[libcalamares] Support looking up translation by 2-letter country

- Looks for an available translation by 2-letter country code
   and returns the row for it.

src/libcalamares/locale/Label.h

@@ -92,6 +92,18 @@ public:
         return m_locale.name();
     }
 
+    /// @brief Convenience accessor to the language part of the locale
+    QLocale::Language language() const
+    {
+        return m_locale.language();
+    }
+
+    /// @brief Convenience accessor to the country part (if any) of the locale
+    QLocale::Country country() const
+    {
+        return m_locale.country();
+    }
+
     /** @brief Get a Qt locale for the given @p localeName
      *
      * This special-cases `sr@latin`, which is used as a translation

src/libcalamares/locale/LabelModel.cpp

@@ -18,6 +18,8 @@
 
 #include "LabelModel.h"
 
+#include "Lookup.h"
+
 #include "CalamaresVersion.h"  // For the list of translations
 
 namespace CalamaresUtils::Locale
@@ -106,6 +108,19 @@ LabelModel::find( const QLocale& locale ) const
     } );
 }
 
+int
+LabelModel::find( const QString& countryCode ) const
+{
+    if ( countryCode.length() != 2 )
+        return -1;
+
+    auto c_l = countryData( countryCode );
+    int r = find( [&]( const Label& l ){ return ( l.language() == c_l.second ) && ( l.country() == c_l.first ); } );
+    if ( r >= 0 )
+        return r;
+    return find( [&]( const Label& l ){ return l.language() == c_l.second; } );
+}
+
 LabelModel* const availableTranslations()
 {
     static LabelModel model( QString( CALAMARES_TRANSLATION_LANGUAGES ).split( ';') );

src/libcalamares/locale/LabelModel.h

@@ -59,7 +59,10 @@ public:
      */
     int find( std::function<bool( const QLocale& )> predicate ) const;
     int find( std::function<bool( const Label& )> predicate ) const;
+    /// @brief Looks for an item using the same locale, -1 if there isn't one
     int find( const QLocale& ) const;
+    /// @brief Looks for an item that best matches the 2-letter country code
+    int find( const QString& countryCode ) const;
 
 private:
     QVector< Label > m_locales;