* count the number of objects connected to each datasource

* data sources now signal when the are unused
* listen to the unused signal for sources created on demand via dataSourceRequested

svn path=/trunk/KDE/kdebase/workspace/lib/plasma/; revision=673389

dataengine.cpp

@@ -64,9 +64,9 @@ class DataEngine::Private
                 return 0;
             }
 
-            kDebug() << "DataEngine " << engine->objectName()
+/*            kDebug() << "DataEngine " << engine->objectName()
                      << ": could not find DataSource " << sourceName
-                     << ", creating" << endl;
+                     << ", creating" << endl;*/
             DataSource* s = new DataSource(engine);
             s->setObjectName(sourceName);
             sources.insert(sourceName, s);
@@ -137,10 +137,19 @@ void DataEngine::connectSource(const QString& source, QObject* visualization) co
     DataSource* s = d->source(source, false);
 
     if (!s) {
-        kDebug() << "requesting source " << source << endl;
-        d->dataSourceRequested(source);
-        s = d->source(source);
-        kDebug() << "and no we have " << s << endl;
+        // we didn't find a data source, so give the engine an opportunity to make one
+        if (d->dataSourceRequested(source)) {
+            s = d->source(source);
+            if (s) {
+                // now we have a source; since it was created on demand, assume
+                // it should be removed when not used
+                connect(s, SIGNAL(unused(QString)), this, SLOT(removeDataSource(QString)));
+            }
+        }
+    }
+
+    if (!s) {
+        return;
     }
 
     connect(s, SIGNAL(updated(QString,Plasma::DataEngine::Data)),
@@ -150,6 +159,18 @@ void DataEngine::connectSource(const QString& source, QObject* visualization) co
                               Q_ARG(Plasma::DataEngine::Data, s->data()));
 }
 
+void DataEngine::disconnectSource(const QString& source, QObject* visualization) const
+{
+    DataSource* s = d->source(source, false);
+
+    if (!s) {
+        return;
+    }
+
+    disconnect(s, SIGNAL(updated(QString,Plasma::DataEngine::Data)),
+               visualization, SLOT(updated(QString,Plasma::DataEngine::Data)));
+}
+
 void DataEngine::connectAllSources(QObject* visualization) const
 {
     foreach (const DataSource* s, d->sources) {
@@ -238,6 +259,7 @@ Plasma::DataSource* DataEngine::createDataSource(const QString& source, const QS
 
 void DataEngine::removeDataSource(const QString& source)
 {
+    //kDebug() << "removing source " << source << endl;
     SourceDict::iterator it = d->sources.find(source);
     if (it != d->sources.end()) {
         emit dataSourceRemoved(it.key());

dataengine.h

@@ -85,6 +85,14 @@ class PLASMA_EXPORT DataEngine : public QObject
          **/
         void connectSource(const QString& source, QObject* visualization) const;
 
+        /**
+         * Disconnects a source to an object that was receiving data updates.
+         *
+         * @param source the name of the data source
+         * @param visualization the object to connect the data source to
+         **/
+        void disconnectSource(const QString& source, QObject* visualization) const;
+
         /**
          * Connects all sources to an object for data updates. The object must
          * have a slot with the following signature:
@@ -215,12 +223,6 @@ class PLASMA_EXPORT DataEngine : public QObject
         void createDataSource(const QString& source,
                               const QString& domain = QString());*/
 
-        /**
-         * Removes a data source.
-         * @param source the name of the data source to remove
-         **/
-        void removeDataSource(const QString& source);
-
         /**
          * Removes all data sources
          **/
@@ -247,6 +249,12 @@ class PLASMA_EXPORT DataEngine : public QObject
          */
         void checkForUpdates();
 
+        /**
+         * Removes a data source.
+         * @param source the name of the data source to remove
+         **/
+        void removeDataSource(const QString& source);
+
     private:
         class Private;
         Private* const d;

datasource.cpp

@@ -18,6 +18,7 @@
 
 #include "datasource.h"
 
+#include <QAtomic>
 #include <QVariant>
 
 #include <KDebug>
@@ -25,7 +26,6 @@
 namespace Plasma
 {
 
-
 class DataSource::Private
 {
     public:
@@ -34,7 +34,8 @@ class DataSource::Private
         {}
 
         DataEngine::Data data;
-        bool dirty;
+        QAtomic connectCount;
+        bool dirty : 1;
 };
 
 DataSource::DataSource(QObject* parent)
@@ -67,6 +68,27 @@ void DataSource::checkForUpdate()
     }
 }
 
+void DataSource::connectNotify(const char *signal)
+{
+    if (QLatin1String(signal) == QMetaObject::normalizedSignature(SIGNAL(updated(QString, Plasma::DataEngine::Data))).constData()) {
+        d->connectCount.ref();
+    }
+}
+
+void DataSource::disconnectNotify(const char *signal)
+{
+    if (QLatin1String(signal) == QMetaObject::normalizedSignature(SIGNAL(updated(QString, Plasma::DataEngine::Data))).constData()) {
+        if (d->connectCount > 0) {
+            d->connectCount.deref();
+        }
+
+        if (d->connectCount < 1) {
+            // DO NOT CALL ANYTHING AFTER THIS LINE AS IT MAY GET DELETED!
+            emit unused(objectName());
+        }
+    }
+}
+
 } // Plasma namespace
 
 #include "datasource.moc"

datasource.h

@@ -80,6 +80,15 @@ class PLASMA_EXPORT DataSource : public QObject
          **/
         void updated(const QString& source, const Plasma::DataEngine::Data& data);
 
+        /**
+         * Emitted when this source becomes unused
+         **/
+        void unused(const QString& source);
+
+    protected:
+        void connectNotify(const char *signal);
+        void disconnectNotify(const char *signal);
+
     private:
         class Private;
         Private* const d;