fix #2495 - light vs gremlins (trunk only)

From a bug report, flashing yourself
with a camera while in gremlin form blinded as with any other form, but
didn't inflict any damage the way that flashing a monster gremlin does.
This fixes that, and also makes light from wand/scroll/spell that hits
you-as-gremlin or monster gremlins do 1d5 damage too.  It happens even
if the target is already in a lit spot, but doesn't continue afterwards:
simply being in a lit spot doesn't cause any damage, nor does lamp light.

src/read.c

@@ -1158,6 +1158,9 @@ struct obj *sobj; /* scroll, or fake spellbook object for scroll-like spell */
 		if (!confused || rn2(5)) {
 			if(!Blind) known = TRUE;
 			litroom(!confused && !scursed, sobj);
+			if (!confused && !scursed) {
+			    if (lightdamage(sobj, TRUE, 5)) known = TRUE;
+			}
 		} else {
 		   /* could be scroll of create monster, don't set known ...*/
 		    (void) create_critters(1, !scursed ?
@@ -1518,6 +1521,14 @@ int chg;		/* recharging */
     exercise(A_STR, FALSE);
 }
 
+/* used to collect gremlins being hit by light so that they can be processed
+   after vision for the entire lit area has been brought up to date */
+struct litmon {
+    struct monst *mon;
+    struct litmon *nxt;
+};
+STATIC_VAR struct litmon *gremlins = 0;
+
 /*
  * Low-level lit-field update routine.
  */
@@ -1526,9 +1537,18 @@ set_lit(x,y,val)
 int x, y;
 genericptr_t val;
 {
-	if (val)
+	struct monst *mtmp;
+	struct litmon *gremlin;
+
+	if (val) {
 	    levl[x][y].lit = 1;
-	else {
+	    if ((mtmp = m_at(x, y)) != 0 && mtmp->data == &mons[PM_GREMLIN]) {
+		gremlin = (struct litmon *)alloc(sizeof *gremlin);
+		gremlin->mon = mtmp;
+		gremlin->nxt = gremlins;
+		gremlins = gremlin;
+	    }
+	} else {
 	    levl[x][y].lit = 0;
 	    snuff_light_source(x, y);
 	}
@@ -1627,6 +1647,20 @@ do_it:
 	}
 
 	vision_full_recalc = 1;	/* delayed vision recalculation */
+	if (gremlins) {
+	    struct litmon *gremlin;
+
+	    /* can't delay vision recalc after all */
+	    vision_recalc(0);
+	    /* after vision has been updated, monsters who are affected
+	       when hit by light can now be hit by it */
+	    do {
+		gremlin = gremlins;
+		gremlins = gremlin->nxt;
+		light_hits_gremlin(gremlin->mon, rnd(5));
+		free((genericptr_t)gremlin);
+	    } while (gremlins);
+	}
 }
 
 STATIC_OVL void

src/uhitm.c

@@ -2609,16 +2609,7 @@ struct obj *otmp;	/* source of flash */
 		    /* Rule #1: Keep them out of the light. */
 		    amt = otmp->otyp == WAN_LIGHT ? d(1 + otmp->spe, 4) :
 		          rn2(min(mtmp->mhp,4));
-		    pline("%s %s!", Monnam(mtmp), amt > mtmp->mhp / 2 ?
-			  "wails in agony" : "cries out in pain");
-		    if ((mtmp->mhp -= amt) <= 0) {
-			if (context.mon_moving)
-			    monkilled(mtmp, (char *)0, AD_BLND);
-			else
-			    killed(mtmp);
-		    } else if (cansee(mtmp->mx,mtmp->my) && !canspotmon(mtmp)){
-			map_invisible(mtmp->mx, mtmp->my);
-		    }
+		    light_hits_gremlin(mtmp, amt);
 		}
 		if (mtmp->mhp > 0) {
 		    if (!context.mon_moving) setmangry(mtmp);
@@ -2632,4 +2623,21 @@ struct obj *otmp;	/* source of flash */
 	return res;
 }
 
+void
+light_hits_gremlin(mon, dmg)
+struct monst *mon;
+int dmg;
+{
+    pline("%s %s!", Monnam(mon),
+	  (dmg > mon->mhp / 2) ? "wails in agony" : "cries out in pain");
+    if ((mon->mhp -= dmg) <= 0) {
+	if (context.mon_moving)
+	    monkilled(mon, (char *)0, AD_BLND);
+	else
+	    killed(mon);
+    } else if (cansee(mon->mx, mon->my) && !canspotmon(mon)) {
+	map_invisible(mon->mx, mon->my);
+    }
+}
+
 /*uhitm.c*/

src/zap.c

@@ -1963,6 +1963,7 @@ register struct obj *obj;
 		case SPE_LIGHT:
 			litroom(TRUE,obj);
 			if (!Blind) known = TRUE;
+			if (lightdamage(obj, TRUE, 5)) known = TRUE;
 			break;
 		case WAN_SECRET_DOOR_DETECTION:
 		case SPE_DETECT_UNSEEN:
@@ -2279,7 +2280,9 @@ boolean ordinary;
 		    damage = d(obj->spe, 25);
 #ifdef TOURIST
 		case EXPENSIVE_CAMERA:
+		    if (!damage) damage = 5;
 #endif
+		    damage = lightdamage(obj, ordinary, damage);
 		    damage += rnd(25);
 		    if (flashburn((long)damage)) learn_it = TRUE;
 		    damage = 0;	/* reset */
@@ -2377,6 +2380,38 @@ struct attack *mattk;
 	zhitu(dtyp, mattk->damn, fltxt, u.ux, u.uy);
 }
 
+/* light damages hero in gremlin form */
+int
+lightdamage(obj, ordinary, amt)
+struct obj *obj;	/* item making light (fake book if spell) */
+boolean ordinary;	/* wand/camera zap vs wand destruction */
+int amt;	/* pseudo-damage used to determine blindness duration */
+{
+    char buf[BUFSZ];
+    const char *how;
+    int dmg = amt;
+
+    if (dmg && youmonst.data == &mons[PM_GREMLIN]) {
+	/* reduce high values (from destruction of wand with many charges) */
+	dmg = rnd(dmg);
+	if (dmg > 10) dmg = 10 + rnd(dmg - 10);
+	if (dmg > 20) dmg = 20;
+	pline("Ow, that light hurts%c", (dmg > 2 || u.mh <= 5) ? '!' : '.');
+	/* [composing killer/reason is superfluous here; if fatal, cause
+	   of death will always be "killed while stuck in creature form"] */
+	if (obj->oclass == SCROLL_CLASS || obj->oclass == SPBOOK_CLASS)
+	    ordinary = FALSE;	/* say blasted rather than zapped */
+	how = (obj->oclass != SPBOOK_CLASS) ?
+		(const char *)ansimpleoname(obj) : "spell of light";
+	Sprintf(buf, "%s %sself with %s",
+		ordinary ? "zapped" : "blasted", uhim(), how);
+	/* might rehumanize(); could be fatal, but only for Unchanging */
+	losehp(Maybe_Half_Phys(dmg), buf, NO_KILLER_PREFIX);
+    }
+    return dmg;
+}
+
+/* light[ning] causes blindness */
 boolean
 flashburn(duration)
 long duration;