Re: beam.cc:pure-rest-collision-callback Place on staff lines; issue 2468 (issue 6035053)

[k-ohara5a5a]

Reviewers: Graham Percival, dak,

Message:
On 2012/04/15 15:32:10, dak wrote:

> if max/min trigger, rint is applied to some rest_max_pos.  It would >
appear that it should rather apply only to the calculated mean.

I want the final output to be an integral number of staff spaces, and
rest_max_pos might not be.  (Despite its name, rest_max_pos is in units
of staff-spaces, usually 2.5)

> every second staff line will get avoided for values in between.

Yes, the tentative placement for beamed rests favors the middle,
uppermost, and lowermost lines, in the usual five-line staff.

An improvement would be to round-to-larger, as in
rest_collision_callback() when it sets the final position of the rest.
That function is also more careful to make the shift relative to
'prev_offset' an integral number of staff spaces, rather than the
position relative to staff-center.

Description:
beam.cc:pure-rest-collision-callback Place on staff lines; issue 2468

Please review this at http://codereview.appspot.com/6035053/

Affected files:
  M lily/beam.cc


Index: lily/beam.cc
diff --git a/lily/beam.cc b/lily/beam.cc
index  
0cfc3e193cba6b3feea911abb09a6f9e5118d6c2..0cb9946eec038e9fca0960072a0fa5d49e712a7c  
100644
--- a/lily/beam.cc
+++ b/lily/beam.cc
@@ -1372,7 +1372,7 @@ Beam::pure_rest_collision_callback (SCM smob,
     then bound it by the minimum and maximum positions outside the staff.
     4.0 = 2.0 to get out of staff space * 2.0 for the average
   */
-  amount = min (max ((Stem::head_positions (left)[beamdir] +  
Stem::head_positions (right)[beamdir]) / 4.0, rest_max_pos[DOWN]),  
rest_max_pos[UP]);
+  amount = rint( min (max ((Stem::head_positions (left)[beamdir] +  
Stem::head_positions (right)[beamdir]) / 4.0, rest_max_pos[DOWN]),  
rest_max_pos[UP]));

   return scm_from_double (amount);
 }