     ColumnLayout {
@@ -75,8 +77,8 @@ ApplicationWindow {
 
             initialItem: Page {
                 Component.onCompleted: {
-                    BobinkClient.discoveryUrl = discoveryUrlField.text;
-                    BobinkClient.startDiscovery();
+                    Bobink.discoveryUrl = discoveryUrlField.text;
+                    Bobink.startDiscovery();
                 }
 
                 BobinkAuth {
@@ -84,8 +86,8 @@ ApplicationWindow {
                     mode: authModeCombo.currentValue
                     username: usernameField.text
                     password: passwordField.text
-                    certPath: BobinkClient.certFile
-                    keyPath: BobinkClient.keyFile
+                    certPath: Bobink.certFile
+                    keyPath: Bobink.keyFile
                 }
 
                 FileDialog {
@@ -126,22 +128,20 @@ ApplicationWindow {
                             text: "opc.tcp://localhost:4840"
                         }
                         Button {
-                            text: BobinkClient.discovering ? "Stop" : "Discover"
+                            text: Bobink.discovering ? "Stop" : "Discover"
                             onClicked: {
-                                if (BobinkClient.discovering) {
-                                    BobinkClient.stopDiscovery();
+                                if (Bobink.discovering) {
+                                    Bobink.stopDiscovery();
                                 } else {
-                                    BobinkClient.discoveryUrl = discoveryUrlField.text;
-                                    BobinkClient.startDiscovery();
+                                    Bobink.discoveryUrl = discoveryUrlField.text;
+                                    Bobink.startDiscovery();
                                 }
                             }
                         }
                     }
 
                     Label {
-                        text: BobinkClient.discovering
-                              ? "Discovering... (" + BobinkClient.servers.length + " found)"
-                              : BobinkClient.servers.length + " server(s)"
+                        text: Bobink.discovering ? "Discovering... (" + Bobink.servers.length + " found)" : Bobink.servers.length + " server(s)"
                         font.italic: true
                     }
 
@@ -149,7 +149,7 @@ ApplicationWindow {
                         Layout.fillWidth: true
                         Layout.preferredHeight: 100
                         clip: true
-                        model: BobinkClient.servers
+                        model: Bobink.servers
                         delegate: ItemDelegate {
                             required property var modelData
                             width: ListView.view.width
@@ -163,15 +163,18 @@ ApplicationWindow {
                     }
 
                     RowLayout {
-                        Label { text: "PKI"; font.bold: true }
                         Label {
-                            text: BobinkClient.certFile
-                                  ? "  (" + BobinkClient.certFile.split("/").pop() + ")"
-                                  : "  (no certificate found)"
+                            text: "PKI"
+                            font.bold: true
+                        }
+                        Label {
+                            text: Bobink.certFile ? "  (" + Bobink.certFile.split("/").pop() + ")" : "  (no certificate found)"
                             font.italic: true
-                            color: BobinkClient.certFile ? "green" : "gray"
+                            color: Bobink.certFile ? "green" : "gray"
+                        }
+                        Item {
+                            Layout.fillWidth: true
                         }
-                        Item { Layout.fillWidth: true }
                         Button {
                             text: root.showPkiSettings ? "Hide" : "Configure..."
                             flat: true
@@ -184,31 +187,46 @@ ApplicationWindow {
                         Layout.fillWidth: true
                         visible: root.showPkiSettings
 
-                        Label { text: "Certificate:" }
+                        Label {
+                            text: "Certificate:"
+                        }
                         TextField {
                             id: certFileField
                             Layout.fillWidth: true
-                            text: BobinkClient.certFile
+                            text: Bobink.certFile
                             placeholderText: "Client certificate (.der)"
                         }
-                        Button { text: "Browse..."; onClicked: certFileDialog.open() }
+                        Button {
+                            text: "Browse..."
+                            onClicked: certFileDialog.open()
+                        }
 
-                        Label { text: "Private key:" }
+                        Label {
+                            text: "Private key:"
+                        }
                         TextField {
                             id: keyFileField
                             Layout.fillWidth: true
-                            text: BobinkClient.keyFile
+                            text: Bobink.keyFile
                             placeholderText: "Private key (.pem, .crt)"
                         }
-                        Button { text: "Browse..."; onClicked: keyFileDialog.open() }
+                        Button {
+                            text: "Browse..."
+                            onClicked: keyFileDialog.open()
+                        }
 
-                        Label { text: "Trust folder:" }
+                        Label {
+                            text: "Trust folder:"
+                        }
                         TextField {
                             id: trustFolderField
                             Layout.fillWidth: true
-                            text: BobinkClient.pkiDir
+                            text: Bobink.pkiDir
+                        }
+                        Button {
+                            text: "Browse..."
+                            onClicked: trustFolderDialog.open()
                         }
-                        Button { text: "Browse..."; onClicked: trustFolderDialog.open() }
                     }
 
                     Button {
@@ -216,14 +234,17 @@ ApplicationWindow {
                         Layout.fillWidth: true
                         visible: root.showPkiSettings
                         onClicked: {
-                            BobinkClient.pkiDir = trustFolderField.text;
-                            BobinkClient.certFile = certFileField.text;
-                            BobinkClient.keyFile = keyFileField.text;
-                            BobinkClient.applyPki();
+                            Bobink.pkiDir = trustFolderField.text;
+                            Bobink.certFile = certFileField.text;
+                            Bobink.keyFile = keyFileField.text;
+                            Bobink.applyPki();
                         }
                     }
 
-                    Label { text: "Server URL"; font.bold: true }
+                    Label {
+                        text: "Server URL"
+                        font.bold: true
+                    }
 
                     TextField {
                         id: serverUrlField
@@ -231,7 +252,10 @@ ApplicationWindow {
                         placeholderText: "opc.tcp://..."
                     }
 
-                    Label { text: "Authentication"; font.bold: true }
+                    Label {
+                        text: "Authentication"
+                        font.bold: true
+                    }
 
                     ComboBox {
                         id: authModeCombo
@@ -239,9 +263,18 @@ ApplicationWindow {
                         textRole: "text"
                         valueRole: "mode"
                         model: [
-                            { text: "Anonymous", mode: BobinkAuth.Anonymous },
-                            { text: "Username / Password", mode: BobinkAuth.UserPass },
-                            { text: "Certificate", mode: BobinkAuth.Certificate }
+                            {
+                                text: "Anonymous",
+                                mode: BobinkAuth.Anonymous
+                            },
+                            {
+                                text: "Username / Password",
+                                mode: BobinkAuth.UserPass
+                            },
+                            {
+                                text: "Certificate",
+                                mode: BobinkAuth.Certificate
+                            }
                         ]
                     }
 
@@ -250,9 +283,16 @@ ApplicationWindow {
                         visible: authModeCombo.currentValue === BobinkAuth.UserPass
                         Layout.fillWidth: true
 
-                        Label { text: "Username:" }
-                        TextField { id: usernameField; Layout.fillWidth: true }
-                        Label { text: "Password:" }
+                        Label {
+                            text: "Username:"
+                        }
+                        TextField {
+                            id: usernameField
+                            Layout.fillWidth: true
+                        }
+                        Label {
+                            text: "Password:"
+                        }
                         TextField {
                             id: passwordField
                             Layout.fillWidth: true
@@ -265,9 +305,9 @@ ApplicationWindow {
                         Layout.fillWidth: true
                         onClicked: {
                             root.autoConnectFailed = false;
-                            BobinkClient.auth = auth;
-                            BobinkClient.serverUrl = serverUrlField.text;
-                            BobinkClient.connectToServer();
+                            Bobink.auth = auth;
+                            Bobink.serverUrl = serverUrlField.text;
+                            Bobink.connectToServer();
                         }
                     }
 
@@ -282,29 +322,51 @@ ApplicationWindow {
                         Layout.fillWidth: true
                         visible: root.autoConnectFailed
 
-                        Label { text: "Security policy:" }
+                        Label {
+                            text: "Security policy:"
+                        }
                         ComboBox {
                             id: securityPolicyCombo
                             Layout.fillWidth: true
                             textRole: "text"
                             valueRole: "policy"
                             model: [
-                                { text: "Basic256Sha256", policy: BobinkClient.Basic256Sha256 },
-                                { text: "Aes128-Sha256-RsaOaep", policy: BobinkClient.Aes128_Sha256_RsaOaep },
-                                { text: "Aes256-Sha256-RsaPss", policy: BobinkClient.Aes256_Sha256_RsaPss }
+                                {
+                                    text: "Basic256Sha256",
+                                    policy: Bobink.Basic256Sha256
+                                },
+                                {
+                                    text: "Aes128-Sha256-RsaOaep",
+                                    policy: Bobink.Aes128_Sha256_RsaOaep
+                                },
+                                {
+                                    text: "Aes256-Sha256-RsaPss",
+                                    policy: Bobink.Aes256_Sha256_RsaPss
+                                }
                             ]
                         }
 
-                        Label { text: "Security mode:" }
+                        Label {
+                            text: "Security mode:"
+                        }
                         ComboBox {
                             id: securityModeCombo
                             Layout.fillWidth: true
                             textRole: "text"
                             valueRole: "mode"
                             model: [
-                                { text: "Sign & Encrypt", mode: BobinkClient.SignAndEncrypt },
-                                { text: "Sign", mode: BobinkClient.Sign },
-                                { text: "None", mode: BobinkClient.None }
+                                {
+                                    text: "Sign & Encrypt",
+                                    mode: Bobink.SignAndEncrypt
+                                },
+                                {
+                                    text: "Sign",
+                                    mode: Bobink.Sign
+                                },
+                                {
+                                    text: "None",
+                                    mode: Bobink.None
+                                }
                             ]
                         }
                     }
@@ -314,14 +376,15 @@ ApplicationWindow {
                         Layout.fillWidth: true
                         visible: root.autoConnectFailed
                         onClicked: {
-                            BobinkClient.auth = auth;
-                            BobinkClient.serverUrl = serverUrlField.text;
-                            BobinkClient.connectDirect(securityPolicyCombo.currentValue,
-                                                       securityModeCombo.currentValue);
+                            Bobink.auth = auth;
+                            Bobink.serverUrl = serverUrlField.text;
+                            Bobink.connectDirect(securityPolicyCombo.currentValue, securityModeCombo.currentValue);
                         }
                     }
 
-                    Item { Layout.fillHeight: true }
+                    Item {
+                        Layout.fillHeight: true
+                    }
                 }
             }
         }
diff --git a/demo/NodePage.qml b/demo/NodePage.qml
index e4862d8..fd81db5 100644
--- a/demo/NodePage.qml
+++ b/demo/NodePage.qml
@@ -46,7 +46,7 @@ Page {
             Item { Layout.fillWidth: true }
             Button {
                 text: "Disconnect"
-                onClicked: BobinkClient.disconnectFromServer()
+                onClicked: Bobink.disconnectFromServer()
             }
         }
 
diff --git a/demo/main.cpp b/demo/main.cpp
index b52df9e..6d0b9be 100644
--- a/demo/main.cpp
+++ b/demo/main.cpp
@@ -5,18 +5,20 @@
 #include <QGuiApplication>
 #include <QQmlApplicationEngine>
 
+#include <QtQml/QQmlExtensionPlugin>
+Q_IMPORT_QML_PLUGIN(BobinkPlugin)
+
 int main(int argc, char *argv[])
 {
     // Load the locally-built OpcUa backend plugin (open62541).
     QCoreApplication::addLibraryPath(QStringLiteral(QTOPCUA_PLUGIN_PATH));
 
     QGuiApplication app(argc, argv);
-    QQmlApplicationEngine engine;
 
-    QObject::connect(
-        &engine, &QQmlApplicationEngine::objectCreationFailed,
-        &app, []() { QCoreApplication::exit(1); },
-        Qt::QueuedConnection);
+    QQmlApplicationEngine engine;
+    QObject::connect (
+        &engine, &QQmlApplicationEngine::objectCreationFailed, &app,
+        [] () { QCoreApplication::exit (1); }, Qt::QueuedConnection);
 
     engine.loadFromModule("BobinkDemo", "Main");
     return app.exec();
diff --git a/src/BobinkClient.cpp b/src/BobinkClient.cpp
index f8303a3..01f9912 100644
--- a/src/BobinkClient.cpp
+++ b/src/BobinkClient.cpp
@@ -11,8 +11,6 @@
 
 using namespace Qt::Literals::StringLiterals;
 
-BobinkClient *BobinkClient::s_instance = nullptr;
-
 static QString
 defaultPkiDir ()
 {
@@ -36,35 +34,15 @@ BobinkClient::BobinkClient (QObject *parent)
     : QObject (parent), m_provider (new QOpcUaProvider (this)),
       m_pkiDir (defaultPkiDir ())
 {
+  // Singleton pattern: construct only once
+  Q_ASSERT(!s_instance);
   ensurePkiDirs (m_pkiDir);
   setupClient ();
   autoDetectPki ();
   applyPki ();
   connect (&m_discoveryTimer, &QTimer::timeout, this,
            &BobinkClient::doDiscovery);
-}
-
-BobinkClient::~BobinkClient ()
-{
-  if (s_instance == this)
-    s_instance = nullptr;
-}
-
-BobinkClient *
-BobinkClient::instance ()
-{
-  return s_instance;
-}
-
-BobinkClient *
-BobinkClient::create (QQmlEngine *, QJSEngine *)
-{
-  if (!s_instance)
-    {
-      s_instance = new BobinkClient;
-      QJSEngine::setObjectOwnership (s_instance, QJSEngine::CppOwnership);
-    }
-  return s_instance;
+  s_instance = this;
 }
 
 void
diff --git a/src/BobinkClient.h b/src/BobinkClient.h
index 5b7b284..3f36e75 100644
--- a/src/BobinkClient.h
+++ b/src/BobinkClient.h
@@ -25,8 +25,8 @@ class BobinkAuth;
 class BobinkClient : public QObject
 {
   Q_OBJECT
-  QML_ELEMENT
   QML_SINGLETON
+  QML_NAMED_ELEMENT (Bobink)
 
   Q_PROPERTY (bool connected READ connected NOTIFY connectedChanged)
   Q_PROPERTY (QString serverUrl READ serverUrl WRITE setServerUrl NOTIFY
@@ -45,16 +45,18 @@ class BobinkClient : public QObject
       QString keyFile READ keyFile WRITE setKeyFile NOTIFY keyFileChanged)
 
 public:
-  explicit BobinkClient (QObject *parent = nullptr);
-  ~BobinkClient () override;
+  BobinkClient (QObject *parent = nullptr);
+  // ~BobinkClient () override;
 
-  static BobinkClient *instance ();
+  static inline BobinkClient *s_instance = nullptr;
+
+  // static BobinkClient *instance ();
 
   /**
    * @brief  QML singleton factory.
    * @note   CppOwnership — lives for the process lifetime.
    */
-  static BobinkClient *create (QQmlEngine *qmlEngine, QJSEngine *jsEngine);
+  // static BobinkClient *create (QQmlEngine *qmlEngine, QJSEngine *jsEngine);
 
   bool connected () const;
 
@@ -155,7 +157,6 @@ private slots:
 private:
   void setupClient ();
 
-  static BobinkClient *s_instance;
   QOpcUaProvider *m_provider = nullptr;
   QOpcUaClient *m_client = nullptr;
   BobinkAuth *m_auth = nullptr;
diff --git a/src/BobinkNode.cpp b/src/BobinkNode.cpp
index a39c195..fed87bc 100644
--- a/src/BobinkNode.cpp
+++ b/src/BobinkNode.cpp
@@ -104,7 +104,7 @@ BobinkNode::componentComplete ()
   QQuickItem::componentComplete ();
   m_componentComplete = true;
 
-  auto *client = BobinkClient::instance ();
+  auto *client = BobinkClient::s_instance;
   if (client)
     connect (client, &BobinkClient::connectedChanged, this,
              &BobinkNode::handleClientConnectedChanged);
@@ -137,7 +137,7 @@ BobinkNode::startMonitoring ()
   if (m_opcuaNode || m_nodeId.isEmpty ())
     return;
 
-  auto *client = BobinkClient::instance ();
+  auto *client = BobinkClient::s_instance;
   if (!client || !client->connected ())
     return;
 
@@ -245,11 +245,10 @@ BobinkNode::handleAttributeWritten (QOpcUa::NodeAttribute attr,
 void
 BobinkNode::handleClientConnectedChanged ()
 {
-  auto *client = BobinkClient::instance ();
-  if (!client)
+  if (!BobinkClient::s_instance)
     return;
 
-  if (client->connected ())
+  if (BobinkClient::s_instance->connected ())
     {
       if (m_componentComplete && isVisible ())
         startMonitoring ();
@@ -263,8 +262,7 @@ BobinkNode::handleClientConnectedChanged ()
 void
 BobinkNode::handleAttributeReadFinished (QOpcUa::NodeAttributes attrs)
 {
-  auto *client = BobinkClient::instance ();
-  if (!client || !m_opcuaNode)
+  if (!BobinkClient::s_instance || !m_opcuaNode)
     return;
 
   for (int bit = 0; bit < 27; ++bit)
@@ -276,12 +274,12 @@ BobinkNode::handleAttributeReadFinished (QOpcUa::NodeAttributes attrs)
       auto sc = m_opcuaNode->attributeError (attr);
       QLatin1StringView name = nameFromAttribute (attr);
       if (sc == QOpcUa::UaStatusCode::Good)
-        emit client->statusMessage (
+        emit BobinkClient::s_instance->statusMessage (
             QStringLiteral ("Read %1.%2 = %3")
                 .arg (m_nodeId, name,
                       m_opcuaNode->attribute (attr).toString ()));
       else
-        emit client->statusMessage (
+        emit BobinkClient::s_instance->statusMessage (
             QStringLiteral ("Read %1.%2 failed: 0x%3")
                 .arg (m_nodeId, name)
                 .arg (static_cast<quint32> (sc), 8, 16, QLatin1Char ('0')));
@@ -292,15 +290,14 @@ void
 BobinkNode::handleEnableMonitoringFinished (QOpcUa::NodeAttribute,
                                             QOpcUa::UaStatusCode statusCode)
 {
-  auto *client = BobinkClient::instance ();
-  if (!client)
+  if (!BobinkClient::s_instance)
     return;
 
   if (statusCode == QOpcUa::Good)
-    emit client->statusMessage (
+    emit BobinkClient::s_instance->statusMessage (
         QStringLiteral ("Monitoring started: %1").arg (m_nodeId));
   else
-    emit client->statusMessage (
+    emit BobinkClient::s_instance->statusMessage (
         QStringLiteral ("Monitoring failed for %1: 0x%2")
             .arg (m_nodeId)
             .arg (static_cast<quint32> (statusCode), 8, 16,
@@ -311,15 +308,14 @@ void
 BobinkNode::handleDisableMonitoringFinished (QOpcUa::NodeAttribute,
                                              QOpcUa::UaStatusCode statusCode)
 {
-  auto *client = BobinkClient::instance ();
-  if (!client)
+  if (!BobinkClient::s_instance)
     return;
 
   if (statusCode == QOpcUa::Good)
-    emit client->statusMessage (
+    emit BobinkClient::s_instance->statusMessage (
         QStringLiteral ("Monitoring stopped: %1").arg (m_nodeId));
   else
-    emit client->statusMessage (
+    emit BobinkClient::s_instance->statusMessage (
         QStringLiteral ("Stop monitoring failed for %1: 0x%2")
             .arg (m_nodeId)
             .arg (static_cast<quint32> (statusCode), 8, 16,
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 5898132..1292194 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1,3 +1,4 @@
+qt_add_library(BobinkQtOpcUa STATIC)
 # BobinkQtOpcUa — QML module wrapping QtOpcUa for declarative use.
 qt_add_qml_module(
   BobinkQtOpcUa
@@ -15,4 +16,4 @@ qt_add_qml_module(
   OUTPUT_DIRECTORY
   "${CMAKE_BINARY_DIR}/qml/Bobink")
 
-target_link_libraries(BobinkQtOpcUa PRIVATE Qt6::Core Qt6::Quick Qt6::OpcUa)
+target_link_libraries(BobinkQtOpcUa PUBLIC Qt6::Core Qt6::Quick Qt6::OpcUa)