CS115: Huge monsters stop drawbridges from closing

Only real change with this commit is the slightly more informative
message when the drawbridge is blocked.

I wanted m in close_drawbridge to be const, but mhis doesn't like it,
even though it doesn't modify its input. The code still needs more
const, at least for function inputs.

libnitrohack/include/extern.h

@@ -143,7 +143,7 @@ extern boolean is_db_wall(int,int);
 extern boolean find_drawbridge(int *,int*);
 extern boolean create_drawbridge(struct level *lev, int x, int y, int dir, boolean flag);
 extern void open_drawbridge(int,int);
-extern void close_drawbridge(int,int);
+extern boolean close_drawbridge(int,int);
 extern void destroy_drawbridge(int,int);
 
 /* ### decl.c ### */

libnitrohack/include/mondata.h

@@ -6,6 +6,7 @@
 
 #define verysmall(ptr)		((ptr)->msize < MZ_SMALL)
 #define bigmonst(ptr)		((ptr)->msize >= MZ_LARGE)
+#define hugemonst(ptr)		((ptr)->msize >= MZ_HUGE)
 
 #define pm_resistance(ptr,typ)	(((ptr)->mresists & (typ)) != 0)
 

libnitrohack/src/dbridge.c

@@ -589,19 +589,28 @@ static void do_entity(struct entity *etmp)
 }
 
 /*
- * Close the drawbridge located at x,y
+ * Close the drawbridge located at x,y.
+ * Returns TRUE if the drawbridge was closed, FALSE otherwise.
  */
-void close_drawbridge(int x, int y)
+boolean close_drawbridge(int x, int y)
 {
 	struct rm *loc1, *loc2;
+	struct monst *m;
 	struct trap *t;
 	int x2, y2;
 
 	loc1 = &level->locations[x][y];
-	if (loc1->typ != DRAWBRIDGE_DOWN) return;
+	if (loc1->typ != DRAWBRIDGE_DOWN) return FALSE;
+	/* A huge monster will block the drawbridge. */
+	if ((m = m_at(level, x, y)) && hugemonst(m->data)) {
+	    pline("%s blocks the drawbridge with %s weight!",
+		  canseemon(m) ? Amonnam(m) : "Something",
+		  canseemon(m) ? mhis(m) : "its");
+	    return FALSE;
+	}
 	if (rn2(5) == 0) {
 	    pline("The mechanism seems to have something stuck in it and won't close.");
-	    return;
+	    return FALSE;
 	}
 	x2 = x; y2 = y;
 	get_wall_for_db(&x2,&y2);
@@ -639,6 +648,7 @@ void close_drawbridge(int x, int y)
 	newsym(x, y);
 	newsym(x2, y2);
 	block_point(x2,y2);	/* vision */
+	return TRUE;
 }
 
 /*

libnitrohack/src/zap.c

@@ -2624,7 +2624,12 @@ struct monst *beam_hit(int ddx, int ddy, int range,	/* direction and range */
 			if ((cansee(x,y) || cansee(bhitpos.x, bhitpos.y))
 			    && level->locations[x][y].typ == DRAWBRIDGE_DOWN)
 			    makeknown(obj->otyp);
-			close_drawbridge(x,y);
+			if (!close_drawbridge(x, y)) {
+			    /* Stop the ray to prevent a door being made
+			     * in the drawbridge's doorway.
+			     */
+			    return NULL;
+			}
 			break;
 		    case WAN_STRIKING:
 		    case SPE_FORCE_BOLT: