Re: Add Scheme function to return column associated with Item. (issue 203910043 by address@hidden)

[Thomas Morley]

2015-02-15 19:28 GMT+01:00 Thomas Morley <address@hidden>:
> 2015-02-15 18:50 GMT+01:00 David Nalesnik <address@hidden>:
>> On Sun, Feb 15, 2015 at 7:58 AM, Urs Liska <address@hidden> wrote:
>>
>>> Can't judge the code but the idea looks great :-)
>>>
>>>
>> Thanks--I'm noticing that bits of code get reused on the lists, so there's
>> a need.   This will help tuck away some of the code gobbledygook that is so
>> off-putting..
>>
>> It occurs to me that it shouldn't be any trouble to add something like
>> ly:item-location later on.  It could return (global-timestep . (measure .
>> measure-position))..
>>
>> David
>
>
>
> Hi David,
>
> I can't review C++ code, though it looks like the C++-version of your:
>
> #(define (get-paper-column grob)
>    (if (not (ly:grob? grob))
>        (ly:message "column not found")
>        (if (grob::has-interface grob 'paper-column-interface)
>            grob
>            (get-paper-column (ly:grob-parent grob X)))))
>
> Some time ago I wrote a more generic code:

Oops, definition for 'grob-name' is missing:

#(define grob-name
  (lambda (x)
    (if (ly:grob? x)
        (assq-ref (ly:grob-property x 'meta) 'name)
        (ly:error "~a is not a grob" x))))
>
> #(define (look-up-for-parent name-symbol axis grob)
> "
>  Return the parent of @var{grob}, specified by it's @var{name-symbol} in
>  axis @var{axis}.
>  If not found, look up for the next parent.
> "
>  (let* ((parent (ly:grob-parent grob axis)))
>  (cond
>    ((not (ly:grob? parent))
>     (ly:error
>        (_"Perhaps typing error for \"~a\" or \"~a\" is not in the 
> parent-tree.")
>        name-symbol name-symbol))
>    ((not (equal? name-symbol (grob-name parent)))
>     (look-up-for-parent name-symbol axis parent))
>    (else parent))))
>
>
> I wonder whether something like this may be implemented at C++ level
> and your "ly:item-get-column" as a special case of it.
>
> What do you think?
>
>
> Cheers,
>   Harm