iron balls/teleds

Fixing some iron ball/teleds stuff:
-- If the player can pass through walls, ignore all checks for walls, or else
things will behave weirdly.
-- Instead of using the kludge "if the distance is >2 it must be a teleport",
pass a parameter indicating whether they crawled or teleported onto the new
space.  This fixes a special case, where the player moved one space and the
ball didn't move, but the chain moved through solid rock.  This is acceptable
if teleporting and unacceptable if dragging.
This also required some rearrangement of teleds() so that u.ux,u.uy
are set after placing the ball, not before.  I'm still not sure the pit
filling line is in the right place; anyone know?
-- add some comments so I can look at the code in a month and still know what
I did.
Most of this patch is just adding the new parameter.

src/teleport.c

@@ -201,34 +201,50 @@ boolean trapok;
 }
 
 void
-teleds(nux, nuy)
+teleds(nux, nuy, allow_drag)
 register int nux,nuy;
+boolean allow_drag;
 {
-	boolean dont_teleport_ball = FALSE;
+	boolean ball_still_in_range = FALSE;
 
+	/* If they have to move the ball, then drag if allow_drag is true;
+	 * otherwise they are teleporting, so unplacebc().  
+	 * If they don't have to move the ball, then always "drag" whether or
+	 * not allow_drag is true, because we are calling that function, not
+	 * to drag, but to move the chain.  *However* there are some dumb
+	 * special cases:
+	 *    0				 0
+	 *   _X  move east       ----->  X_
+	 *    @				  @
+	 * These are permissible if teleporting, but not if dragging.  As a
+	 * result, drag_ball() needs to know about allow_drag and might end
+	 * up dragging the ball anyway.  Also, drag_ball() might find that
+	 * dragging the ball is completely impossible (ball in range but there's
+	 * rock in the way), in which case it teleports the ball on its own.
+	 */
 	if (Punished) {
-	    /* If they're teleporting to a position where the ball doesn't need
-	     * to be moved, don't place the ball.  Especially useful when this
-	     * function is being called for crawling out of water instead of
-	     * real teleportation.
-	     */
 	    if (!carried(uball) && distmin(nux, nuy, uball->ox, uball->oy) <= 2)
-		dont_teleport_ball = TRUE;
-	    else
-		unplacebc();
+		ball_still_in_range = TRUE; /* don't have to move the ball */
+	    else {
+		/* have to move the ball */
+		if (!allow_drag || distmin(u.ux, u.uy, nux, nuy) > 1) {
+		    /* we should not have dist > 1 and allow_drag at the same
+		     * time, but just in case, we must then revert to teleport.
+		     */
+		    allow_drag = FALSE;
+		    unplacebc();
+		}
+	    }
 	}
 	u.utrap = 0;
 	u.ustuck = 0;
 	u.ux0 = u.ux;
 	u.uy0 = u.uy;
-	u.ux = nux;
-	u.uy = nuy;
-	fill_pit(u.ux0, u.uy0); /* do this now so that cansee() is correct */
 
 	if (hides_under(youmonst.data))
 		u.uundetected = OBJ_AT(nux, nuy);
 	else if (youmonst.data->mlet == S_EEL)
-		u.uundetected = is_pool(u.ux, u.uy);
+		u.uundetected = is_pool(nux, nuy);
 	else {
 		u.uundetected = 0;
 		/* mimics stop being unnoticed */
@@ -241,25 +257,24 @@ register int nux,nuy;
 		docrt();
 	}
 	if (Punished) {
-	    if (dont_teleport_ball) {
+	    if (ball_still_in_range || allow_drag) {
 		int bc_control;
 		xchar ballx, bally, chainx, chainy;
 		boolean cause_delay;
 
-		/* We really should only be dragging the chain here, since we
-		 * checked the ball distance.  However, some pathological
-		 * cases will drag the ball anyway.  drag_ball() tries to
-		 * handle those by ignoring near_capacity() and teleporting the
-		 * ball and chain along with you.  Bug: if you only teleported
-		 * one square, drag_ball() has no way to distinguish between
-		 * teleporting and moving, and treats it like a move.  (Note
-		 * that teleds() doesn't imply teleporting.)
-		 */
-		if (drag_ball(u.ux, u.uy, &bc_control, &ballx, &bally,
-					&chainx, &chainy, &cause_delay))
+		if (drag_ball(nux, nuy, &bc_control, &ballx, &bally,
+				    &chainx, &chainy, &cause_delay, allow_drag))
 		    move_bc(0, bc_control, ballx, bally, chainx, chainy);
-	    } else
-		 placebc();
+	    }
+	}
+	/* must set u.ux, u.uy after drag_ball(), which may need to know
+	   the old position if allow_drag is true... */
+	u.ux = nux;
+	u.uy = nuy;
+	fill_pit(u.ux0, u.uy0);
+	if (Punished) {
+	    if (!ball_still_in_range && !allow_drag)
+		placebc();
 	}
 	initrack(); /* teleports mess up tracking monsters without this */
 	update_player_regions();
@@ -286,7 +301,8 @@ register int nux,nuy;
 }
 
 boolean
-safe_teleds()
+safe_teleds(allow_drag)
+boolean allow_drag;
 {
 	register int nux, nuy, tcnt = 0;
 
@@ -296,7 +312,7 @@ safe_teleds()
 	} while (!teleok(nux, nuy, (boolean)(tcnt > 200)) && ++tcnt <= 400);
 
 	if (tcnt <= 400) {
-		teleds(nux, nuy);
+		teleds(nux, nuy, allow_drag);
 		return TRUE;
 	} else
 		return FALSE;
@@ -309,7 +325,7 @@ vault_tele()
 	coord c;
 
 	if (croom && somexy(croom, &c) && teleok(c.x,c.y,FALSE)) {
-		teleds(c.x,c.y);
+		teleds(c.x,c.y,FALSE);
 		return;
 	}
 	tele();
@@ -394,14 +410,14 @@ tele()
 		    /* possible extensions: introduce a small error if
 		       magic power is low; allow transfer to solid rock */
 		    if (teleok(cc.x, cc.y, FALSE)) {
-			teleds(cc.x, cc.y);
+			teleds(cc.x, cc.y, FALSE);
 			return;
 		    }
 		    pline("Sorry...");
 		}
 	}
 
-	(void) safe_teleds();
+	(void) safe_teleds(FALSE);
 }
 
 int