Re: Some things need need to be fixed on the interfaces pages

[Saul Tobin]

I mean should MMRs actually use centered-spanner-interface? MMRs are after all spanners that are centered between spacing-pair. It looks to me like the C++ code for MMRs does exactly the same offset calculation as centered-spanner-interface::calc-x-offset, though not all in one place.

On Tue, Dec 10, 2024, 11:38 PM Werner LEMBERG <wl@gnu.org> wrote:

>> The policy of LilyPond is to avoid different property names for
>> similar functionality, which often leads to cryptic property
>> descriptions to be as generic as possible.  In this particular case
>> an example is given, which is actually a good thing, but it doesn't
>> cover the `centered-spanner-interface` incarnation of this
>> property.
>>
>> Maybe you can suggest a better wording for the description of
>> `spacing-pair`?
>> [...]
>
> On the centered-spanner-interface page, the comment about the
> MultiMeasureRest can just be deleted (as it's already on the
> multi-measure-interface page, as long as the description of
> spacing-pair is correct.

Exactly this is not possible, because there exists only a single,
global property called `spacing-pair`, which consequently has a
single, global description.

In other words, the auto-generated documentation sees that an
interface uses `spacing-pair`, and it shows its description.

IIRC, a suggestion in the mentioned thread is to make the property
description displayed for a given grob show which interfaces it is
part of, for example

```
‘spacing-pair’ (pair)
     interface(s):
          centered-spanner-interface, multi-measure-interface
     default value:
          '(break-alignment . break-alignment)

     A pair of alignment symbols which set an object's spacing
     relative to its left and right ‘BreakAlignment’s.

     For example, a ‘MultiMeasureRest’ will ignore prefatory items
     at its bounds (i.e., clefs, key signatures and time
     signatures) using the following override:

          \override MultiMeasureRest.spacing-pair =
                       #'(staff-bar . staff-bar)
```

On the description page for `centered-spanner-interface` it could
display the following:

```
‘spacing-pair’ (pair)
     also used in:
          multi-measure-interface

     A pair of alignment symbols which set an object's spacing
     relative to its left and right ‘BreakAlignment’s.

     For example, a ‘MultiMeasureRest’ will ignore prefatory items
     at its bounds (i.e., clefs, key signatures and time
     signatures) using the following override:

          \override MultiMeasureRest.spacing-pair =
                       #'(staff-bar . staff-bar)
```

>> What instrument(s) do you have in mind?  It is possible to improve
>> the description while talking about 'left hand' and 'right hand' in
>> the context of fretted instruments, but I don't think it makes
>> sense to change these long-established terms.
>
> The main instrument I'm thinking of is the guitar.

OK, I see.  The probably simplest solution is to explicitly mention
that LilyPond uses the term 'right hand' to actually indicate the
strumming hand.

> And there's actually precedent, in that left-handed chord diagrams
> (FretBoards) are supported by Lilypond.

Well, this makes sense, because they are displayed differently.


    Werner