Place carrion below movable items in item stacks

Since we don't reveal items under the top of a pile at a location that
hasn't been visited or has had its contents change, we can't have
apport target the first movable item without leaking information. This
commit prevents newly created carrion from blocking apport by always
placing it below the first movable item, if any.

1 files changed, 48 insertions, 8 deletions

diff --git a/crawl-ref/source/items.cc b/crawl-ref/source/items.cc
index b5fb810b56..fe4e72acb0 100644
--- a/crawl-ref/source/items.cc
+++ b/crawl-ref/source/items.cc
@@ -129,9 +129,31 @@ void link_items()
             continue;
         }
 
-        // link to top
-        mitm[i].link = igrd(mitm[i].pos);
-        igrd(mitm[i].pos) = i;
+        bool move_below = item_is_stationary(mitm[i])
+            && !item_is_stationary_net(mitm[i]);
+        int movable_ind = -1;
+        // Stationary item, find index at location
+        if (move_below)
+        {
+
+            for (stack_iterator si(mitm[i].pos); si; ++si)
+            {
+                if (!item_is_stationary(*si) || item_is_stationary_net(*si))
+                    movable_ind = si->index();
+            }
+        }
+        // Link to top
+        if (!move_below || movable_ind == -1)
+        {
+            mitm[i].link = igrd(mitm[i].pos);
+            igrd(mitm[i].pos) = i;
+        }
+        // Link below movable items.
+        else
+        {
+            mitm[i].link = mitm[movable_ind].link;
+            mitm[movable_ind].link = i;
+        }
     }
 }
 
@@ -1903,11 +1925,13 @@ bool move_item_to_grid(int *const obj, const coord_def& p, bool silent)
     ASSERT_IN_BOUNDS(p);
 
     int& ob(*obj);
+
     // Must be a valid reference to a valid object.
     if (ob == NON_ITEM || !mitm[ob].defined())
         return false;
 
     item_def& item(mitm[ob]);
+    bool move_below = item_is_stationary(item) && !item_is_stationary_net(item);
 
     if (feat_destroys_item(grd(p), mitm[ob], !silenced(p) && !silent))
     {
@@ -1924,8 +1948,9 @@ bool move_item_to_grid(int *const obj, const coord_def& p, bool silent)
         maybe_identify_base_type(item);
     }
 
-    // If it's a stackable type...
-    if (is_stackable_item(item))
+    // If it's a stackable type or stationary item that's not a net...
+    int movable_ind = -1;
+    if (move_below || is_stackable_item(item))
     {
         // Look for similar item to stack:
         for (stack_iterator si(p); si; ++si)
@@ -1945,6 +1970,11 @@ bool move_item_to_grid(int *const obj, const coord_def& p, bool silent)
                 _gozag_move_gold_to_top(p);
                 return true;
             }
+            if (move_below
+                && (!item_is_stationary(*si) || item_is_stationary_net(*si)))
+            {
+                movable_ind = si->index();
+            }
         }
     }
     // Non-stackable item that's been fudge-stacked (monster throwing weapons).
@@ -1971,9 +2001,19 @@ bool move_item_to_grid(int *const obj, const coord_def& p, bool silent)
     // Move item to coord.
     item.pos = p;
 
-    // Link item to top of list.
-    item.link = igrd(p);
-    igrd(p) = ob;
+    // Need to move this stationary item to the position in the pile
+    // below the lowest non-stationary, non-net item.
+    if (move_below && movable_ind >= 0)
+    {
+        item.link = mitm[movable_ind].link;
+        mitm[movable_ind].link = item.index();
+    }
+    // Movable item or no movable items in pile, link item to top of list.
+    else
+    {
+        item.link = igrd(p);
+        igrd(p) = ob;
+    }
 
     if (item_is_orb(item))
         env.orb_pos = p;