Refresh plasmashell when the ShellPackage changes from the LnF

At the moment issues a --replace that will restart the package, will
need to look into why it crashes when tearing up the former shell
package.

kcms/lookandfeel/kcm.cpp

@@ -410,6 +410,12 @@ void KCMLookandFeel::save()
             QDBusConnection::sessionBus().send(message);
         }
 
+        if (m_plasmashellChanged) {
+            QDBusMessage message =
+                QDBusMessage::createSignal(QStringLiteral("/PlasmaShell"), QStringLiteral("org.kde.PlasmaShell"), QStringLiteral("refreshCurrentShell"));
+            QDBusConnection::sessionBus().send(message);
+        }
+
         // autostart
         if (m_resetDefaultLayout) {
             // remove all the old package to autostart
@@ -759,6 +765,7 @@ void KCMLookandFeel::setWindowPlacement(const QString &value)
 void KCMLookandFeel::setShellPackage(const QString &value)
 {
     writeNewDefaults(QStringLiteral("plasmashellrc"), QStringLiteral("Shell"), QStringLiteral("ShellPackage"), value);
+    m_plasmashellChanged = true;
 }
 
 void KCMLookandFeel::setWindowDecoration(const QString &library, const QString &theme)

kcms/lookandfeel/kcm.h

@@ -138,4 +138,6 @@ private:
     bool m_applyShellPackage : 1 = true;
     bool m_resetDefaultLayout : 1;
     bool m_applyWindowDecoration : 1;
+
+    bool m_plasmashellChanged = false;
 };

shell/dbus/org.kde.PlasmaShell.xml

@@ -23,5 +23,6 @@
     </method>
     <method name="activateLauncherMenu">
     </method>
+    <method name="refreshCurrentShell" />
   </interface>
 </node>

shell/main.cpp

@@ -98,10 +98,6 @@ int main(int argc, char *argv[])
 
     app.setQuitOnLastWindowClosed(false);
 
-    KSharedConfig::Ptr startupConf = KSharedConfig::openConfig(QStringLiteral("plasmashellrc"));
-    KConfigGroup startupConfGroup(startupConf, "Shell");
-    const QString defaultShell = startupConfGroup.readEntry("ShellPackage", qEnvironmentVariable("PLASMA_DEFAULT_SHELL", "org.kde.plasma.desktop"));
-
     bool replace = false;
 
     ShellCorona *corona;
@@ -116,7 +112,7 @@ int main(int argc, char *argv[])
         QCommandLineOption shellPluginOption(QStringList() << QStringLiteral("p") << QStringLiteral("shell-plugin"),
                                              i18n("Force loading the given shell plugin"),
                                              QStringLiteral("plugin"),
-                                             defaultShell);
+                                             ShellCorona::defaultShell());
 
         QCommandLineOption standaloneOption(QStringList() << QStringLiteral("a") << QStringLiteral("standalone"),
                                             i18n("Load plasmashell as a standalone application, needs the shell-plugin option to be specified"));

shell/shellcorona.cpp

@@ -2127,6 +2127,20 @@ void ShellCorona::activateTaskManagerEntry(int index)
     }
 }
 
+QString ShellCorona::defaultShell()
+{
+    KSharedConfig::Ptr startupConf = KSharedConfig::openConfig(QStringLiteral("plasmashellrc"));
+    KConfigGroup startupConfGroup(startupConf, "Shell");
+    return startupConfGroup.readEntry("ShellPackage", qEnvironmentVariable("PLASMA_DEFAULT_SHELL", "org.kde.plasma.desktop"));
+}
+
+void ShellCorona::refreshCurrentShell()
+{
+    KSharedConfig::openConfig(QStringLiteral("plasmashellrc"))->reparseConfiguration();
+    //  FIXME:   setShell(defaultShell());
+    QProcess::startDetached("plasmashell", {"--replace"});
+}
+
 // Desktop corona handler
 
 #include "moc_shellcorona.cpp"

shell/shellcorona.h

@@ -106,6 +106,8 @@ public:
 
     QString defaultContainmentPlugin() const;
 
+    static QString defaultShell();
+
 Q_SIGNALS:
     void glInitializationFailed();
 
@@ -158,6 +160,8 @@ public Q_SLOTS:
         return m_panelViews.count();
     }
 
+    void refreshCurrentShell();
+
 protected Q_SLOTS:
     /**
      * Loads the layout and performs the needed checks