From 0d9801e17f1c96a667baaa636e6224726e7e1679 Mon Sep 17 00:00:00 2001
From: PatR <rankin@nethack.org>
Date: Fri, 17 Mar 2023 16:21:43 -0700
Subject: [PATCH] vampshifting via polymorph

When a vampire that's already in bat or fog form gets polymorphed,
sometimes take on base vampire form instead of always toggling to
fog or bat.
---
 src/mon.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/mon.c b/src/mon.c
index 26f4d6031..68565164a 100644
--- a/src/mon.c
+++ b/src/mon.c
@@ -4325,7 +4325,7 @@ decide_to_shapeshift(struct monst *mon, int shiftflags)
 }
 
 static int
-pickvampshape(struct monst* mon)
+pickvampshape(struct monst *mon)
 {
     int mndx = mon->cham, wolfchance = 10;
     /* avoid picking monsters with lowercase display symbols ('d' for wolf
@@ -4350,7 +4350,11 @@ pickvampshape(struct monst* mon)
         break;
     }
 
-    if (gm.mvitals[mndx].mvflags & G_GENOD)
+    /* return to base form if chosen poly target has been genocided
+       or randomly if already in an alternate form (to prevent always
+       switching back and forth between bat and fog) */
+    if ((gm.mvitals[mndx].mvflags & G_GENOD) != 0
+        || (mon->data != &mons[mon->cham] && !rn2(4)))
         return mon->cham;
 
     return mndx;