[plasmalnf] Set screenshots on themes, filtering

- while here reorder the config so the effect of *showAll* is clearer

src/modules/plasmalnf/Config.cpp

@@ -58,6 +58,37 @@ Config::setConfigurationMap( const QVariantMap& configurationMap )
         preselect = currentPlasmaTheme();
     }
     m_preselectThemeId = preselect;
+
+    if ( configurationMap.contains( "themes" ) && configurationMap.value( "themes" ).type() == QVariant::List )
+    {
+        QMap< QString, QString > listedThemes;
+        auto themeList = configurationMap.value( "themes" ).toList();
+        // Create the ThemInfo objects for the listed themes; information
+        // about the themes from Plasma (e.g. human-readable name and description)
+        // are filled in by update_names() in PlasmaLnfPage.
+        for ( const auto& i : themeList )
+            if ( i.type() == QVariant::Map )
+            {
+                auto iv = i.toMap();
+                listedThemes.insert( iv.value( "theme" ).toString(), iv.value( "image" ).toString() );
+            }
+            else if ( i.type() == QVariant::String )
+            {
+                listedThemes.insert( i.toString(), QString() );
+            }
+
+        if ( listedThemes.count() == 1 )
+        {
+            cWarning() << "only one theme enabled in plasmalnf";
+        }
+        m_themeModel->setThemeImage( listedThemes );
+
+        bool showAll = CalamaresUtils::getBool( configurationMap, "showAll", false );
+        if ( !listedThemes.isEmpty() && !showAll )
+        {
+            m_themeModel->showOnlyThemes( listedThemes );
+        }
+    }
 }
 
 Calamares::JobList

src/modules/plasmalnf/ThemeInfo.cpp

@@ -90,7 +90,7 @@ ThemesModel::showTheme( const QString& id, bool show )
 }
 
 void
-ThemesModel::showTheme( const QMap< QString, QString >& onlyThese )
+ThemesModel::showOnlyThemes( const QMap< QString, QString >& onlyThese )
 {
     for ( auto& t : m_themes )
     {

src/modules/plasmalnf/ThemeInfo.h

@@ -119,7 +119,7 @@ public:
     void showTheme( const QString& id, bool show = true );
 
     /// @brief Shows the keys in the @p onlyThese map, and hides the rest
-    void showTheme( const QMap< QString, QString >& onlyThese );
+    void showOnlyThemes( const QMap< QString, QString >& onlyThese );
 
 private:
     ThemeInfoList m_themes;

src/modules/plasmalnf/plasmalnf.conf

@@ -24,10 +24,18 @@ lnftool:	"/usr/bin/lookandfeeltool"
 #
 # liveuser:	"live"
 
+# If *showAll* is true, then all installed themes are shown in the
+# UI for selection, even if they are not listed in *themes* (below).
+# This allows selection of all themes even while not all of them are
+# listed in *themes* -- which is useful to show screenshots for those
+# you do have a screenshot for. If *themes* is empty or missing,
+# the value of *showAll* is treated as `true`.
+showAll: false
+
 # You can limit the list of Plasma look-and-feel themes by listing ids
 # here. If this key is not present, all of the installed themes are listed.
 # If the key is present, only installed themes that are **also** included
-# in the list are shown (could be none!). See the *showAll* key, below,
+# in the list are shown (could be none!). See the *showAll* key, above,
 # to change that.
 #
 # Themes may be listed by id, (e.g. fluffy-bunny, below) or as a theme
@@ -58,13 +66,6 @@ themes:
       image: "breeze-dark.png"
     - org.kde.fluffy-bunny.desktop
 
-# If *showAll* is true, then all installed themes are shown in the
-# UI for selection, even if they are not listed in *themes*. This
-# allows selection of all themes even while not all of them are
-# listed in *themes* -- which is useful to show screenshots for those
-# you do have a screenshot for.
-showAll: false
-
 # You can pre-select one of the themes; it is not applied
 # immediately, but its radio-button is switched on to indicate
 # that that is the theme (that is most likely) currently in use.