provide a way for applets to signal that they'd like their config saved out to disk, please.

svn path=/trunk/KDE/kdebase/workspace/libs/plasma/; revision=755616

applet.h

@@ -581,6 +581,16 @@ class PLASMA_EXPORT Applet : public Widget
          */
         void geometryChanged();
 
+        /**
+         * Emitted when an applet has changed values in its configuration
+         * and wishes for them to be saved at the next save point. As this implies
+         * disk activity, this signal should be used with care.
+         *
+         * @note This does not need to be emitted from saveState by individual
+         * applets.
+         */
+        void configurationChanged();
+
     public Q_SLOTS:
         /**
          * Sets whether or not this applet is immutable or not.

containment.cpp

@@ -473,6 +473,11 @@ Applet* Containment::addApplet(const QString& name, const QVariantList& args, ui
 
     //kDebug() << applet->name() << "sizehint:" << applet->sizeHint() << "geometry:" << applet->geometry();
 
+    Corona *c = corona();
+    if (c) {
+        connect(applet, SIGNAL(configurationChanged()), corona(), SLOT(scheduleConfigSync()));
+    }
+
     emit appletAdded(applet);
     return applet;
 }

corona.cpp

@@ -28,6 +28,7 @@
 #include <QUrl>
 #include <QGraphicsView>
 #include <QStringList>
+#include <QTimer>
 
 #include <KDebug>
 #include <KLocale>
@@ -45,6 +46,10 @@ using namespace Plasma;
 namespace Plasma
 {
 
+// constant controling how long between requesting a configuration sync
+// and one happening should occur. currently 2 minutes.
+const int CONFIG_SYNC_TIMEOUT = 120000;
+
 class Corona::Private
 {
 public:
@@ -64,6 +69,8 @@ public:
 
     void init(Corona* q)
     {
+        configSyncTimer.setSingleShot(true);
+        connect(&configSyncTimer, SIGNAL(timeout()), q, SLOT(syncConfig()));
         QObject::connect(QApplication::desktop(), SIGNAL(resized(int)), q, SLOT(screenResized(int)));
     }
 
@@ -72,6 +79,7 @@ public:
     QString mimetype;
     QString configName;
     KSharedConfigPtr config;
+    QTimer configSyncTimer;
     QList<Containment*> containments;
 };
 
@@ -151,6 +159,18 @@ void Corona::saveApplets() const
     saveApplets(d->configName);
 }
 
+void Corona::scheduleConfigSync()
+{
+    //NOTE: this is a pretty simplistic model: we simply save no more than CONFIG_SYNC_TIMEOUT
+    //      after the first time this is called. not much of a heuristic for save points, but
+    //      it should at least compress these activities a bit and provide a way for applet
+    //      authors to ween themselves from the sync() disease. A more interesting/dynamic
+    //      algorithm for determining when to actually sync() to disk might be better, though.
+    if (!d->configSyncTimer.isActive()) {
+        d->configSyncTimer.start(CONFIG_SYNC_TIMEOUT);
+    }
+}
+
 void Corona::loadApplets(const QString& configName)
 {
     clearApplets();
@@ -292,8 +312,8 @@ void Corona::loadDefaultSetup()
     panel->setLocation(Plasma::LeftEdge);
     */
 
-    // in case something goes bad during runtime, let's at least save this to disk right away
-    config()->sync();
+    // in case something goes bad during runtime, let's at least save this to disk soonish
+    scheduleConfigSync();
 }
 
 Containment* Corona::containmentForScreen(int screen) const
@@ -457,6 +477,11 @@ void Corona::screenResized(int screen)
     emit newScreen(screen);
 }
 
+void Corona::syncConfig()
+{
+    config()->sync();
+}
+
 bool Corona::isImmutable() const
 {
     return d->kioskImmutable || d->immutable;

corona.h

@@ -114,6 +114,12 @@ public Q_SLOTS:
      */
     void saveApplets() const;
 
+    /**
+     * Called when there have been changes made to configuration that should be saved
+     * to disk at the next convenient moment
+     */
+    void scheduleConfigSync();
+
     /**
      * Adds a Containment to the Corona
      *
@@ -177,6 +183,7 @@ protected:
 protected Q_SLOTS:
     void containmentDestroyed(QObject*);
     void screenResized(int);
+    void syncConfig();
 
 private:
     class Private;