add bool isUsed() const and remove checkUsage()

datacontainer.cpp

@@ -287,7 +287,7 @@ void DataContainer::disconnectVisualization(QObject *visualization)
     }
 
     d->relayObjects.erase(objIt);
-    checkUsage();
+    d->checkUsage();
 }
 
 void DataContainer::checkForUpdate()
@@ -328,13 +328,18 @@ void DataContainer::setNeedsUpdate(bool update)
     d->cached = update;
 }
 
-void DataContainer::checkUsage()
+bool DataContainer::isUsed() const
 {
-    if (d->relays.count() < 1 &&
-        receivers(SIGNAL(dataUpdated(QString, Plasma::DataEngine::Data))) < 1) {
+    return !d->relays.isEmpty() &&
+           receivers(SIGNAL(dataUpdated(QString, Plasma::DataEngine::Data))) > 0;
+}
+
+void DataContainerPrivate::checkUsage()
+{
+    if (!q->isUsed()) {
         // DO NOT CALL ANYTHING AFTER THIS LINE AS IT MAY GET DELETED!
-        kDebug() << objectName() << "is unused";
-        emit becameUnused(objectName());
+        //kDebug() << q->objectName() << "is unused";
+        emit q->becameUnused(q->objectName());
     }
 }
 

datacontainer.h

@@ -154,6 +154,11 @@ class PLASMA_EXPORT DataContainer : public QObject
          */
         DataEngine* getDataEngine();
 
+        /**
+         * @return true if one or more visualizations is connected to this DataContainer
+         */
+        bool isUsed() const;
+
     public Q_SLOTS:
         /**
          * Disconnects an object from this DataContainer.
@@ -234,17 +239,6 @@ class PLASMA_EXPORT DataContainer : public QObject
          **/
         void setNeedsUpdate(bool update = true);
 
-    protected Q_SLOTS:
-        /**
-         * Check if the DataContainer is still in use.
-         *
-         * If not the signal "becameUnused" will be emitted.
-         *
-         * Warning: The DataContainer may be invalid after calling this function, because a listener
-         * to becameUnused() may have deleted it.
-         **/
-        void checkUsage();
-
     private:
         friend class SignalRelay;
         friend class DataContainerPrivate;

dataengine.cpp

@@ -39,6 +39,7 @@
 #include "service.h"
 #include "scripting/dataenginescript.h"
 
+#include "private/datacontainer_p.h"
 #include "private/dataengineservice_p.h"
 #include "private/remotedataengine_p.h"
 #include "private/service_p.h"
@@ -146,7 +147,7 @@ DataEngine::Data DataEngine::query(const QString &source) const
     }
 
     DataEngine::Data data = s->data();
-    s->checkUsage();
+    s->d->checkUsage();
     return data;
 }
 

private/datacontainer_p.h

@@ -46,6 +46,16 @@ public:
     {
     }
 
+    /**
+     * Check if the DataContainer is still in use.
+     *
+     * If not the signal "becameUnused" will be emitted.
+     *
+     * Warning: The DataContainer may be invalid after calling this function, because a listener
+     * to becameUnused() may have deleted it.
+     **/
+    void checkUsage();
+
     SignalRelay *signalRelay(const DataContainer *dc, QObject *visualization,
                              uint pollingInterval, Plasma::IntervalAlignment align,
                              bool immediateUpdate);