Add \path markup command, and use it for \eyeglasses. (issue1730044)

[Carl . D . Sorensen]

Thanks for doing this.  I think this looks quite good.

As I mention below, I think it might be best to eliminate the "style"
arguments and make them part of the properties.  We already have
'thickness as a property, and we could add 'path-details.

Or we could make 'path-thickness part of 'path-details, and the all the
things needed to control the path would be part of 'path-details.

Thanks,

Carl



http://codereview.appspot.com/1730044/diff/1/2
File scm/define-markup-commands.scm (right):

http://codereview.appspot.com/1730044/diff/1/2#newcode622
scm/define-markup-commands.scm:622: (number? number? number? boolean?
string?)
Can (and/or should) cap, join, and fill become part of a path-details
property?

It's convenient when creating a new markup type to put all the arguments
needed into an argument list.  But it's more consistent with LilyPond
syntax to have all the things that affect appearance be properties that
can have default values set (and documented) in the code.

http://codereview.appspot.com/1730044/diff/1/2#newcode668
scm/define-markup-commands.scm:668: \"
I think this inline snippet is fine.  What characteristics of the
snippet need to be "better" in your opinion?

http://codereview.appspot.com/1730044/diff/1/2#newcode684
scm/define-markup-commands.scm:684: (cons 0 0)))
Is it possible to have the path command estimate reasonable extents,
rather
than using (0 . 0) and (0 . 0)?  Since we know the thickness of the
line, and
we have a list of points, it seems we should be able to keep track of
the
maximum and minimum X and Y coordinates during the path creation.

http://codereview.appspot.com/1730044/show