Refactor layout code, rescale and reformat when changing level

eek/eek-keyboard.h

@@ -62,6 +62,7 @@ struct _EekKeyboard
     struct xkb_keymap *keymap;
     int keymap_fd; // keymap formatted as XKB string
     size_t keymap_len; // length of the data inside keymap_fd
+    double scale;
 
     EekboardContextService *manager; // unowned reference
 };