Make blocked beams fall back to visible paths if possible (#8804).

In this position, you would be able to see the kobold, but trying to
shoot it would say your line of fire is blocked by the wall:

  ..#@
  K.8.

If the statue weren't there the beam would avoid the wall perfectly
well.  Furthermore, the "Aim" prompt does in fact say "fire blocked by a
granite statue", not "wall"; only the tracer and beam reported the
opaque wall as the reason for losing LOF.

When no LOS_SOLID_SEE ray is found for a beam, now we first try falling
back to a LOS_DEFAULT ray; only if that too fails do we take the
straight-path fallback.

1 files changed, 6 insertions, 3 deletions

diff --git a/crawl-ref/source/beam.cc b/crawl-ref/source/beam.cc
index 7c8f74ca76..7f4e84f8f7 100644
--- a/crawl-ref/source/beam.cc
+++ b/crawl-ref/source/beam.cc
@@ -681,10 +681,13 @@ void bolt::apply_beam_conducts()
 
 void bolt::choose_ray()
 {
-    if (!chose_ray || reflections > 0)
+    if ((!chose_ray || reflections > 0)
+        && !find_ray(source, target, ray, opc_solid_see)
+        // If fire is blocked, at least try a visible path so the
+        // error message is better.
+        && !find_ray(source, target, ray, opc_default))
     {
-        if (!find_ray(source, target, ray, opc_solid_see))
-            fallback_ray(source, target, ray);
+        fallback_ray(source, target, ray);
     }
 }