Add activeOutputName to DBus interface

Provide the name of the active output via the DBus interface, so it can
be used by other components, like KRunner (see bug 427069).

CCBUG: 427069

src/dbusinterface.cpp

@@ -15,6 +15,7 @@
 
 // kwin
 #include "abstract_client.h"
+#include "abstract_output.h"
 #include "atoms.h"
 #include "composite.h"
 #include "debug_console.h"
@@ -129,6 +130,11 @@ WRAP(QString, supportInformation)
 
 #undef WRAP
 
+QString DBusInterface::activeOutputName()
+{
+    return Workspace::self()->activeOutput()->name();
+}
+
 bool DBusInterface::startActivity(const QString &in0)
 {
 #if KWIN_BUILD_ACTIVITIES

src/dbusinterface.h

@@ -56,6 +56,7 @@ public Q_SLOTS: // METHODS
     bool startActivity(const QString &in0);
     bool stopActivity(const QString &in0);
     QString supportInformation();
+    QString activeOutputName();
     Q_NOREPLY void unclutterDesktop();
     Q_NOREPLY void showDebugConsole();
 

src/org.kde.KWin.xml

@@ -35,6 +35,9 @@
     <method name="supportInformation">
         <arg type="s" direction="out"/>
     </method>
+    <method name="activeOutputName">
+        <arg type="s" direction="out"/>
+    </method>
     <method name="showDebugConsole"/>
     <method name="replace"/>
     <method name="queryWindowInfo">