Make encode_ui() and decode_ui() optional in back-ends

The majority of back-ends define encode_ui() to return NULL and
decode_ui() to do nothing.  This commit allows them to instead specify
the relevant function pointers as NULL, in which case the mid-end won't
try to call them.

I'm planning to add a parameter to decode_ui(), and if I'm going to have
to touch every back-end's version of decode_ui(), I may as well ensure
that most of them never need to be touched again.  And obviously
encode_ui() should go the same way for symmetry.

1 files changed, 2 insertions, 13 deletions

diff --git a/lightup.c b/lightup.c
index 35705a6..f60017f 100644
--- a/lightup.c
+++ b/lightup.c
@@ -1848,17 +1848,6 @@ static void free_ui(game_ui *ui)
     sfree(ui);
 }
 
-static char *encode_ui(const game_ui *ui)
-{
-    /* nothing to encode. */
-    return NULL;
-}
-
-static void decode_ui(game_ui *ui, const char *encoding)
-{
-    /* nothing to decode. */
-}
-
 static void game_changed_state(game_ui *ui, const game_state *oldstate,
                                const game_state *newstate)
 {
@@ -2343,8 +2332,8 @@ const struct game thegame = {
     true, game_can_format_as_text_now, game_text_format,
     new_ui,
     free_ui,
-    encode_ui,
-    decode_ui,
+    NULL, /* encode_ui */
+    NULL, /* decode_ui */
     NULL, /* game_request_keys */
     game_changed_state,
     current_key_label,