Service Type property to exclude KWin Scripts from listing in KCM

This is useful for scripts controlled from other KCMs, like e.g.
DesktopChangeOSD which is controlled by the virtual desktop KCM
and should not be listed in the scripts section.

kcmkwin/kwinscripts/module.cpp

@@ -85,7 +85,7 @@ void Module::importScript()
 
 void Module::updateListViewContents()
 {
-    KService::List offers = KServiceTypeTrader::self()->query("KWin/Script");
+    KService::List offers = KServiceTypeTrader::self()->query("KWin/Script", "not (exist [X-KWin-Exclude-Listing]) or [X-KWin-Exclude-Listing] == false");
     QList<KPluginInfo> scriptinfos = KPluginInfo::fromServices(offers);
     ui->scriptSelector->addPlugins(scriptinfos, KPluginSelector::ReadConfigFile, QString(), QString(), m_kwinConfig);
 }

scripting/kwinscript.desktop

@@ -17,3 +17,6 @@ Type=QString
 
 [PropertyDef::X-Plasma-MainScript]
 Type=QString
+
+[PropertyDef::X-KWin-Exclude-Listing]
+Type=bool

scripts/desktopchangeosd/metadata.desktop

@@ -5,6 +5,7 @@ Icon=preferences-system-windows-script-test
 
 X-Plasma-API=declarativescript
 X-Plasma-MainScript=ui/main.qml
+X-KWin-Exclude-Listing=true
 
 X-KDE-PluginInfo-Author=Martin Gräßlin
 X-KDE-PluginInfo-Email=mgraesslin@kde.org