Re: polyphonic shorthand; line-spanner-interface in Hairpin

[Carl D. Sorensen]

Thanks, Joe.

I think this may be what Kieren needs.

I'm pretty sure he wants to just adjust the length of the hairpin without
adjusting the spacing.

Carl


On 3/17/09 6:40 PM, "Joe Neeman" <address@hidden> wrote:

> On Tue, 2009-03-17 at 16:47 -0600, Carl D. Sorensen wrote:
>> 
>> 
>> On 3/17/09 3:48 PM, "Kieren MacMillan" <address@hidden>
>> wrote:
>> 
>>> Hi Carl,
>>> 
>>>> One issue that comes up in your proposal is that a 1/16 note column
>>>> does not
>>>> take up 1/16 of a whole note column.  So exactly what space are you
>>>> thinking
>>>> you want?
>>> 
>>> In the perfect scenario, I suppose Lilypond would "Do The Right Thing":
>>>     1. If there were another music event at the moment the Hairpin
>>> was set to begin (delayed) or end (trimmed), it would line up as
>>> expected.
>> 
>> So how about this as an explanation of DTRT?
>> 
>> Let's assume that the hairpin is a spanner (this much is correct, I think)
>> and that we know the musical length of the span (This is known because we
>> have the musical moment of the start and the musical moment of the end of
>> the hairpin.)
>> 
>> Then we define the delayed start moment as the start moment of the hairpin
>> plus the specified delay.
>> 
>> We define the trimmed end moment as the end moment of the hairpin minus the
>> specified trim amount.
>> 
>> Now I'm getting very iffy.   If there's a musical paper column at the
>> delayed start moment and the trimmed end moment, then we would want to shift
>> the spanner to those musical paper columns.
>> 
>> If not, then we have to adjust the size of the hairpin some other way, and
>> that's where things break down for me.  It may be a question of adjusting
>> springs and rods, but springs and rods are deep in the computational alchemy
>> of LilyPond, as far as I can see.
> 
> If you only care about adjusting the length of a hairpin without
> affecting the spacing, things are fairly simple (at least conceptually;
> actually writing the code might be a bit more challenging). You can get
> a list of (ordered by moment) paper columns from Paper_score. If you
> wait until after the page breaking is done, you can rely on the x-offset
> of these columns (which you get by
> paper_column->relative_coordinate(system,X_AXIS)) to be accurate. You
> could do a binary search for the moment you want and then do an
> interpolation if you don't find it. All of this is in the C++ code.
> 
> If you want to allow this length to affect the spacing, it's a bit more
> complicated because the spacing engine only allows you to mandate
> minimum space between two columns, so you somehow have to work backwards
> from the interpolation that you want to figure our how much space you
> need to reserve... but if you ignore this part, the only thing it will
> affect is the behaviour of 'minimum-distance, which probably isn't
> crucial.
> 
> Joe
>