Clef positions

[Peter Chubb]

>>>>> "Han-Wen" == Han-Wen Nienhuys <address@hidden> writes:

Me> ...
Me> 
Me> But the clefPosition seems strange to me -- If I set it to 2 to
Me> get, say, an F clef on the second line, the clef comes out on the
Me> fourth line.  I suspect from experiment that Y-position here
Me> doesn't mean staffline, but offset from the middle of the staff.

Han-Wen> yes. Vertical positions are always measured from the center
Han-Wen> of the staff. (that's the only sane way, nice and symmetric).

In modal notation (which Lily doesn't handle yet), and in the 15th
century Mannerist notations, the number of staff lines can change from
time to time..  For example, in the FitzWilliam MS 168, page 314,
there's a 6 line staff that has an F clef on line 4, which turns into
a 7 line staff, without moving the clef (the extra line is above the staff).

(I'm not suggesting that Lily  supports this, only to say that setting
clef positions based on counting lines from the bottom makes sense --
especially as a clef is always on a line, never on a space).

>> And surely a clef needs four parameters, anyway: -- the glyph --
>> which note it represents (currently only C F or G)

Han-Wen> the note that a clef represents follows from the glyph
Han-Wen> (otherwise, clefs would not be very useful, would they?)

This means that the correspondence glyph<->pitch is hardcoded
somewhere (Ah -- I've found it -- in the ScoreContext in engraver.ly)


All this is because the output of ancient-font.ly looks weird.  And
I've found the answer --- for some reason in 1.3.137  \property
Staff.StaffSymbol \override #'line-count = #4 is ignored, so the clefs
arrive at a space instead of on the appropriate line.

Peter C