monster spellcasting fallthroughs

This changes monster spellcasting to remove the fallthroughs.  It simply loops
now until it finds a valid spell to cast, so if the spell is useless another
random spell is picked rather than falling through to whatever happens to be
the next one in the list.

This will inevitably change some spellcasting probabilities.

diff --git a/src/mcastu.c b/src/mcastu.c
index 921fb7aaf8146145d5c030b78587d30e2197e932..1ac8ff68151aca945e5307e078f71bcbfa350b3e 100644 (file)
--- a/src/mcastu.c
+++ b/src/mcastu.c
@@ -170,30 +170,39 @@ castmu(mtmp, mattk, thinks_it_foundyou, foundyou)
        int spellnum = 0;
 
        /* Three cases:
-        * -- monster is attacking you.  Cast spell normally.
-        * -- monster thinks it's attacking you.  Cast spell, but spells that
-        *    are not undirected fail with cursetxt() and loss of mspec_used.
-        * -- monster isn't trying to attack.  Cast spell; spells that are
-        *    are not undirected don't go off, but they don't fail--they're
-        *    just not cast.
+        * -- monster is attacking you.  Search for a useful spell.
+        * -- monster thinks it's attacking you.  Search for a useful spell,
+        *    without checking for undirected.  If the spell found is directed,
+        *    it fails with cursetxt() and loss of mspec_used.
+        * -- monster isn't trying to attack.  Select a spell once.  Don't keep
+        *    searching; if that spell is not useful (or if it's directed),
+        *    return and do something else. 
         * Since most spells are directed, this means that a monster that isn't
         * attacking casts spells only a small portion of the time that an
         * attacking monster does.
         */
        if (mattk->adtyp == AD_SPEL || mattk->adtyp == AD_CLRC) {
-           spellnum = rn2(ml);
-           if (mattk->adtyp == AD_SPEL)
-               spellnum = choose_magic_spell(spellnum);
-           else
-               spellnum = choose_clerical_spell(spellnum);
-           /* not trying to attack?  don't allow directed spells */
-           if (!thinks_it_foundyou &&
-                   (!is_undirected_spell(mattk->adtyp, spellnum) ||
-                   spell_would_be_useless(mtmp, mattk->adtyp, spellnum))) {
-               if (foundyou)
-                   impossible("spellcasting monster found you and doesn't know it?");
-               return 0;
-           }
+           int cnt = 40;
+
+           do {
+               spellnum = rn2(ml);
+               if (mattk->adtyp == AD_SPEL)
+                   spellnum = choose_magic_spell(spellnum);
+               else
+                   spellnum = choose_clerical_spell(spellnum);
+               /* not trying to attack?  don't allow directed spells */
+               if (!thinks_it_foundyou) {
+                   if (!is_undirected_spell(mattk->adtyp, spellnum) ||
+                       spell_would_be_useless(mtmp, mattk->adtyp, spellnum)) {
+                       if (foundyou)
+                           impossible("spellcasting monster found you and doesn't know it?");
+                       return 0;
+                   }
+                   break;
+               }
+           } while(--cnt > 0 &&
+                   spell_would_be_useless(mtmp, mattk->adtyp, spellnum));
+           if (cnt == 0) return 0;
        }
 
        /* monster unable to cast spells? */
@@ -302,7 +311,8 @@ castmu(mtmp, mattk, thinks_it_foundyou, foundyou)
 /*
    If dmg is zero, then the monster is not casting at you.
    If the monster is intentionally not casting at you, we have previously
-   called spell_would_be_useless() and the fallthroughs shouldn't happen.
+   called spell_would_be_useless() and spellnum should always be a valid
+   undirected spell.
    If you modify either of these, be sure to change is_undirected_spell()
    and spell_would_be_useless().
  */
@@ -342,9 +352,9 @@ int spellnum;
            pline("Double Trouble...");
            clonewiz();
            dmg = 0;
-           break;
-       }
-       /* else FALLTHRU */
+       } else
+           impossible("bad wizard cloning?");
+       break;
     case MGC_SUMMON_MONS:              /* also aggravates */
     {
        int count;
@@ -409,9 +419,9 @@ int spellnum;
                      !See_invisible ? "disappears" : "becomes transparent");
            mon_set_minvis(mtmp);
            dmg = 0;
-           break;
-       }
-       /* else FALLTHRU */
+       } else
+           impossible("no reason for monster to cast disappear spell?");
+       break;
     case MGC_STUN_YOU:
        if (Antimagic || Free_action) {
            shieldeff(u.ux, u.uy);
@@ -438,9 +448,8 @@ int spellnum;
            if ((mtmp->mhp += d(3,6)) > mtmp->mhpmax)
                mtmp->mhp = mtmp->mhpmax;
            dmg = 0;
-           break;
        }
-       /* else FALLTHRU */
+       break;
     case MGC_PSI_BOLT:
        /* prior to 3.4.0 Antimagic was setting the damage to 1--this
           made the spell virtually harmless to players with magic res. */
@@ -580,9 +589,9 @@ int spellnum;
            make_blinded(Half_spell_damage ? 100L : 200L, FALSE);
            if (!Blind) Your(vision_clears);
            dmg = 0;
-           break;
-       }
-       /* else FALLTHRU */
+       } else
+           impossible("no reason for monster to cast blindness spell?");
+       break;
     case CLC_PARALYZE:
        if (Antimagic || Free_action) {
            shieldeff(u.ux, u.uy);
@@ -623,9 +632,8 @@ int spellnum;
            if ((mtmp->mhp += d(3,6)) > mtmp->mhpmax)
                mtmp->mhp = mtmp->mhpmax;
            dmg = 0;
-           break;
        }
-       /* else FALLTHRU */
+       break;
     case CLC_OPEN_WOUNDS:
        if (Antimagic) {
            shieldeff(u.ux, u.uy);
@@ -679,9 +687,7 @@ int spellnum;
     return FALSE;
 }
 
-/* Some undirected spells are useless under some circumstances. */
-/* This isn't called when the monster is deliberately casting at you; we
-   handle that using fallthroughs. */
+/* Some spells are useless under some circumstances. */
 STATIC_DCL
 boolean
 spell_would_be_useless(mtmp, adtyp, spellnum)
@@ -721,6 +727,9 @@ int adtyp;
        if (!couldsee && (spellnum == MGC_SUMMON_MONS ||
                (!mtmp->iswiz && spellnum == MGC_CLONE_WIZ)))
            return TRUE;
+       if ((!mtmp->iswiz || flags.no_of_wizards > 1)
+                                               && spellnum == MGC_CLONE_WIZ)
+           return TRUE;
     } else if (adtyp == AD_CLRC) {
        /* summon insects/sticks to snakes won't be cast by peaceful monsters */
        if (mtmp->mpeaceful && spellnum == CLC_INSECTS)
@@ -731,6 +740,9 @@ int adtyp;
        /* don't summon insects if it doesn't think you're around */
        if (!couldsee && spellnum == CLC_INSECTS)
            return TRUE;
+       /* blindness spell on blinded player */
+       if (Blinded && spellnum == CLC_BLIND_YOU)
+           return TRUE;
     }
     return FALSE;
 }