Re: chords as markups?

[address@hidden]

On 6 sept. 2012, at 09:49, Werner LEMBERG <address@hidden> wrote:

> 
>> After reading the CG stuff, If you feel any info should be brought
>> over to the users manual, post a patch and we can discuss it.  And,
>> of course, if after reading the CG stuff is still unclear on how
>> they work, lemme know.
> 
> OK, I've read it, and the concept of purity is explained well, thanks.
> However, it's still not clear to me why the example works.
> 
> . First of all, `make-XXX-stencil' seems to be completely
>   undocumented.  At least I can't find those functions in the
>   reference (except some unsystematic usage here and there).

I'm not sure who made them or when they made it into LilyPond, but you're 
certainly welcome to post a patch documenting them - I think it'd be helpful to 
have that documented.

> 
> . I would expect that both `make-circle-stencil' and
>   `make-filled-box-stencil' produce something which has a natural
>   height.

They do.  It's just that LilyPond doesn't know that they will because they're 
functions.  Whenever LilyPond doesn't know if a function will return a natural 
height, she assumes it won't.  This is why it needs to be wrapped in an 
unpure-pure container.  I'll revisit the CG and find a way to better explain 
this.

> Apparently, this isn't true.  Why?  This should be
>   mentioned, otherwise the example is not really comprehensible
>   IMHO.
> . Even if `make-XXX-stencil' produce objects with zero height, I
>   don't understand why the layout engine ignores it.  IMHO, zero
>   height is not the same as an empty stencil.

The layout engine ignores it because it is a function - LilyPond will simply 
ignore the function all together because there is no guarantee that it is pure 
(see above).

> 
> Maybe there is something else which I don't understand...
> 

I'll revisit the CG to find a better way to explain this - pester me if I 
forget.

Cheers,
MS

> 
> 
>  Werner