Re: Bug in Lookup::bezier_sandwich

[address@hidden]

Sent from my iPhone

> On 30 août 2014, at 18:54, "Jürgen 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:
>   http://lilypond.org/doc/v2.14/Documentation/a9/lily-551aed0c.png
>   or (with more context) here:
>   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:
>   http://lilypond.org/doc/v2.15/Documentation/bf/lily-ac979051.png
>   or (with more context) here:
>   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 be
>   great!
> 
>   Thanks a lot,
>   Juergen
> _______________________________________________
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I can have a look at it this week - thanks for pointing it out!

~Mike