[Lilypond-auto] Issue 4087 in lilypond: Bug in Lookup::bezier_sandwich

[lilypond]

Status: Accepted
Owner: address@hidden
Labels: Type-Defect

New issue 4087 by address@hidden: Bug in Lookup::bezier_sandwich
https://code.google.com/p/lilypond/issues/detail?id=4087

 > On 30 aout 2014, at 18:54, "Juergen Reuter" <address@hidden>
   wrote:
   >
   >   Hi all,
   >   there is a bug in Lookup::bezier_sandwich that severely affects
   ancient
   >   notation.  This method was originally added to lookup.cc for
   >   flexa/porrectus support.
   >
   >   In version 2.14, the bezier_sandwich curve still looks correctly,
   see
   >   here:
   >   [3]http://lilypond.org/doc/v2.14/Documentation/a9/lily-551aed0c.png
   >   or (with more context) here:
   >   [4]http://lilypond.org/doc/v2.14/Documentation/notation/
   ancient-notation
   >
   >   In version 2.15 and later, the bezier_sandwich curve has zero
   height at
   >   its right end, which is bad; see here:
   >   [5]http://lilypond.org/doc/v2.15/Documentation/bf/lily-ac979051.png
   >   or (with more context) here:
   >   [6]http://lilypond.org/doc/v2.15/Documentation/notation/
   ancient-notation
   >
   >   I tried to track down the problem and found the following
   suspicious
   >   commit:
   >
   >   commit 35725a573e47be7c02c51964641ea534fb88be6b
   >   Author: Mike Solomon <address@hidden>
   >   Date:   Mon Feb 6 15:03:20 2012 +0100
   >       Gets rid of bezier-sandwich stencil
   >   diff --git a/lily/lookup.cc b/lily/lookup.cc
   >   index 3f393e0..7b63b83 100644
   >   --- a/lily/lookup.cc
   >   +++ b/lily/lookup.cc
   >   @@ -449,22 +449,32 @@ Lookup::slur (Bezier curve, Real curvethick,
   Real
   >   linethick,
   >    Stencil
   >    Lookup::bezier_sandwich (Bezier top_curve, Bezier bottom_curve,
   Real
   >   thickness)
   >    {
   >   -  /*
   >   -    Need the weird order b.o. the way PS want its arguments
   >   -  */
   >   -  SCM list = SCM_EOL;
   >   -  list = scm_cons (ly_offset2scm (bottom_curve.control_[3]),
   list);
   >   -  list = scm_cons (ly_offset2scm (bottom_curve.control_[0]),
   list);
   >   -  list = scm_cons (ly_offset2scm (bottom_curve.control_[1]),
   list);
   >   -  list = scm_cons (ly_offset2scm (bottom_curve.control_[2]),
   list);
   >   -  list = scm_cons (ly_offset2scm (top_curve.control_[0]), list);
   >   -  list = scm_cons (ly_offset2scm (top_curve.control_[3]), list);
   >   -  list = scm_cons (ly_offset2scm (top_curve.control_[2]), list);
   >   -  list = scm_cons (ly_offset2scm (top_curve.control_[1]), list);
   >   -
   >   -  SCM horizontal_bend = scm_list_n (ly_symbol2scm
   ("bezier-sandwich"),
   >   -                                    ly_quote_scm (list),
   >   +  SCM commands  = scm_list_n (ly_symbol2scm ("moveto"),
   >   +                              scm_from_double
   >   (top_curve.control_[0][X_AXIS]),
   >   +                              scm_from_double
   >   (top_curve.control_[0][Y_AXIS]),
   >   +                              ly_symbol2scm ("curveto"),
   >   +                              scm_from_double
   >   (top_curve.control_[1][X_AXIS]),
   >   +                              scm_from_double
   >   (top_curve.control_[1][Y_AXIS]),
   >   +                              scm_from_double
   >   (top_curve.control_[2][X_AXIS]),
   >   +                              scm_from_double
   >   (top_curve.control_[2][Y_AXIS]),
   >   +                              scm_from_double
   >   (top_curve.control_[3][X_AXIS]),
   >   +                              scm_from_double
   >   (top_curve.control_[3][Y_AXIS]),
   >   +                              ly_symbol2scm ("curveto"),
   >   +                              scm_from_double
   >   (bottom_curve.control_[2][X_AXIS]),
   >   +                              scm_from_double
   >   (bottom_curve.control_[2][Y_AXIS]),
   >   +                              scm_from_double
   >   (bottom_curve.control_[1][X_AXIS]),
   >   +                              scm_from_double
   >   (bottom_curve.control_[1][Y_AXIS]),
   >   +                              scm_from_double
   >   (bottom_curve.control_[0][X_AXIS]),
   >   +                              scm_from_double
   >   (bottom_curve.control_[0][Y_AXIS]),
   >   +                              ly_symbol2scm ("closepath"),
   >   +                              SCM_UNDEFINED);
   >   +
   >   +  SCM horizontal_bend = scm_list_n (ly_symbol2scm ("path"),
   >   scm_from_double (thickness),
   >   +                                    ly_quote_scm (commands),
   >   +                                    ly_quote_scm (ly_symbol2scm
   >   ("round")),
   >   +                                    ly_quote_scm (ly_symbol2scm
   >   ("round")),
   >   +                                    SCM_BOOL_T, SCM_UNDEFINED);
   >
   >      Interval x_extent = top_curve.extent (X_AXIS);
   >
   >   I do not fully understand the rationale / implications of this
   change,
   >   so I do really know what to do here without affecting other places
   in
   >   the code.  By the way, ancient notation does not make use of the
   >   "thickness" argument; probably it has been introduced for some
   other
   >   use elsewhere.
   >
   >   Could someone of the active developers look into this?  That would

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