Config:systemd: Invoke systemd notify when the compositor is ready

Now the compositor calls systemd notify READY=1 when surfaces can be
created. This allows the use of a systemd notify type start script.

BCS 746-000824

multiscreen-compositor/config.cpp

@@ -3,6 +3,7 @@
 #include <QDebug>
 #include <QRegularExpression>
 #include <QFile>
+#include <systemd/sd-daemon.h>
 
 void Config::setRotation(const QString &str)
 {
@@ -76,3 +77,9 @@ inline bool Config::rotationIsValid(const QString * rotation )
     QStringList validRotations = {"0", "90", "180", "270"};
     return validRotations.contains(*rotation);
 }
+
+void Config::notifyCompositorReady()
+{
+    qDebug() << "Notify systemd that the compositor is ready";
+    sd_notify(false, "READY=1");
+}

multiscreen-compositor/config.h

@@ -12,6 +12,7 @@ public:
 
     void setRotation(const QString &str);
     QString rotation() const;
+    Q_INVOKABLE void notifyCompositorReady();
 private:
     QString m_rotation;
     static const QRegularExpression findRotation;

multiscreen-compositor/multiscreen-compositor.pro

@@ -13,6 +13,9 @@ HEADERS += \
     message-server.h \
     message-serverconnection.h
 
+LIBS += \
+    -lsystemd
+
 OTHER_FILES = \
     qml/main.qml \
 

multiscreen-compositor/qml/main.qml

@@ -110,6 +110,15 @@ WaylandCompositor {
         onIviSurfaceCreated: handleIviSurfaceCreated(iviSurface)
     }
 
+    // =============================================
+    // We need to notify systemd when the compositor
+    // is ready to create surfaces
+    // =============================================
+    onCreatedChanged: {
+        if (created === true) {
+            config.notifyCompositorReady();
+        }
+    }
 
     onSurfaceRequested: {
        console.log("Surface requested", client, id, version);