Allow mon-pick to be used with arbitrary pop_entry lists

The pick_monster_from function can now be called with a pop_entry
table and a depth to allow reuse of the mon-pick algorithm
in other situations (e.g. spawn lists for summoning effects).

1 files changed, 20 insertions, 0 deletions

diff --git a/crawl-ref/source/mon-pick.h b/crawl-ref/source/mon-pick.h
index 55383463d5..47ddce1755 100644
--- a/crawl-ref/source/mon-pick.h
+++ b/crawl-ref/source/mon-pick.h
@@ -11,12 +11,32 @@
 
 #define DEPTH_NOWHERE 999
 
+enum distrib_type
+{
+    FLAT, // full chance throughout the range
+    SEMI, // 50% chance at range ends, 100% in the middle
+    PEAK, // 0% chance just outside range ends, 100% in the middle, range
+          // ends typically get ~20% or more
+    UP,   // linearly from near-zero to 100%, increasing with depth
+    DOWN, // linearly from 100% at the start to near-zero
+};
+
+typedef struct
+{
+    int minr;
+    int maxr;
+    int rarity; // 0..1000
+    distrib_type distrib;
+    monster_type mons;
+} pop_entry;
+
 typedef bool (*mon_pick_vetoer)(monster_type);
 
 int mons_rarity(monster_type mcls, branch_type branch);
 int mons_depth(monster_type mcls, branch_type branch);
 
 monster_type pick_monster(level_id place, mon_pick_vetoer veto = nullptr);
+monster_type pick_monster_from(const pop_entry *fpop, int depth, mon_pick_vetoer veto = nullptr);
 monster_type pick_monster_no_rarity(branch_type branch);
 monster_type pick_monster_by_hash(branch_type branch, uint32_t hash);
 monster_type pick_monster_all_branches(int absdepth0, mon_pick_vetoer veto = nullptr);