Re: Better pure height approximations for beamed rests. (issue 4860043)

[Keith OHara]

On Fri, 27 Apr 2012 03:02:51 -0700, address@hidden <address@hidden> wrote:

> On 27 avr. 2012, at 09:45, Keith OHara wrote:
>
> > On Thu, 26 Apr 2012 23:44:24 -0700, <address@hidden> wrote:
> >
> > > lily/beam.cc:1743: Beam::pure_rest_collision_callback (SCM smob, SCM
> > > prev_offset,
> > >
> > > You're right - this is an error.  Do you want me to fix it or are you
> > > working on a patch into which the fix could be incorporated?
> >
> > I am re-ordering the arguments in that one C function, but I don't read Scheme 
> > so I am not sure if the observed order of the data is the intended order, or 
> > the conventional order.
> >
> > Your addition to the docs is pretty explicit that 'start' and 'end' are always 
> > the last two arguments, even in a chained-offset-callback where there are extra 
> > arguments.  On the other hand, call-pure-function seems to put 'start' and 
> > 'end' in slots 2 and 3, with any other arguments attached later.
>
>
> Call pure function puts start and end in the final two slots.  The optional 
> arguments are passed in in slot two as a variable called `args' (check out 
> lily/grob-property.cc and scm/define-grobs.scm).

I did check them out; that's how I know I don't read Scheme.

 326 SCM
 327 call_pure_function (SCM unpure, SCM args, int start, int end)
 328 {
 329   SCM scm_call_pure_function = ly_lily_module_constant 
("call-pure-function");
 330
 331   return scm_apply_0 (scm_call_pure_function,
 332                       scm_list_4 (unpure, args, scm_from_int (start), 
scm_from_int (end)));
 333 }
 334

2749 (define-public (call-pure-function unpure args start end)
2750   (if (ly:unpure-pure-container? unpure)
           (...) ;; the true branch
2760       (if (ly:simple-closure? unpure)
2761           (ly:eval-simple-closure (car args) unpure start end)
2762           (if (not (procedure? unpure))
2763               unpure
2764               (if (memq unpure pure-functions)
2765                   (apply unpure args)
2766                   (let ((pure (assq unpure pure-conversions-alist)))
2767                     (if pure
2768                         (apply (cdr pure)
2769                                (append
2770                                 (list (car args) start end)
2771                                 (cdr args))))))))))

I think this assembles
 (,pure-chain-offset-callback (car args) start end (cdr args))

it seems the address register would hold the Grob* and the decrement register a 
lists of remaining arguments (prev_offset in my case).