I've just realised that the JS puzzles' permalinks were not updating

when the user pressed 'n' for a new game, because all the front end
knows is that it passed a keystroke to the puzzle, and it has no way
of hearing back that a particular keypress resulted in a game id
change.

To fix this, I've renamed midend_request_desc_changes to
midend_request_id_changes and expanded its remit to cover _any_ change
to the game ids. So now that callback in the Emscripten front end is
the only place from which update_permalinks is called (apart from
initialising them at setup time), and that should handle everything.

[originally from svn r9805]

devel.but

@@ -1609,10 +1609,6 @@ should use it if they're not Mines; if you think you need to use it,
 think again repeatedly in the hope of finding a better way to do
 whatever it was you needed to do.
 
-If a front end wants to be notified when this happens, it can ask the
-midend to do so by calling \cw{midend_request_desc_changes()}; see
-\k{midend-request-desc-changes}.
-
 \C{drawing} The drawing API
 
 The back end function \cw{redraw()} (\k{backend-redraw}) is required
@@ -3274,17 +3270,18 @@ message (which does not need freeing at all).
 accept or return a pointer to a midend. You'd probably call it just
 \e{before} deciding what kind of midend you wanted to instantiate.)
 
-\H{midend-request-desc-changes} \cw{midend_request_desc_changes()}
+\H{midend-request-id-changes} \cw{midend_request_id_changes()}
 
-\c void midend_request_desc_changes(midend *me,
+\c void midend_request_id_changes(midend *me,
 \c                                void (*notify)(void *), void *ctx);
 
 This function is called by the front end to request notification by
-the mid-end when a puzzle supersedes its game description (see
-\k{backend-supersede}). After this function is called, any call to
-\cw{midend_supersede_game_desc()} by the back end will cause the
-mid-end to call \cw{notify(ctx)} after the game description is
-changed.
+the mid-end when the current game IDs (either descriptive or
+random-seed) change. This can occur as a result of keypresses ('n' for
+New Game, for example) or when a puzzle supersedes its game
+description (see \k{backend-supersede}). After this function is
+called, any change of the game ids will cause the mid-end to call
+\cw{notify(ctx)} after the change.
 
 This is for use by puzzles which want to present the game description
 to the user constantly (e.g. as an HTML hyperlink) instead of only

emcc.c

@@ -313,10 +313,10 @@ static void update_permalinks(void)
 }
 
 /*
- * Callback from the midend if Mines supersedes its game description,
- * so we can update the permalinks.
+ * Callback from the midend when the game ids change, so we can update
+ * the permalinks.
  */
-static void desc_changed(void *ignored)
+static void ids_changed(void *ignored)
 {
     update_permalinks();
 }
@@ -598,7 +598,6 @@ static void cfg_end(int use_results)
             midend_new_game(me);
             resize();
             midend_redraw(me);
-            update_permalinks();
             free_cfg(cfg);
             js_dialog_cleanup();
         }
@@ -653,7 +652,6 @@ void command(int n)
                  */
                 midend_set_params(me, presets[i]);
                 midend_new_game(me);
-                update_permalinks();
                 resize();
                 midend_redraw(me);
                 update_undo_redo();
@@ -802,11 +800,11 @@ int main(int argc, char **argv)
     }
 
     /*
-     * Request notification if a puzzle (hopefully only ever Mines)
-     * supersedes its game description, so that we can proactively
-     * update the permalink.
+     * Request notification when the game ids change (e.g. if the user
+     * presses 'n', and also when Mines supersedes its game
+     * description), so that we can proactively update the permalink.
      */
-    midend_request_desc_changes(me, desc_changed, NULL);
+    midend_request_id_changes(me, ids_changed, NULL);
 
     /*
      * Draw the puzzle's initial state, and set up the permalinks and

midend.c

@@ -82,8 +82,8 @@ struct midend {
 
     int preferred_tilesize, tilesize, winwidth, winheight;
 
-    void (*game_desc_change_notify_function)(void *);
-    void *game_desc_change_notify_ctx;
+    void (*game_id_change_notify_function)(void *);
+    void *game_id_change_notify_ctx;
 };
 
 #define ensure(me) do { \
@@ -499,6 +499,9 @@ void midend_new_game(midend *me)
     me->ui = me->ourgame->new_ui(me->states[0].state);
     midend_set_timer(me);
     me->pressed_mouse_button = 0;
+
+    if (me->game_id_change_notify_function)
+        me->game_id_change_notify_function(me->game_id_change_notify_ctx);
 }
 
 int midend_can_undo(midend *me)
@@ -1082,10 +1085,10 @@ int midend_wants_statusbar(midend *me)
     return me->ourgame->wants_statusbar;
 }
 
-void midend_request_desc_changes(midend *me, void (*notify)(void *), void *ctx)
+void midend_request_id_changes(midend *me, void (*notify)(void *), void *ctx)
 {
-    me->game_desc_change_notify_function = notify;
-    me->game_desc_change_notify_ctx = ctx;
+    me->game_id_change_notify_function = notify;
+    me->game_id_change_notify_ctx = ctx;
 }
 
 void midend_supersede_game_desc(midend *me, char *desc, char *privdesc)
@@ -1094,8 +1097,8 @@ void midend_supersede_game_desc(midend *me, char *desc, char *privdesc)
     sfree(me->privdesc);
     me->desc = dupstr(desc);
     me->privdesc = privdesc ? dupstr(privdesc) : NULL;
-    if (me->game_desc_change_notify_function)
-        me->game_desc_change_notify_function(me->game_desc_change_notify_ctx);
+    if (me->game_id_change_notify_function)
+        me->game_id_change_notify_function(me->game_id_change_notify_ctx);
 }
 
 config_item *midend_get_config(midend *me, int which, char **wintitle)

puzzles.h

@@ -268,8 +268,7 @@ char *midend_deserialise(midend *me,
                          void *rctx);
 char *identify_game(char **name, int (*read)(void *ctx, void *buf, int len),
                     void *rctx);
-void midend_request_desc_changes(midend *me, void (*notify)(void *),
-                                 void *ctx);
+void midend_request_id_changes(midend *me, void (*notify)(void *), void *ctx);
 /* Printing functions supplied by the mid-end */
 char *midend_print_puzzle(midend *me, document *doc, int with_soln);
 int midend_tilesize(midend *me);