2 files changed, 25 insertions, 8 deletions

diff --git a/crawl-ref/source/clua.cc b/crawl-ref/source/clua.cc
index d750fc9f09..8506d5d143 100644
--- a/crawl-ref/source/clua.cc
+++ b/crawl-ref/source/clua.cc
@@ -467,12 +467,13 @@ bool CLua::calltopfn(lua_State *ls, const char *params, va_list args,
     return (!err);
 }
 
-bool CLua::callbooleanfn(bool def, const char *fn, const char *params, ...)
+maybe_bool CLua::callmbooleanfn(const char *fn, const char *params,
+                                const va_list *args)
 {
     error.clear();
     lua_State *ls = state();
     if (!ls)
-        return (def);
+        return (B_MAYBE);
 
     int stacktop = lua_gettop(ls);
 
@@ -480,17 +481,30 @@ bool CLua::callbooleanfn(bool def, const char *fn, const char *params, ...)
     if (!lua_isfunction(ls, -1))
     {
         lua_pop(ls, 1);
-        CL_RESETSTACK_RETURN(ls, stacktop, def);
+        CL_RESETSTACK_RETURN(ls, stacktop, B_MAYBE);
     }
 
+    bool ret = calltopfn(ls, params, *args, 1);
+    if (!ret)
+        CL_RESETSTACK_RETURN(ls, stacktop, B_MAYBE);
+
+    maybe_bool r = frombool(lua_toboolean(ls, -1));
+    CL_RESETSTACK_RETURN(ls, stacktop, r);
+}
+
+maybe_bool CLua::callmbooleanfn(const char *fn, const char *params, ...)
+{
     va_list args;
     va_start(args, params);
-    bool ret = calltopfn(ls, params, args, 1);
-    if (!ret)
-        CL_RESETSTACK_RETURN(ls, stacktop, def);
+    return (callmbooleanfn(fn, params, &args));
+}
 
-    def = lua_toboolean(ls, -1);
-    CL_RESETSTACK_RETURN(ls, stacktop, def);
+bool CLua::callbooleanfn(bool def, const char *fn, const char *params, ...)
+{
+    va_list args;
+    va_start(args, params);
+    maybe_bool r = callmbooleanfn(fn, params, &args);
+    return (tobool(r, def));
 }
 
 bool CLua::proc_returns(const char *par) const
diff --git a/crawl-ref/source/clua.h b/crawl-ref/source/clua.h
index 1bbf70c720..6877c47a18 100644
--- a/crawl-ref/source/clua.h
+++ b/crawl-ref/source/clua.h
@@ -128,6 +128,7 @@ public:
 
     void pushglobal(const std::string &name);
 
+    maybe_bool callmbooleanfn(const char *fn, const char *params, ...);
     bool callbooleanfn(bool defval, const char *fn, const char *params, ...);
     bool callfn(const char *fn, int nargs, int nret = 1);
     bool callfn(const char *fn, const char *params, ...);
@@ -189,6 +190,8 @@ private:
 
     bool calltopfn(lua_State *ls, const char *format, va_list args,
                    int retc = -1, va_list *fnr = NULL);
+    maybe_bool callmbooleanfn(const char *fn, const char *params,
+                              const va_list *args);
 
     int push_args(lua_State *ls, const char *format, va_list args,
                     va_list *cpto = NULL);