Remove throwing net degradation, instead mulch probabilistically

Instead of throwing nets accumulating persistent damage as monsters
struggled against them (and then becoming impossible to stack in
your inventory afterward), they are either outright destroyed by
the struggle or remain in normal condition. This should make them
a little less cumbersome to use.

This commit doesn't actually touch any of the escape formulas (which
are an impressive snarl that could definitely use tending to), since
probably they would need rewriting from scratch and I didn't want to
undertake that so close to 0.14, with various other things still in
the air.

1 files changed, 20 insertions, 3 deletions

diff --git a/crawl-ref/source/traps.cc b/crawl-ref/source/traps.cc
index 8671563b74..270b529c91 100644
--- a/crawl-ref/source/traps.cc
+++ b/crawl-ref/source/traps.cc
@@ -436,7 +436,7 @@ void check_net_will_hold_monster(monster* mons)
     {
         const int net = get_trapping_net(mons->pos());
         if (net != NON_ITEM)
-            remove_item_stationary(mitm[net]);
+            free_stationary_net(net);
 
         if (mons->is_insubstantial())
         {
@@ -1409,7 +1409,7 @@ void free_self_from_net()
             you.attribute[ATTR_HELD] = 0;
             you.redraw_quiver = true;
             you.redraw_evasion = true;
-            remove_item_stationary(mitm[net]);
+            free_stationary_net(net);
             return;
         }
 
@@ -1422,6 +1422,23 @@ void free_self_from_net()
     }
 }
 
+void free_stationary_net(int item_index)
+{
+    item_def &item = mitm[item_index];
+    if (item.base_type == OBJ_MISSILES && item.sub_type == MI_THROWING_NET)
+    {
+        // Probabilistically mulch net based on damage done, otherwise
+        // reset damage counter (ie: item.plus).
+        if (x_chance_in_y(-item.plus, 9))
+            destroy_item(item_index);
+        else
+        {
+            item.plus = 0;
+            item.plus2 = 0;
+        }
+    }
+}
+
 void clear_trapping_net()
 {
     if (!you.attribute[ATTR_HELD])
@@ -1432,7 +1449,7 @@ void clear_trapping_net()
 
     const int net = get_trapping_net(you.pos());
     if (net != NON_ITEM)
-        remove_item_stationary(mitm[net]);
+        free_stationary_net(net);
 
     you.attribute[ATTR_HELD] = 0;
     you.redraw_quiver = true;