Re: stencil.scm: add make-path-stencil function (issue 54050043)

[paulwmorris]

Reviewers: ,

Message:
This patch introduces a make-path-stencil function that offers the
benefits of the current make-connected-path-stencil function without its
limitations:

- Like make-connected-path-stencil it automatically calculates the
stencil extents so you don't have to do it manually (no small task when
the extents are somewhere on a curve).

- Allows use of all path commands, both relative and absolute, not just
lineto and curveto.  (i.e. lineto rlineto curveto rcurveto moveto
rmoveto closepath)  This allows "unconnected" paths with multiple
segments. (i.e. allows (r)moveto in the middle of the path expression)

- Allows optional use of single letter syntax used in standard SVG path
commands: L, l, C, c, M, m, Z, z.  This is useful for those familiar
with the SVG syntax, and makes it convenient to take path code from SVG
files and insert it into LilyPond files.  (see
https://developer.mozilla.org/en-US/docs/Web/SVG/Tutorial/Paths)

make-connected-path-stencil is still available for use and/or backwards
compatibility, but refactored so that it calls make-path-stencil after
syntax conversion.  Here are some examples to show the syntax:

\version "2.18.0"
{

  c'1^\markup \stencil
  #(make-path-stencil
    `(rmoveto 0 0
       rlineto 2 0
       rlineto 0 -2
       rlineto -2 0
       closepath
       rmoveto 1.1 -1.1
       rlineto 2 0
       rlineto 0 -2
       rlineto -2 0
       closepath
       rmoveto 1.1 -1.1
       rlineto 2 0
       rlineto 0 -2
       rlineto -2 0
       closepath)
    0.2 1 1 #f)

  c'1^\markup \stencil
  #(make-path-stencil
    '(m -1 1
       c 0 0.75 1 0.75 1 0
       c 0 -0.75 -1 -0.75 -1 0
       c -1 0 -1 1.5 -0.5 1.5
       m 0.5 -1.5
       c -1 0 -1 -1.5 -0.5 -1.5
       m 1.5 1.5
       c 2.5 0 2.5 4 4 4
       m -4 -4
       c 2.5 0 2.5 -4 4 -4)
    0.2 1 1 #f)
}

Here are snippets demonstrating each of the current ways to make a path
stencil:
http://lsr.dsi.unimi.it/LSR/Item?id=891
http://lsr.dsi.unimi.it/LSR/Item?id=623

Thanks for reviewing.

Description:
stencil.scm: add make-path-stencil function

supports all path commands both relative and absolute:
lineto, rlineto, curveto, rcurveto, moveto, rmoveto, closepath
also supports single letter syntax used in standard SVG path commands:
L, l, C, c, M, m, Z, z.
Refactors make-connected-path-stencil for backwards compatibility and
continued use

Please review this at https://codereview.appspot.com/54050043/

Affected files (+104, -44 lines):
  M scm/stencil.scm