glyph placement does not use font baseline

[Kieren MacMillan]

Hello, all --

The following example finally clarifies something that has been  
nagging at me for a while, but I've never been able to figure out  
exactly why...

Note how the markup is placed: not according to the baseline of the  
font, but according to the extreme edge of each particular glyph  
(e.g., bottom of 'p' descender, top of the 'b' ascender), and thus  
how the 'n', 'p', 's', and 'b' in the example do not rest on the same  
baseline, even though the padding (placement) would lead one to  
believe they should. [The same is true of dynamic markup text,  
obviously, which is where this irritation first became apparent to me.]

I really think this should be fixed -- all other graphics/layout  
programs I've used consider the font baseline as the anchor point for  
glyph placement, which naturally leads to a more consistent user  
(and, probably, programmer) experience.

I'm happy to hunt down the culprit and fix it myself, but I need to  
know whether it's
    1. a font problem (fixed in metafont or FontForge?);
    2. a PostScript problem (fixed in C++ code?);
    3. a Lilypond layout problem (fixed in Scheme?); or,
    4. some combination of #1-3.

Any thoughts?

Thanks,
Kieren.

___________________________________________

%%% CODE SNIPPET BEGINS
\version "2.9.7"

pFour = \once \override TextScript #'padding = #4
sFour = \once \override TextScript #'staff-padding = #4

\paper
{
        indent = 0
        line-width = 5.5\in
        ragged-bottom = ##t
}

\relative c'
{
        f4^"n" \pFour f^"p" \sFour f^"s" \pFour\sFour f^"b"
        g,4^"n" \pFour g^"p" \sFour g^"s" \pFour\sFour g^"b"
        f'4_"n" \pFour f_"p" \sFour f_"s" \pFour\sFour f_"b"
        d''4_"n" \pFour d_"p" \sFour d_"s" \pFour\sFour d_"b"
}
%%% CODE SNIPPET BEGINS