Invoke the reinit Compositor signal when the advanced options changed

Therefore we track whether the options got changed and if they did
we emit the reinit signal once the configuration is saved.

kcmkwin/kwincompositing/compositing.cpp

@@ -44,6 +44,7 @@ Compositing::Compositing(QObject *parent)
     , m_glSwapStrategy(0)
     , m_glColorCorrection(false)
     , m_compositingType(0)
+    , m_changed(false)
 {
     reset();
     connect(this, &Compositing::animationSpeedChanged,       this, &Compositing::changed);
@@ -54,6 +55,10 @@ Compositing::Compositing(QObject *parent)
     connect(this, &Compositing::glSwapStrategyChanged,       this, &Compositing::changed);
     connect(this, &Compositing::glColorCorrectionChanged,    this, &Compositing::changed);
     connect(this, &Compositing::compositingTypeChanged,      this, &Compositing::changed);
+
+    connect(this, &Compositing::changed, [this]{
+        m_changed = true;
+    });
 }
 
 void Compositing::reset()
@@ -101,6 +106,7 @@ void Compositing::reset()
         }
     };
     setCompositingType(type());
+    m_changed = false;
 }
 
 void Compositing::defaults()
@@ -113,6 +119,7 @@ void Compositing::defaults()
     setGlSwapStrategy(1);
     setGlColorCorrection(false);
     setCompositingType(CompositingType::OPENGL20_INDEX);
+    m_changed = true;
 }
 
 bool Compositing::OpenGLIsUnsafe() const
@@ -308,6 +315,15 @@ void Compositing::save()
     kwinConfig.writeEntry("GLLegacy", glLegacy);
     kwinConfig.writeEntry("GLCore", glCore);
     kwinConfig.sync();
+
+    if (m_changed) {
+        // Send signal to all kwin instances
+        QDBusMessage message = QDBusMessage::createSignal(QStringLiteral("/Compositor"),
+                                                          QStringLiteral("org.kde.kwin.Compositing"),
+                                                          QStringLiteral("reinit"));
+        QDBusConnection::sessionBus().asyncCall(message);
+        m_changed = false;
+    }
 }
 
 CompositingType::CompositingType(QObject *parent)

kcmkwin/kwincompositing/compositing.h

@@ -89,6 +89,8 @@ private:
     int m_glSwapStrategy;
     bool m_glColorCorrection;
     int m_compositingType;
+
+    bool m_changed;
 };
 
 

kcmkwin/kwincompositing/main.cpp

@@ -23,8 +23,6 @@
 
 #include "model.h"
 #include <QApplication>
-#include <QDBusConnection>
-#include <QDBusMessage>
 #include <QLayout>
 
 #include <kcmodule.h>
@@ -75,10 +73,6 @@ void KWinCompositingKCM::save()
 {
     m_view->save();
     KCModule::save();
-    // Send signal to all kwin instances
-    // TODO: handle reinitCompositing case and send to compositor
-    QDBusMessage message = QDBusMessage::createSignal("/KWin", "org.kde.KWin", "reloadConfig");
-    QDBusConnection::sessionBus().send(message);
 }
 
 void KWinCompositingKCM::load()