Re: Possible bug(s) with vertical alignment on Dynamics staff

[Malte Meyn]

Hi Peter,

have you read my latest answer on the user list? 
(https://lists.gnu.org/archive/html/lilypond-user/2018-08/msg00412.html)

Am 31.08.18 um 13:36 schrieb Peter Toye:
> 1. Just inserting the text by attaching it to a silent note using "^" or "_" works 
> as expected. See examples 1 & 2

I suppose that’s not one of your “possible bugs”, is it? ;)

> 2. Trying "-" is the same as "_". This isn't documented, and probably shouldn't 
> be. But it would be useful to have this syntax for horizontally aligned text. See example 3.

_ and ^ set the direction property of an Event (in this case a 
TextScriptEvent) to #DOWN and #UP. “-” doesn’t set it at all—this means 
that LilyPond decides whether to set it down or up depending on 
different things (type of grob, voice direction in polyphony, …). Your 
suggestion would mean that “-” sets the direction to #CENTER. This isn’t 
supported at the moment, it’ll throw an error (you can try that: 
\override TextScript.direction = #CENTER).

Now what should #CENTER behave like? If there is some space like in your 
example, your suggestion is legitimate IMO. But in most cases one has 
only two options, up and down (f. e. think of articulations). Letting 
“-” set the direction to #CENTER, even if #CENTER would mean “automatic 
default behaviour” would be wrong because direction information coming 
from \voiceX commands would be overridden.

> 3. Tweaking the Y-offset by 0.0 using "_" appears to change it to having used 
> "^" if you see what I mean. Example 4. Tweaking it to -0.6 gives the result I want. 
> Example 5.

The Y-offset is calculated (see my answer to 4. below) depending on 
different things including the 'direction property. So if you tweak the 
Y-offset, the direction will be ignored (at least for the positioning 
question).

> 4. In the Internals manual, the unit for the Y-offset property is not 
> mentioned. This wastes a lot of time in experimentation, especially given issue 
> 3!

What do you mean by unit? Yes, the IR 
(http://lilypond.org/doc/v2.19/Documentation/internals/user-backend-properties) 
doesn’t say whether Y-offset is measured in staff-spaces, half 
staff-spaces or some different unit. But I suppose you mean “value” 
here? That value is calculated by a procedure that uses information 
about the context (type of grob, neighbouring grobs, font sizes, line 
breaks, voice direction, …). That’s why the manual cannot give the 
default value as a number—there is no such thing as a default value.

I hope I made clear what the problems are here. If not, just ask ;) (And 
have a look at the \offset command I mentioned on the user list :))

Cheers,
Malte