[gnome-calculator] Use official unit from format instead of internal name (fixes #207)

[Robert Roth <robertroth src gnome org>]

commit d18e57a514baa03946a08751c418ed28866fe04f
Author: Robert Roth <robert roth off gmail com>
Date:   Wed Feb 24 00:58:32 2021 +0200

    Use official unit from format instead of internal name (fixes #207)

 lib/unit.vala           | 5 +++++
 src/math-converter.vala | 2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)
---
diff --git a/lib/unit.vala b/lib/unit.vala
index b214d0c4..c59b58dc 100644
--- a/lib/unit.vala
+++ b/lib/unit.vala
@@ -379,6 +379,11 @@ public class Unit : Object
             _symbols.append (symbol_name);
     }
 
+    public string get_symbol_from_format ()
+    {
+        return _format.replace ("%s", "").replace (" ", "");
+    }
+
     public bool matches_symbol (string symbol, bool case_sensitive = true)
     {
         foreach (var s in _symbols)
diff --git a/src/math-converter.vala b/src/math-converter.vala
index 9e4f8ed5..d0ae583d 100644
--- a/src/math-converter.vala
+++ b/src/math-converter.vala
@@ -248,7 +248,7 @@ public class MathConverter : Gtk.Grid
             var z = convert_equation (x, out from_unit, out to_unit);
             if (z != null && from_unit != null && to_unit != null)
             {
-                equation.set ("%s %s %s %s".printf(equation.serializer.to_string (x), from_unit.name, 
_("in"), to_unit.name));
+                equation.set ("%s %s %s %s".printf(equation.serializer.to_string (x), 
from_unit.get_symbol_from_format (), _("in"), to_unit.get_symbol_from_format ()));
                 equation.solve ();
             }
         }