refine blocked levitation/flight (trunk only)

     Levitation side-effects get skipped if Levitation toggles while it
is blocked, so BFlying (the reason Flying is blocked) could become stale
in some situations.  Enlightment feedback about latent flight capability
was the only thing affected.

include/extern.h

@@ -1750,6 +1750,7 @@ E void NDECL(self_invis_message);
 /* ### polyself.c ### */
 
 E void NDECL(set_uasmon);
+E void NDECL(float_vs_flight);
 E void NDECL(change_sex);
 E void FDECL(polyself, (int));
 E int FDECL(polymon, (int));

src/cmd.c

@@ -1775,16 +1775,13 @@ int final;
 	    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, "");
-	    }
+	    if (Flying)
+		enl_msg(You_, "would fly", "would have flown",
+			Levitation ? "if you weren't levitating" :
+			  (save_BFly == FROMOUTSIDE) ?
+			    if_surroundings_permitted :
+			    /* both surroundings and [latent] levitation */
+			    " if circumstances permitted", "");
 	    BFlying = save_BFly;
 	}
 	/* actively walking on water handled earlier as a status condition */

src/do_wear.c

@@ -194,6 +194,8 @@ Boots_on(VOID_ARGS)
 			makeknown(uarmf->otyp);
 			float_up();
 			spoteffects(FALSE);
+		} else {
+		    float_vs_flight(); /* maybe toggle (BFlying & I_SPECIAL) */
 		}
 		break;
 	default: impossible(unknown_type, c_boots, uarmf->otyp);
@@ -245,6 +247,8 @@ Boots_off(VOID_ARGS)
 		    !context.takeoff.cancelled_don) {
 			(void) float_down(0L, 0L);
 			makeknown(otyp);
+		} else {
+		    float_vs_flight(); /* maybe toggle (BFlying & I_SPECIAL) */
 		}
 		break;
 	case LOW_BOOTS:
@@ -880,6 +884,8 @@ register struct obj *obj;
 		    float_up();
 		    learnring(obj, TRUE);
 		    spoteffects(FALSE);	/* for sinks */
+		} else {
+		    float_vs_flight(); /* maybe toggle (BFlying & I_SPECIAL) */
 		}
 		break;
 	case RIN_GAIN_STRENGTH:
@@ -991,6 +997,8 @@ boolean gone;
 		if (!BLevitation) {
 		    (void) float_down(0L, 0L);
 		    if (!Levitation) learnring(obj, TRUE);
+		} else {
+		    float_vs_flight(); /* maybe toggle (BFlying & I_SPECIAL) */
 		}
 		break;
 	case RIN_GAIN_STRENGTH:

src/hack.c

@@ -543,6 +543,9 @@ dosinkfall()
 	    off_msg(obj);
 	}
 	HLevitation--;
+	/* probably moot; we're either still levitating or went
+	   through float_down(), but make sure BFlying is up to date */
+	float_vs_flight();
 }
 #endif
 
@@ -1665,9 +1668,7 @@ switch_terrain()
 	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;
+	float_vs_flight();	/* maybe toggle (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...] */

src/polyself.c

@@ -88,11 +88,8 @@ 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;
+
+	float_vs_flight(); /* maybe toggle (BFlying & I_SPECIAL) */
 
 #undef PROPSET
 
@@ -101,6 +98,18 @@ set_uasmon()
 #endif
 }
 
+/* Levitation overrides Flying; set or clear BFlying|I_SPECIAL */
+void
+float_vs_flight()
+{
+	/* floating overrides flight; normally float_up() and float_down()
+	   handle this, but sometimes they're skipped */
+	if (HLevitation || ELevitation)
+	    BFlying |= I_SPECIAL;
+	else
+	    BFlying &= ~I_SPECIAL;
+}
+
 /* for changing into form that's immune to strangulation */
 STATIC_OVL void
 check_strangling(on)

src/potion.c

@@ -934,6 +934,7 @@ peffects(otmp)
 		} else
 		    incr_itimeout(&HLevitation, rn1(140,10));
 		if (Levitation) spoteffects(FALSE);	/* for sinks */
+		float_vs_flight();
 		break;
 	case POT_GAIN_ENERGY:			/* M. Stephenson */
 		{	register int num;