Re: Anybody invested in ly:make-simple-closure?

[David Kastrup]

Han-Wen Nienhuys <address@hidden> writes:

> IIRC, it was introduced to compose offset callbacks,

Oh, it's still being used for that as far as I can tell.  Just not from
Scheme.

> but a quick check doesn't reveal any historical uses.

The last Scheme use of chain-grob-member-functions was likely removed
with

commit 1d9a73b13ee576d28c0f41f5b243f2ebb1ff9fcf
Author: Mike Solomon <address@hidden>
Date:   Fri Oct 21 09:03:43 2011 +0200

    Implements consistent beam slopes across line breaks.
    
    This is a mostly an internal reorganization of the beam code that
    has several concrete impacts on the way beam slopes are calculated:
    
    * ly:beam::calc-least-squares-positions, ly:beam::calc-slope-damping,
      and ly:beam::shift-region-to-valid are now all instance methods of
      Beam_scoring_problem and thus no longer open to the users.
    * by being internal methods, these functions all use the same information
      (x positions of stems, stem infos, etc.) stored in private variables.
    * this sharing of information allows for broken beams to share information
      between their parts, which leads to the consistent slope calculation
    
    Additionally, ly:beam::quanting, which used to take the arguments of
    a grob and a pair of positions, now only takes the grob, as it is
    the sole generator of positions.  All of the functions in layout-beam.scm
    that relied on multiple Scheme callbacks being chained now only use this
    function.
    
    To turn on this feature, use \override Beam #'consistent-slope = ##t.

and one extract of the diff would be

diff --git a/scm/define-grobs.scm b/scm/define-grobs.scm
index 05ba013..acea431 100644
--- a/scm/define-grobs.scm
+++ b/scm/define-grobs.scm
@@ -383,15 +383,7 @@
 
        (gap . 0.8)
        (neutral-direction . ,DOWN)
-       (positions .  ,(ly:make-simple-closure
-                       (ly:make-simple-closure
-                        (list chain-grob-member-functions
-                          `(,cons 0 0)
-                          ly:beam::calc-least-squares-positions
-                          ly:beam::slope-damping
-                          ly:beam::shift-region-to-valid
-                          ly:beam::quanting
-                          ))))
+       (positions . ,ly:beam::quanting)

And I am quite happy that I don't need to replace that code myself any
more.

-- 
David Kastrup