Adjust corona's interaction with invisibility

Since one of corona's main benefits is being able to make invisible
things visible, it is rather odd that they can simply cast invisibility
again to dispel the corona. Now corona acts similarly to other backlight
effects (like sticky flame), making invisible things visible for as long
as it lasts. This commit also removes an odd special-casing that made
corona's duration against invisible things extremely brief and prevented
extending with upon recast.

Finally, this also gives more informative messages in some cases where
the player casts invisibility, but does not turn invisible due to being
backlit (this was only handled for magic contamination and not sticky
flame, and now is handled for both of these and corona additionally)

1 files changed, 0 insertions, 12 deletions

diff --git a/crawl-ref/source/spl-monench.cc b/crawl-ref/source/spl-monench.cc
index ef809fc11f..4954deb590 100644
--- a/crawl-ref/source/spl-monench.cc
+++ b/crawl-ref/source/spl-monench.cc
@@ -89,18 +89,6 @@ bool backlight_monsters(coord_def where, int pow, int garbage)
     mon_enchant zin_bklt = mons->get_ench(ENCH_SILVER_CORONA);
     const int lvl = bklt.degree + zin_bklt.degree;
 
-    // This enchantment overrides invisibility (neat).
-    if (mons->has_ench(ENCH_INVIS))
-    {
-        if (!mons->has_ench(ENCH_CORONA) && !mons->has_ench(ENCH_SILVER_CORONA))
-        {
-            mons->add_ench(
-                mon_enchant(ENCH_CORONA, 1, 0, random_range(30, 50)));
-            simple_monster_message(mons, " is lined in light.");
-        }
-        return true;
-    }
-
     mons->add_ench(mon_enchant(ENCH_CORONA, 1));
 
     if (lvl == 0)