Implement setBadgeNumber for xcb backend

This use the unity launcher specification which is defined here
https://wiki.ubuntu.com/Unity/LauncherAPI

This spec is used by Plasma and Unity. On other Linux desktop platform
where the unity DBus interface is not detected this is no-op.

Change-Id: I81a9b95fe4886ad597bb4e775641926b161c49a5
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: David Edmundson <davidedmundson@kde.org>

src/gui/kernel/qguiapplication.cpp

@@ -751,7 +751,8 @@ QString QGuiApplication::applicationDisplayName()
     of unread messages or similar.
 
     The badge will be overlaid on the application's icon in the Dock
-    on \macos, the home screen icon on iOS, or the task bar on Windows.
+    on \macos, the home screen icon on iOS, or the task bar on Windows
+    and Linux.
 
     If the number is outside the range supported by the platform, the
     number will be clamped to the supported range. If the number does

src/gui/platform/unix/qgenericunixservices.cpp

@@ -575,6 +575,37 @@ bool QGenericUnixServices::hasCapability(Capability capability) const
     return false;
 }
 
+void QGenericUnixServices::setApplicationBadge(qint64 number)
+{
+#if QT_CONFIG(dbus)
+    if (qGuiApp->desktopFileName().isEmpty()) {
+        qWarning("QGuiApplication::desktopFileName() is empty");
+        return;
+    }
+
+
+    const QString launcherUrl = QStringLiteral("application://") + qGuiApp->desktopFileName() + QStringLiteral(".desktop");
+    const qint64 count = qBound(0, number, 9999);
+    QVariantMap dbusUnityProperties;
+
+    if (count > 0) {
+        dbusUnityProperties[QStringLiteral("count")] = count;
+        dbusUnityProperties[QStringLiteral("count-visible")] = true;
+    } else {
+        dbusUnityProperties[QStringLiteral("count-visible")] = false;
+    }
+
+    auto signal = QDBusMessage::createSignal(QStringLiteral("/com/canonical/unity/launcherentry/")
+        + qGuiApp->applicationName(), QStringLiteral("com.canonical.Unity.LauncherEntry"), QStringLiteral("Update"));
+
+    signal.setArguments({launcherUrl, dbusUnityProperties});
+
+    QDBusConnection::sessionBus().send(signal);
+#else
+    Q_UNUSED(number)
+#endif
+}
+
 QT_END_NAMESPACE
 
 #include "qgenericunixservices.moc"

src/gui/platform/unix/qgenericunixservices_p.h

@@ -35,6 +35,7 @@ public:
     bool openDocument(const QUrl &url) override;
     QPlatformServiceColorPicker *colorPicker(QWindow *parent = nullptr) override;
 
+    void setApplicationBadge(qint64 number);
     virtual QString portalWindowIdentifier(QWindow *window);
 
 private:

src/plugins/platforms/xcb/qxcbintegration.cpp

@@ -585,4 +585,10 @@ QPlatformVulkanInstance *QXcbIntegration::createPlatformVulkanInstance(QVulkanIn
 }
 #endif
 
+void QXcbIntegration::setApplicationBadge(qint64 number)
+{
+    auto unixServices = dynamic_cast<QGenericUnixServices *>(services());
+    unixServices->setApplicationBadge(number);
+}
+
 QT_END_NAMESPACE

src/plugins/platforms/xcb/qxcbintegration.h

@@ -102,6 +102,8 @@ public:
 
     static QXcbIntegration *instance() { return m_instance; }
 
+    void setApplicationBadge(qint64 number) override;
+
 private:
     QXcbConnection *m_connection = nullptr;