[smufl-discuss] Notehead Metrics

[Glenn Linderman]

Hi Daniel,

Not sure if my note regarding the suggestion for a unison whole notehead
came through.

But this note has a different purpose, to discuss the metrics for stem
attachment. Now I'm a programmer, not a font designer, so I don't know
much about how you figured out the numbers for the stem attachments, or
whether those points are specifically end points on the Bézier curves,
or just calculated to be tangent to the curves... in which case they
could appear to move around a bit at different resolutions.

So if I properly created a formula from your instructions, given the
point of placement of the note ( X, Y ) I should place the SW point of
an upward stem at:

( X + stemUpSE[0] - stemThickess,  Y + stemUpSE[1] )


When I did so, at larger sizes, it protruded awkwardly from the note.
So I "fiddled around" with the stemUpSE[0] numbers, until I got a stem
that was tangent to the note at the attachment point.

For noteheadHalf, this was 1.478, and for noteheadBlack, this was 1.443.
The Bravura metadata file suggests 1.364 and 1.328, respectively, with
the differences being .114 and .115, respectively. This is suspiciously
close to the stemThickness of .12, making me wonder if you accidentally
put StemUpSW values in the chart instead of StemUpSE values, as the
chart is labeled. These are the only noteheads I've experimented with so
far, so I can't say much in general terms, just these specific
noteheads. Using your numbers as StemUpSW values would work pretty well
for small notes, but for screen-filling notes, the values I determined
empirically work well for screen fonts from 10-2560pt.

Since screens are 96dpi and typesetters are around 2400dpi, this covers
typesetting up to 102pt... that'd be a large print edition!

I didn't test sizes between 2560 and 5120, but a spotcheck of 5120pt
size, my numbers produce stems that are well inside the notehead
boundaries :( So likely higher precision numbers (more than 3 digits to
the right of the decimal point) would be required to scale that high.


This raises my second question. While you recommend a staffLineThickness
of .13, I was experimenting with a staffLineThickness of .1, and even at
smaller zoom factors (anything above 17pt @96dpi) was noticing a little
protrusion of the notes both above and below the staff lines surrounding
the space they are sitting in.  Should the notes not be constrained to
the center point of the stafflines (or slightly less), rather than
exceeding the center points?


For reference, my testing was in using SVG graphics within the Firefox
web browser on Windows. The other Windows browsers seem to produce
similar results, although only Firefox properly handled the vertical
positioning ligatures of the BravuraText font. All of them (Firefox,
Opera, Chrome) can handle the Bravura font, positioned with SVG
graphics. Internet Explorer seems to have some issues with certain
operations of SVG graphics, so it produces somewhat bizarre results at
some zoom factors. I'm not sure what internal precision Firefox uses for
its graphics.

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