names of vertical spacing dimensions

[Mark Polesky]

Usually when I propose things like this, they're shot down
pretty fast, but here goes anyway.

It took me a while to mentally connect the names of the
vertical spacing variables with their specific domains.  For
example, I think it's counterintuitive that
'after-title-spacing does *not* affect the spacing after a
title when it's followed by another title or markup.  The
appropriate one for that is 'between-title-spacing.  Also,
some confusion arises before getting used to the fact that
markups are also referred to as "title".

Obviously not all markups are titles, but all titles are
markups, right?  Correct me if I'm wrong on that one, but if
I'm right, then I think that the variables should use
"markup" in place of "title".  Another convention that would
facilitate predictability is to use this form consistently:

  item1-item2-spacing

So 'between-system-spacing would be 'system-system-spacing.

Here's what I have so far.  I clipped the "-spacing"
suffixes for clarity:

CURRENT NAME           PROPOSED NAME
------------           -------------
top-system             top-system     (no change)
top-title              top-markup
between-title          markup-markup
after-title            markup-system
between-system         system-system
before-title           system-markup
bottom-system          (see below)
between-scores-system  (see below)


One wrinkle involves what is currently called
'bottom-system-spacing, since this applies both to systems
and markups, when either is the lowest item on the page.
Two options around this:

1) call it 'item-bottom-spacing or 'last-bottom-spacing or
   some such thing.
2) split it into 2 variables:
     'system-bottom-spacing, and
     'markup-bottom-spacing.

Also, I suppose 'between-scores-system-spacing would become
'score-score-spacing, and the new name loses some semantic
information: that it doesn't operate when a markup comes
between the systems.

Regardless, I prefer the consistency and predictability of
the proposed names.

Comments appreciated, thanks!
- Mark