Creates callback for stem-begin-position.

Creates callback for stem-begin-position.

[MikeSol, 2011-07-16 16:34:05]

On Jul 1, 2011, at 5:50 PM, Han-Wen Nienhuys wrote: 
>
>On Thu, Jun 30, 2011 at 12:46 PM, mike@apollinemike.com
><mike@apollinemike.com> wrote:                        
>can you show png examples of what you're trying to do?
>
>Honestly, I cannot allow this patch in its current design. I don't see
>a reason for an obscure feature to be touching code of note-spacing,
>stem-tremolo, stem, beam etc.                                        
>
>If we add patches like this for every composer's favorite avant-garde
>notation, the large parts of the lilypond codebase will shortly become
>a tangle of hard to understand dependencies; code for uncommon
>notation constructs should only be added if their implementation is 
>separate, modular and generic. This patch is neither.                
>
>Can you try a minimal implementation first? For example,     
>
>* Have a stem property that determines the end of the stem.
> Currently, we have
>
>   y2 = Staff_symbol_referencer::get_position (lh); 

Done in this patch.

Cheers,
MS

[hanwenn, 2011-07-18 00:53:01]

LGTM

There is some code that adjusts for the shape of the notehead as well (look for
calls to 
Note_head::stem_attachment_coordinate). Can you have a look if you can work that
into your code too?

[MikeSol, 2011-07-18 17:44:26]

On 2011/07/18 00:53:01, hanwenn wrote:
> LGTM
> 
> There is some code that adjusts for the shape of the notehead as well (look
for
> calls to 
> Note_head::stem_attachment_coordinate). Can you have a look if you can work
that
> into your code too?

Done.  New patch set uploaded.

[Janek Warchol, 2011-07-18 18:38:21]

My "review" will be a bit non-standard (as i'm still a rookie programmer): i
understand what's going on here, so it's probably good :)

[hanwenn, 2011-07-19 12:36:57]

LGTM

please push after regtests come out clean

http://codereview.appspot.com/4752048/diff/4001/lily/stem.cc
File lily/stem.cc (right):

http://codereview.appspot.com/4752048/diff/4001/lily/stem.cc#newcode754
lily/stem.cc:754: */
this comment looks outdated. I think the work of ledger is done in
Note_head::stem_attach_coord() nowadays.