make font settings cross platform

src/gui/salemodel.cpp

@@ -5,6 +5,7 @@
 #include <algorithm>
 
 #include <QFont>
+#include <QFontDatabase>
 
 SaleModel::SaleModel(Marketplace* market, QObject* parent) : QAbstractItemModel(parent)
 {
@@ -83,8 +84,7 @@ QVariant SaleModel::data(const QModelIndex& index, int role) const
         case 0:
             return myFont;
         case 1:
-            myFont.setFamily("monospace");
-            return myFont;
+            return QFontDatabase::systemFont(QFontDatabase::FixedFont);
         default:
             return myFont;
         }