[plasmalnf] New setting to show all installed LnF themes

- This enables working in three modes:
   - No themes listed; all are shown without screenshots,
   - Themes listed, showAll false; only those are shown,
   - Themes listed, showAll true; the installed-but-not-listed
     themes are shown after the listed ones, and have limited info.

src/modules/plasmalnf/PlasmaLnfPage.cpp

@@ -57,6 +57,7 @@ static ThemeInfoList plasma_themes()
 PlasmaLnfPage::PlasmaLnfPage( QWidget* parent )
     : QWidget( parent )
     , ui( new Ui::PlasmaLnfPage )
+    , m_showAll( false )
     , m_buttonGroup( nullptr )
 {
     ui->setupUi( this );
@@ -85,6 +86,14 @@ PlasmaLnfPage::setEnabledThemes(const ThemeInfoList& themes)
 {
     m_enabledThemes = themes;
 
+    if ( m_showAll )
+    {
+        auto plasmaThemes = plasma_themes();
+        for ( auto& installed_theme : plasmaThemes )
+            if ( !m_enabledThemes.findById( installed_theme.id ) )
+                m_enabledThemes.append( installed_theme );
+    }
+
     updateThemeNames();
     winnowThemes();
     fillUi();
@@ -104,6 +113,12 @@ PlasmaLnfPage::setPreselect( const QString& id )
         fillUi();
 }
 
+void
+PlasmaLnfPage::setShowAll(bool b)
+{
+    m_showAll = b;
+}
+
 
 void PlasmaLnfPage::updateThemeNames()
 {

src/modules/plasmalnf/PlasmaLnfPage.h

@@ -52,6 +52,8 @@ public:
     void setEnabledThemesAll();
     /** @brief set which theme is to be preselected. */
     void setPreselect( const QString& id );
+    /** @brief set whether to show all themes, not just the listed ones. */
+    void setShowAll( bool b );
 
 signals:
     void plasmaThemeSelected( const QString& id );
@@ -67,6 +69,7 @@ private:
     Ui::PlasmaLnfPage* ui;
     QString m_lnfPath;
     QString m_preselect;
+    bool m_showAll;  // If true, don't winnow according to enabledThemes
     ThemeInfoList m_enabledThemes;
 
     QButtonGroup *m_buttonGroup;

src/modules/plasmalnf/PlasmaLnfViewStep.cpp

@@ -162,6 +162,11 @@ PlasmaLnfViewStep::setConfigurationMap( const QVariantMap& configurationMap )
     if ( !preselect.isEmpty() )
         m_widget->setPreselect( preselect );
 
+    bool showAll( false );
+    if ( configurationMap.contains( "showAll" ) && configurationMap.value( "showAll" ).type() == QVariant::Bool )
+        showAll = configurationMap.value( "showAll" ).toBool();
+    m_widget->setShowAll( showAll );
+
     if ( configurationMap.contains( "themes" ) &&
         configurationMap.value( "themes" ).type() == QVariant::List )
     {

src/modules/plasmalnf/plasmalnf.conf

@@ -13,8 +13,9 @@ lnftool:	"/usr/bin/lookandfeeltool"
 
 # 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!).
+# 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,
+# to change that.
 #
 # Themes may be listed by id, (e.g. fluffy-bunny, below) or as a theme
 # and an image (e.g. breeze) which will be used to show a screenshot.
@@ -28,6 +29,13 @@ 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.