fix #2242 and #2292 - levitation exceptions (trunk only)

From a bug report.  The first report complained about levitation
allowing you to move through water on the Plane of Water, something that's
come up in the newsgroup lots of times (mostly about how levitation is
the best way to get around, only occasionally wondering why it works:
water walking doesn't work there because there's no surface, so where are
you levitating such that you're kept dry?)  The second report complained
about being told you were floating up if you put on a ring of levitation
while stuck inside a wall (perhaps after being stranded when polymorph
into xorn form ended).

     This implements intrinsic blocking for levitation and also for
flying.  Being inside solid rock (or closed door) anywhere and being in
water on the Plane of Water are the things that do it for levitation;
those two and levitating are what do it for flying.  Entering such
terrain turns off ability to float/fly, and leaving there turns it back
on; starting levitation blocks flight, ending it unblocks (levitation
has always overridden flying's ability to reach the floor).  Being able
to phase through rock doesn't prevent levitation and flight from being
blocked while in rock; you aren't floating or flying in that situation.

doc/fixes35.0

@@ -392,6 +392,8 @@ if hero was blind, killing the vault guard while in his temporary corridor
 	would leave hero encased in solid rock without informing player
 if hero dragged iron ball into temporary corridor and then killed vault guard,
 	the portion of corridor currently in existence would become permanent
+on Plane of Water, restrict levitation and flying to air bubbles;
+	elsewhere, restrict them such that they don't work inside solid rock
 
 
 Platform- and/or Interface-Specific Fixes

include/youprop.h

@@ -217,7 +217,8 @@
 
 #define HLevitation		u.uprops[LEVITATION].intrinsic
 #define ELevitation		u.uprops[LEVITATION].extrinsic
-#define Levitation		(HLevitation || ELevitation)
+#define BLevitation		u.uprops[LEVITATION].blocked
+#define Levitation		((HLevitation || ELevitation) && !BLevitation)
 	/* Can't touch surface, can't go under water; overrides all others */
 #define Lev_at_will		(((HLevitation & I_SPECIAL) != 0L || \
 				 (ELevitation & W_ARTI) != 0L) && \
@@ -226,11 +227,13 @@
 
 #define HFlying			u.uprops[FLYING].intrinsic
 #define EFlying			u.uprops[FLYING].extrinsic
+#define BFlying			u.uprops[FLYING].blocked
 #ifdef STEED
-# define Flying			(HFlying || EFlying || \
-				 (u.usteed && is_flyer(u.usteed->data)))
+# define Flying			((HFlying || EFlying || \
+				  (u.usteed && is_flyer(u.usteed->data))) && \
+				 !BFlying)
 #else
-# define Flying			(HFlying || EFlying)
+# define Flying			((HFlying || EFlying) && !BFlying)
 #endif
 	/* May touch surface; does not override any others */
 

src/cmd.c

@@ -1415,12 +1415,8 @@ int final;
 		you_are("levitating, at will", "");
 	    else
 		enl_msg(youtoo, are, were, "levitating", from_what(LEVITATION));
-	}
-	if (Flying) {
-	    if (Levitation)
-		you_can("also fly", from_what(FLYING));
-	    else
-		enl_msg(youtoo, are, were, "flying", from_what(FLYING));
+	} else if (Flying) {	/* can only fly when not levitating */
+	    enl_msg(youtoo, are, were, "flying", from_what(FLYING));
 	}
 	if (Underwater) {
 	    you_are("underwater", "");
@@ -1621,6 +1617,8 @@ attributes_enlightenment(mode, final)
 int mode;
 int final;
 {
+	static NEARDATA const char
+	    if_surroundings_permitted[] = " if surroundings permitted";
 	int ltmp, armpro;
 	char buf[BUFSZ];
 
@@ -1762,6 +1760,33 @@ int final;
 	if (Teleportation) you_can("teleport",from_what(TELEPORT));
 	if (Teleport_control)
 		you_have("teleport control",from_what(TELEPORT_CONTROL));
+	/* actively levitating handled earlier as a status condition */
+	if (BLevitation) {	/* levitation is blocked */
+	    long save_BLev = BLevitation;
+
+	    BLevitation = 0L;
+	    if (Levitation)
+		enl_msg(You_, "would levitate", "would have levitated",
+			if_surroundings_permitted, "");
+	    BLevitation = save_BLev;
+	}
+	/* actively flying handled earlier as a status condition */
+	if (BFlying) {		/* flight is blocked */
+	    long save_BFly = BFlying;
+
+	    BFlying = 0L;
+	    if (Flying) {
+		Sprintf(buf, "%s%s%s",
+			(save_BFly & I_SPECIAL) ?
+				" if you weren't levitating" : "",
+			((save_BFly & (FROMOUTSIDE|I_SPECIAL)) ==
+				(FROMOUTSIDE|I_SPECIAL)) ? " and" : "",
+			(save_BFly & FROMOUTSIDE) ?
+				if_surroundings_permitted : (const char *)"");
+		enl_msg(You_, "would fly", "would have flown", buf, "");
+	    }
+	    BFlying = save_BFly;
+	}
 	/* actively walking on water handled earlier as a status condition */
 	if (Wwalking && !walking_on_water())
 	    you_can("walk on water",from_what(WWALKING));

src/do_wear.c

@@ -190,7 +190,7 @@ Boots_on(VOID_ARGS)
 			incr_itimeout(&HFumbling, rnd(20));
 		break;
 	case LEVITATION_BOOTS:
-		if (!oldprop && !HLevitation) {
+		if (!oldprop && !HLevitation && !BLevitation) {
 			makeknown(uarmf->otyp);
 			float_up();
 			spoteffects(FALSE);
@@ -241,7 +241,8 @@ Boots_off(VOID_ARGS)
 			HFumbling = EFumbling = 0;
 		break;
 	case LEVITATION_BOOTS:
-		if (!oldprop && !HLevitation && !context.takeoff.cancelled_don) {
+		if (!oldprop && !HLevitation && !BLevitation &&
+		    !context.takeoff.cancelled_don) {
 			(void) float_down(0L, 0L);
 			makeknown(otyp);
 		}
@@ -875,7 +876,7 @@ register struct obj *obj;
 		}
 		break;
 	case RIN_LEVITATION:
-		if (!oldprop && !HLevitation) {
+		if (!oldprop && !HLevitation && !BLevitation) {
 		    float_up();
 		    learnring(obj, TRUE);
 		    spoteffects(FALSE);	/* for sinks */
@@ -987,8 +988,10 @@ boolean gone;
 		}
 		break;
 	case RIN_LEVITATION:
-		(void) float_down(0L, 0L);
-		if (!Levitation) learnring(obj, TRUE);
+		if (!BLevitation) {
+		    (void) float_down(0L, 0L);
+		    if (!Levitation) learnring(obj, TRUE);
+		}
 		break;
 	case RIN_GAIN_STRENGTH:
 		which = A_STR;

src/hack.c

@@ -14,6 +14,7 @@ STATIC_DCL void NDECL(dosinkfall);
 #endif
 STATIC_DCL boolean FDECL(findtravelpath, (BOOLEAN_P));
 STATIC_DCL boolean FDECL(trapmove, (int,int,struct trap *));
+STATIC_DCL void NDECL(switch_terrain);
 STATIC_DCL struct monst *FDECL(monstinroom, (struct permonst *,int));
 STATIC_DCL boolean FDECL(doorless_door, (int,int));
 STATIC_DCL void FDECL(move_update, (BOOLEAN_P));
@@ -1640,6 +1641,40 @@ invocation_message()
 	}
 }
 
+/* moving onto different terrain;
+   might be going into solid rock, inhibiting levitation or flight,
+   or coming back out of such, reinstating levitation/flying */
+STATIC_OVL void
+switch_terrain()
+{
+    struct rm *lev = &levl[u.ux][u.uy];
+    boolean blocklev = (IS_ROCK(lev->typ) || closed_door(u.ux, u.uy) ||
+			(Is_waterlevel(&u.uz) && lev->typ == WATER));
+
+    if (blocklev) {
+	/* called from spoteffects(), skip float_down() */
+	if (Levitation) You_cant("levitate in here.");
+	BLevitation |= FROMOUTSIDE;
+    } else if (BLevitation) {
+	BLevitation &= ~FROMOUTSIDE;
+	if (Levitation) float_up();
+    }
+    /* the same terrain that blocks levitation also blocks flight */
+    if (blocklev) {
+	if (Flying) You_cant("fly in here.");
+	BFlying |= FROMOUTSIDE;
+    } else if (BFlying) {
+	BFlying &= ~FROMOUTSIDE;
+	/* in case BFlying got set due to levitation which then went away
+	   while blocked; there'd be no float_down() with reset of BFlying */
+	if (!HLevitation && !ELevitation) BFlying &= ~I_SPECIAL;
+	/* [minor bug: we don't know whether this is beginning flight or
+	   resuming it; that could be tracked so that this message could
+	   be adjusted to "resume flying", but isn't worth the effort...] */
+	if (Flying) You("start flying.");
+    }
+}
+
 /* extracted from spoteffects; called by spoteffects to check for entering or
    leaving a pool of water/lava, and by moveloop to check for staying on one */
 boolean
@@ -1741,6 +1776,10 @@ boolean pick;
 	spotterrain = levl[u.ux][u.uy].typ;
 	spotloc.x = u.ux, spotloc.y = u.uy;
 
+	/* moving onto different terrain might cause Levitation to toggle */
+	if (spotterrain != levl[u.ux0][u.uy0].typ || !on_level(&u.uz, &u.uz0))
+	    switch_terrain();
+
 	if (pooleffects(TRUE)) goto spotdone;
 
 	check_special_room(FALSE);

src/polyself.c

@@ -88,6 +88,11 @@ set_uasmon()
 	PROPSET(PASSES_WALLS, passes_walls(mdat));
 	PROPSET(REGENERATION, regenerates(mdat));
 	PROPSET(REFLECTING, (mdat == &mons[PM_SILVER_DRAGON]));
+	/* levitation overrides flight */
+	if (HLevitation || ELevitation)
+	    BFlying |= I_SPECIAL;
+	else
+	    BFlying &= ~I_SPECIAL;
 
 #undef PROPSET
 

src/potion.c

@@ -904,33 +904,36 @@ peffects(otmp)
 	case POT_LEVITATION:
 	case SPE_LEVITATION:
 		if (otmp->cursed) HLevitation &= ~I_SPECIAL;
-		if(!Levitation) {
-			/* kludge to ensure proper operation of float_up() */
-			set_itimeout(&HLevitation, 1L);
-			float_up();
-			/* reverse kludge */
-			set_itimeout(&HLevitation, 0L);
-			if (otmp->cursed && !Is_waterlevel(&u.uz)) {
-	if((u.ux != xupstair || u.uy != yupstair)
-	   && (u.ux != sstairs.sx || u.uy != sstairs.sy || !sstairs.up)
-	   && (!xupladder || u.ux != xupladder || u.uy != yupladder)
-	) {
-					int dmg = uarmh ? 1 : rnd(10);
-					You("hit your %s on the %s.",
-						body_part(HEAD),
-						ceiling(u.ux,u.uy));
-					losehp(Maybe_Half_Phys(dmg),
-						"colliding with the ceiling",
-						KILLED_BY);
-				} else (void) doup();
+		if (!Levitation && !BLevitation) {
+		    /* kludge to ensure proper operation of float_up() */
+		    set_itimeout(&HLevitation, 1L);
+		    float_up();
+		    /* reverse kludge */
+		    set_itimeout(&HLevitation, 0L);
+		    if (otmp->cursed) {
+			if ((u.ux == xupstair && u.uy == yupstair) ||
+			    (sstairs.up && u.ux == sstairs.sx &&
+				    u.uy == sstairs.sy) ||
+			    (xupladder && u.ux == xupladder &&
+				    u.uy == yupladder)) {
+			    (void) doup();
+			} else if (has_ceiling(&u.uz)) {
+			    int dmg = uarmh ? 1 : rnd(10);
+
+			    You("hit your %s on the %s.",
+				body_part(HEAD), ceiling(u.ux,u.uy));
+			    losehp(Maybe_Half_Phys(dmg),
+				   "colliding with the ceiling", KILLED_BY);
 			}
+		    } /*cursed*/
 		} else
-			nothing++;
+		    nothing++;
 		if (otmp->blessed) {
 		    incr_itimeout(&HLevitation, rn1(50,250));
 		    HLevitation |= I_SPECIAL;
-		} else incr_itimeout(&HLevitation, rn1(140,10));
-		spoteffects(FALSE);	/* for sinks */
+		} else
+		    incr_itimeout(&HLevitation, rn1(140,10));
+		if (Levitation) spoteffects(FALSE);	/* for sinks */
 		break;
 	case POT_GAIN_ENERGY:			/* M. Stephenson */
 		{	register int num;

src/trap.c

@@ -2609,8 +2609,10 @@ float_up()
 				body_part(LEG));
 		}
 	}
+#if 0
 	else if(Is_waterlevel(&u.uz))
 		pline("It feels as though you've lost some weight.");
+#endif
 	else if(u.uinwater)
 		spoteffects(TRUE);
 	else if(u.uswallow)
@@ -2637,6 +2639,8 @@ float_up()
 	    }
 	}
 #endif
+	if (Flying) You("are no longer able to control your flight.");
+	BFlying |= I_SPECIAL;
 	return;
 }
 
@@ -2667,6 +2671,14 @@ long hmask, emask;     /* might cancel timeout */
 	ELevitation &= ~emask;
 	if(Levitation) return(0); /* maybe another ring/potion/boots */
 	nomul(0);	/* stop running or resting */
+	if (BFlying) {
+	    /* controlled flight no longer overridden by levitation */
+	    BFlying &= ~I_SPECIAL;
+	    if (Flying) {
+		You("have stopped levitating and are now flying.");
+		return 1;
+	    }
+	}
 	if(u.uswallow) {
 	    You("float down, but you are still %s.",
 		is_animal(u.ustuck->data) ? "swallowed" : "engulfed");