Move ambitus print callback to scheme.

Move ambitus print callback to scheme.

* implement ambitus::print callback in output-lib.scm

* add interface description to define-grob-interfaces.scm

* allow user override of padding using grob property 'gap

* move 'join-heads to user properties

* remove ambitus.cc/.hh

* tidy ambitus-engraver.cc

* add regression test for 'gap

* add convert rule for ly:ambitus::print

[hanwenn, 2009-08-20 03:12:26]

Nice to see this type of code migrate to Scheme.

http://codereview.appspot.com/110047/diff/1/11
File scm/output-lib.scm (right):

http://codereview.appspot.com/110047/diff/1/11#newcode778
Line 778: (ly:grob-suicide! grob)
this does not make sense. did you forget to check the length of the noteheads
array? - why would someone not set join-heads?

http://codereview.appspot.com/110047/diff/1/11#newcode782
Line 782: (head-up (ly:grob-array-ref heads 1))
you need to check the length of the array

http://codereview.appspot.com/110047/diff/1/11#newcode795
Line 795: (x-ext (cons (/ (- width) 2) (/ width 2)))
this looks like a nice candidate for a small function 

  (symmetric-interval (/ width 2))

http://codereview.appspot.com/110047/diff/1/11#newcode801
Line 801: (ly:grob-suicide! grob))))))
it would be nice to explicitly return something, eg '() in the suicide case -
with all the nesting it is hard to tell what the final result is.

[Neil Puttock, 2009-08-21 00:35:42]

On 2009/08/20 03:12:26, hanwenn wrote:

> http://codereview.appspot.com/110047/diff/1/11
> File scm/output-lib.scm (right):
> 
> http://codereview.appspot.com/110047/diff/1/11#newcode778
> Line 778: (ly:grob-suicide! grob)
> this does not make sense. did you forget to check the length of the noteheads
> array? - why would someone not set join-heads?

I don't know; I just copied it from the C++ code.  Since it's possible to hide
the line using 'transparent or 'stencil, I guess it's pretty much redundant
anyway.

> 
> http://codereview.appspot.com/110047/diff/1/11#newcode782
> Line 782: (head-up (ly:grob-array-ref heads 1))
> you need to check the length of the array

I thought this would be unnecessary, since the array must have two elements
ordered by pitch if the pitch interval isn't empty; otherwise the engraver
suicides the AmbitusLine.

Of course, if you prefer, I'll add a check using ly:grob-array-length.

> 
> http://codereview.appspot.com/110047/diff/1/11#newcode795
> Line 795: (x-ext (cons (/ (- width) 2) (/ width 2)))
> this looks like a nice candidate for a small function 
> 
>   (symmetric-interval (/ width 2))

OK.

> 
> http://codereview.appspot.com/110047/diff/1/11#newcode801
> Line 801: (ly:grob-suicide! grob))))))
> it would be nice to explicitly return something, eg '() in the suicide case -
> with all the nesting it is hard to tell what the final result is.

OK.

Thanks,
Neil

[hanwenn, 2009-08-26 15:13:50]

LGTM

I still indentation diffs though.