3 files changed, 22 insertions, 1 deletions
diff --git a/crawl-ref/source/dgnevent.cc b/crawl-ref/source/dgnevent.cc
index 0109c0090a..b0c24c5fb1 100644
--- a/crawl-ref/source/dgnevent.cc
+++ b/crawl-ref/source/dgnevent.cc
@@ -21,6 +21,23 @@ void dgn_event_dispatcher::clear()
             grid_triggers[x][y].reset(NULL);
 }
 
+void dgn_event_dispatcher::clear_listeners_at(const coord_def &pos)
+{
+    grid_triggers[pos.x][pos.y].reset(NULL);
+}
+
+void dgn_event_dispatcher::move_listeners(
+    const coord_def &from, const coord_def &to)
+{
+    // Any existing listeners at to will be discarded. YHBW.
+    grid_triggers[to.x][to.y] = grid_triggers[from.x][from.y];
+}
+
+bool dgn_event_dispatcher::has_listeners_at(const coord_def &pos) const
+{
+    return (grid_triggers[pos.x][pos.y].get());
+}
+
 void dgn_event_dispatcher::fire_position_event(
     dgn_event_type event, const coord_def &pos)
 {
diff --git a/crawl-ref/source/dgnevent.h b/crawl-ref/source/dgnevent.h
index efc5cdd59a..61134966b7 100644
--- a/crawl-ref/source/dgnevent.h
+++ b/crawl-ref/source/dgnevent.h
@@ -83,6 +83,9 @@ public:
     }
 
     void clear();
+    void clear_listeners_at(const coord_def &pos);
+    bool has_listeners_at(const coord_def &pos) const;
+    void move_listeners(const coord_def &from, const coord_def &to);
     
     void fire_position_event(dgn_event_type et, const coord_def &pos);
     void fire_event(dgn_event_type et);
diff --git a/crawl-ref/source/misc.cc b/crawl-ref/source/misc.cc
index 372dbebb84..d929e2b449 100644
--- a/crawl-ref/source/misc.cc
+++ b/crawl-ref/source/misc.cc
@@ -526,7 +526,7 @@ static bool is_critical_feature(dungeon_feature_type feat)
 
 static bool is_feature_shift_target(const coord_def &pos)
 {
-    return (grd(pos) == DNGN_FLOOR);
+    return (grd(pos) == DNGN_FLOOR && !dungeon_events.has_listeners_at(pos));
 }
 
 static bool dgn_shift_feature(const coord_def &pos)
@@ -550,6 +550,7 @@ static bool dgn_shift_feature(const coord_def &pos)
             }
         }
         env_move_markers(pos, dest);
+        dungeon_events.move_listeners(pos, dest);
 
         if (see_grid(dest) && is_notable_terrain(dfeat))
             seen_notable_thing(dfeat, dest.x, dest.y);