IMB tracer and targetting improvements.

IMB tracers now account for the possible explosion, so that the player
will get appropriate warnings and IMB-wielding monsters will consider
the affect that the spell could have on allies. Thus, this fixes
0005823.

There's also now a dedicated targetter for IMB, employing the same code
to determine what squares can be affected as the tracer, which has been
split out from the relevant section of the beam code.

Finally, on account of the above split, the IMB explosion code itself is
now a bit cleaner.

1 files changed, 2 insertions, 0 deletions

diff --git a/crawl-ref/source/beam.h b/crawl-ref/source/beam.h
index 36cd8e88dc..9941ca255a 100644
--- a/crawl-ref/source/beam.h
+++ b/crawl-ref/source/beam.h
@@ -329,6 +329,8 @@ bool napalm_monster(monster* mons, const actor* who, int levels = 1,
                     bool verbose = true);
 void fire_tracer(const monster* mons, struct bolt &pbolt,
                   bool explode_only = false);
+bool imb_can_splash(coord_def origin, coord_def center,
+                    std::vector<coord_def> path_taken, coord_def target);
 spret_type zapping(zap_type ztype, int power, bolt &pbolt,
                    bool needs_tracer = false, const char* msg = NULL,
                    bool fail = false);