[smufl-discuss] Re: Glyph registration proposal

[Joseph Berkovitz]

> I am not sure if this should apply for clefs. My intuition is, that the clefs should be placed so, that the note that the clef refers to, is on the baseline (e.g. F-clef placed so, that one dot is above and the second below the baseline). Then, there would be no need for additional vertical adjustment for clef changes/cue clefs.  (Even if clef changes would be encoded, there are still cue clefs to be positioned correctly)

This idea also works (and is in fact the approach taken internally by Noteflight). But for clefs that don't refer to a "target note" such as TAB or percussion clefs, such a rule could become a bit arbitrary. So I don't have a strong feeling about it, either way.


>> TIME SIGNATURES
>>
>> The spec needs to stipulate that time signature digits are sized to fit
> I would add, that they should vertically centred on the baseline. Then, the scoring application draws them on the 4th (numerator) and 2nd (denominator) staff line (this behaviour should be possible to override by the user, e.g. for "handwritten" styles).
> It is because for very small staves, the staff lines are relatively thick, so the height (i.e. the size) of the digits should be adjusted so that the staff lines do not overshot the digits too much.

I agree with your point -- I think this was an oversight in my proposal. You are correct, time signature digits conceptually fit within a vertical extent, or are centered around some baseline.

>> FLAGS (U+E140–U+E15F)
>>
>> Currently flags' vertical position is dependent on their outline, which will vary unpredictably from font to font. Note that it is not possible to algorithmically determine the stem attachment point from a flag's bounding box.
>>
>> - All flags shall be vertically positioned so that the stem attachment point lies exactly on the font baseline at X=0. T (Note that it is possible for part of a flag to lie to the left of X=0 if it's drawn in a cursive fashion.)
> I would suggest something slightly different:
> Vertical position is related to the notehead that is placed on the first staff line (=on the font baseline), so that scoring app draws the glyph with no offset from the notehead (unless the stem is shortened when two voices occur). Please note that in different fonts the hemidemisemiquavers flags my require different stem length, so this positioning would make finding the appropriate stem length easier.
>
> For down-stem notes, the reference note head would be on the fifth staff line.
>

I don't favor any registration rules that "bake in" a standard stem length because there are so very many exceptions and adjustments to stem sizing and placement relative to note heads, many more than the multivoice case you mention. Stem length doesn't feel to me as though it should be part of the standard.

> Since stems have a non-zero width, an addition is needed, that the flag attachment point is in the middle of the stem width (there is some overlap needed to ensure that there will no gap between stem and flag, unless intentional)

This is true. I am planning to discuss this point in more detail in the metadata proposal, still TBD, since attachment points will need to be treated there.


>> RESTS (U+E1C0–U+E1DF)
>>
>> Rests are relative to an imaginary staff position, typographically speaking (usually the centerline of a 5-line staff in which the rest assumes its default position). The font baseline should represent this staff position. It is not possible to compute this position from a rest's bounding box, since it may not be the vertical center of the glyph. This implies that most of the rests will move vertically relative to where they are now so that the baseline provides information on where they appear relative to this "reference staff" line.  (If this list allowed attachments, I'd supply a figure here.)
>
> I think that they should be placed rather in reference to the font baseline, as if they were designed for one-line staff. This would simplify the placing of the rests when multiple voices occur on the same staff or in the different (orchestral) percussion staves.

I think this would also be a good change to my proposal.

.            .       .    .  . ...Joe

Joe Berkovitz
President

Noteflight LLC
Boston, Mass.
phone: [phone]
www.noteflight.com
"Your music, everywhere"
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