Allow users to select native notifications on Windows

Setting will fallback to system tray notifications which are
native notifications on Windows.

src/osd/osdbase.cpp

@@ -89,7 +89,11 @@ void OSDBase::ReloadSettings() {
   custom_text2_ = s.value("CustomText2").toString();
   s.endGroup();
 
+#ifdef Q_OS_WIN32
+  if (!SupportsNativeNotifications() && !SupportsTrayPopups() && behaviour_ == Native) {
+#else
   if (!SupportsNativeNotifications() && behaviour_ == Native) {
+#endif
     behaviour_ = Pretty;
   }
 
@@ -302,6 +306,10 @@ void OSDBase::ShowMessage(const QString &summary, const QString &message, const
   else {
     switch (behaviour_) {
       case Native:
+#ifdef Q_OS_WIN32
+      Q_UNUSED(icon)
+      // fallthrough
+#else
         if (image.isNull()) {
           ShowMessageNative(summary, message, icon, QImage());
         }
@@ -309,13 +317,14 @@ void OSDBase::ShowMessage(const QString &summary, const QString &message, const
           ShowMessageNative(summary, message, QString(), image);
         }
         break;
-
+#endif
-#ifndef Q_OS_MACOS
       case TrayPopup:
+#ifdef Q_OS_MACOS
+      // fallthrough
+#else
         if (tray_icon_) tray_icon_->ShowPopup(summary, message, timeout_msec_);
         break;
 #endif
-
       case Disabled:
         if (!force_show_next_) break;
         force_show_next_ = false;
@@ -393,6 +402,8 @@ QString OSDBase::ReplaceMessage(const MessageType type, const QString &message,
         }
       }
       break;
+#elif defined(Q_OS_WIN32)
+    // fallthrough
 #else
       // Other OSes doesn't support native notifications.
       qLog(Debug) << "Native notifications are not supported on this OS.";

src/settings/notificationssettingspage.cpp

@@ -111,10 +111,18 @@ NotificationsSettingsPage::NotificationsSettingsPage(SettingsDialog *dialog, QWi
   QObject::connect(ui_->notifications_exp_chooser2, &QToolButton::triggered, this, &NotificationsSettingsPage::InsertVariableSecondLine);
   QObject::connect(ui_->notifications_disable_duration, &QCheckBox::toggled, ui_->notifications_duration, &NotificationsSettingsPage::setDisabled);
 
+#ifdef Q_OS_WIN32
+  if (!dialog->osd()->SupportsNativeNotifications() && !dialog->osd()->SupportsTrayPopups()) {
+    ui_->notifications_native->setEnabled(false);
+  }
+#else
   if (!dialog->osd()->SupportsNativeNotifications()) {
     ui_->notifications_native->setEnabled(false);
   }
-  if (!dialog->osd()->SupportsTrayPopups()) ui_->notifications_tray->setEnabled(false);
+#endif
+  if (!dialog->osd()->SupportsTrayPopups()) {
+    ui_->notifications_tray->setEnabled(false);
+  }
 
   QObject::connect(ui_->notifications_pretty, &QRadioButton::toggled, this, &NotificationsSettingsPage::UpdatePopupVisible);
 
@@ -150,7 +158,11 @@ void NotificationsSettingsPage::Load() {
   OSDBase::Behaviour osd_behaviour = OSDBase::Behaviour(s.value("Behaviour", OSDBase::Native).toInt());
   switch (osd_behaviour) {
     case OSDBase::Native:
+#ifdef Q_OS_WIN32
+      if (dialog()->osd()->SupportsNativeNotifications() || dialog()->osd()->SupportsTrayPopups()) {
+#else
       if (dialog()->osd()->SupportsNativeNotifications()) {
+#endif
         ui_->notifications_native->setChecked(true);
         break;
       }