Introduce a compositingChanged signal in KDecorationOptions

Connected from a signal in DecorationPlugins in KWin core replacing
the previous reset method.

decorations.cpp

@@ -46,6 +46,7 @@ DecorationPlugin::DecorationPlugin(QObject *parent)
 #ifdef KWIN_BUILD_DECORATIONS
     loadPlugin(QString());   // load the plugin specified in cfg file
     connect(factory(), &KDecorationFactory::recreateDecorations, this, &DecorationPlugin::recreateDecorations);
+    connect(this, &DecorationPlugin::compositingToggled, options, &KDecorationOptions::compositingChanged);
 #else
     setDisabled(true);
 #endif
@@ -134,14 +135,6 @@ Qt::Corner DecorationPlugin::closeButtonCorner()
     return factory()->closeButtonCorner();
 }
 
-void DecorationPlugin::resetCompositing()
-{
-    if (m_disabled) {
-        return;
-    }
-    factory()->reset(SettingCompositing);
-}
-
 QString DecorationPlugin::supportInformation()
 {
     if (m_disabled) {

decorations.h

@@ -50,8 +50,10 @@ public:
 
     QString supportInformation();
 
+Q_SIGNALS:
+    void compositingToggled();
+
 public Q_SLOTS:
-    void resetCompositing();
     void recreateDecorations();
 protected:
     virtual void error(const QString& error_msg);

libkdecorations/kdecoration.h

@@ -460,6 +460,10 @@ Q_SIGNALS:
      * some decoration specific settings need to be updated.
      */
     void configChanged();
+    /**
+     * @brief Emitted when the compositing state in KWin core changes.
+     */
+    void compositingChanged();
 
 protected:
     /** @internal */

workspace.cpp

@@ -232,7 +232,7 @@ Workspace::Workspace(bool restore)
 
     m_compositor = Compositor::create(this);
     connect(this, SIGNAL(currentDesktopChanged(int,KWin::Client*)), m_compositor, SLOT(addRepaintFull()));
-    connect(m_compositor, SIGNAL(compositingToggled(bool)), decorationPlugin(), SLOT(resetCompositing()));
+    connect(m_compositor, &Compositor::compositingToggled, decorationPlugin(), &DecorationPlugin::compositingToggled);
 
     new DBusInterface(this);