[plasmalnf] Apply workaround for lookandfeeltool

The lookandfeeltool does not (always?) write the LookAndFeelPackage
key that the KCM does -- and which this module reads on startup
to find the default LnF. This seems to be a regression in recent
lookandfeeltool versions (or in the KCM code that backs it).

Workaround supplied by jghodd.

Fixes #1573

src/modules/plasmalnf/PlasmaLnfJob.cpp

@@ -14,6 +14,11 @@
 #include "utils/CalamaresUtilsSystem.h"
 #include "utils/Logger.h"
 
+#ifdef WITH_KCONFIG
+#include <KConfigGroup>
+#include <KSharedConfig>
+#endif
+
 PlasmaLnfJob::PlasmaLnfJob( const QString& lnfPath, const QString& id )
     : m_lnfPath( lnfPath )
     , m_id( id )
@@ -53,5 +58,15 @@ PlasmaLnfJob::exec()
                                             tr( "Could not select KDE Plasma Look-and-Feel package" ) );
     }
 
+#ifdef WITH_KCONFIG
+    // This is a workaround for lookandfeeltool **not** writing
+    // the LookAndFeelPackage key in kdeglobals; this happens
+    // with the lnftool and Plasma 5.20 (possibly other combinations
+    // as well).
+    QString targetConfig = system->targetPath( "/home/" + gs->value( "username" ).toString() + "/.config/kdeglobals" );
+    KConfigGroup cg( KSharedConfig::openConfig( targetConfig ), "KDE" );
+    cg.writeEntry( "LookAndFeelPackage", m_id );
+#endif
+
     return Calamares::JobResult::ok();
 }