GUI: Initialise DBus notifications in another thread

QDBusInterface's constructor can hang if org.freedesktop.Notifications is missing, so avoid delaying startup waiting for a timeout

Author: luke-jr

src/qt/notificator.cpp

@@ -31,6 +31,18 @@
 #ifdef USE_DBUS
 // https://wiki.ubuntu.com/NotificationDevelopmentGuidelines recommends at least 128
 const int FREEDESKTOP_NOTIFICATION_ICON_SIZE = 128;
+
+void DBusInitThread::run() {
+    auto interface = new QDBusInterface("org.freedesktop.Notifications", "/org/freedesktop/Notifications", "org.freedesktop.Notifications");
+    if (!interface->isValid()) {
+        delete interface;
+        return;
+    }
+    interface->moveToThread(m_notificator.thread());
+    m_notificator.interface = interface;
+    m_notificator.mode = Notificator::Freedesktop;
+}
+
 #endif
 
 Notificator::Notificator(const QString &programName, QSystemTrayIcon *trayicon, QWidget *parent) :
@@ -48,12 +60,8 @@ Notificator::Notificator(const QString &programName, QSystemTrayIcon *trayicon,
         mode = QSystemTray;
     }
 #ifdef USE_DBUS
-    interface = new QDBusInterface("org.freedesktop.Notifications",
-        "/org/freedesktop/Notifications", "org.freedesktop.Notifications");
-    if(interface->isValid())
-    {
-        mode = Freedesktop;
-    }
+    m_dbus_init_thread = new DBusInitThread(*this);
+    m_dbus_init_thread->start();
 #endif
 #ifdef Q_OS_MAC
     // check if users OS has support for NSUserNotification
@@ -82,6 +90,8 @@ Notificator::Notificator(const QString &programName, QSystemTrayIcon *trayicon,
 Notificator::~Notificator()
 {
 #ifdef USE_DBUS
+    m_dbus_init_thread->wait();
+    delete m_dbus_init_thread;
     delete interface;
 #endif
 }
@@ -296,8 +306,7 @@ void Notificator::notifyMacUserNotificationCenter(Class cls, const QString &titl
 
 void Notificator::notify(Class cls, const QString &title, const QString &text, const QIcon &icon, int millisTimeout)
 {
-    switch(mode)
-    {
+    switch (Mode(mode)) {
 #ifdef USE_DBUS
     case Freedesktop:
         notifyDBus(cls, title, text, icon, millisTimeout);

src/qt/notificator.h

@@ -11,6 +11,9 @@
 
 #include <QIcon>
 #include <QObject>
+#include <QThread>
+
+#include <atomic>
 
 QT_BEGIN_NAMESPACE
 class QSystemTrayIcon;
@@ -20,6 +23,23 @@ class QDBusInterface;
 #endif
 QT_END_NAMESPACE
 
+class Notificator;
+
+#ifdef USE_DBUS
+class DBusInitThread : public QThread
+{
+    Q_OBJECT
+
+    Notificator& m_notificator;
+
+public:
+    DBusInitThread(Notificator& notificator) : m_notificator(notificator) {};
+
+protected:
+    void run() override;
+};
+#endif
+
 /** Cross-platform desktop notification client. */
 class Notificator: public QObject
 {
@@ -63,11 +83,15 @@ public slots:
         UserNotificationCenter      /**< Use the 10.8+ User Notification Center (Mac only) */
     };
     QString programName;
-    Mode mode;
+    std::atomic<Mode> mode;
     QSystemTrayIcon *trayIcon;
 #ifdef USE_DBUS
+    QThread *m_dbus_init_thread{nullptr};
+protected:
     QDBusInterface *interface;
+    friend class DBusInitThread;
 
+private:
     void notifyDBus(Class cls, const QString &title, const QString &text, const QIcon &icon, int millisTimeout);
 #endif
     void notifySystray(Class cls, const QString &title, const QString &text, const QIcon &icon, int millisTimeout);