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List:       lilypond-devel
Subject:    Re: empty-stencil and point-stencil
From:       "Trevor Daniels" <t.daniels () treda ! co ! uk>
Date:       2009-06-26 6:43:24
Message-ID: 050E681EDD5C40D1AC4AF48F50B0AEC3 () TrevorLaptop
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Trevor Daniels wrote Friday, June 26, 2009 7:32 AM


>
> Carl D. Sorensen wrote Wednesday, June 17, 2009 9:21 AM
>
>>On 6/16/09 1:51 PM, "Mark Polesky" <markpolesky@yahoo.com> wrote:
>>>
>>> Trevor, could you add a bit to your recent LM 4.3.1 patch about
>>> empty-stencil and point-stencil? They are suitable substitutes 
>>> for
>>> #'stencil = ##f.
>>>
>>> \override <grob> #'stencil = #empty-stencil
>>> \override <grob> #'stencil = #point-stencil
>>>
>>> See
>>> http://lists.gnu.org/archive/html/lilypond-devel/2009-06/msg00332.html
>>> for a very recent discussion. I actually don't fully understand
>>> the subtleties of discerning when one is more appropriate than
>>> the other, but it sounds like you might!
>>
>> I don't understand why empty-stencil has a non-zero extent; that 
>> means it
>> takes up space.

I should have added this to my earlier mail, and I also
forgot to cc the list (well, it is early):

empty-stencil is defined in define-markup-commands.scm as:

(define-public empty-stencil (ly:make-stencil '() '(1 . -1) '(1 
. -1)))

Normally a left extent of 1 would be truncated to 0 and
a right extent of -1 to 0, but this doesn't seem to
happen.  I don't understand why.  Its effect is not as
expected, at least not when used on NoteHead, which is
why I used point-stencil.

>> I believe that point-stencil should be used to replace ##f, 
>> because we want
>> to take up no space, and point-stencil has zero extent.
>
> Yes; I used point-stencil in the example when I changed LM 4.3.1.
>
> Trevor 




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