Re: Did VerticalAxisGroup default-staff-staff-spacing stop respecting padding in 2.17.10?

[Keith OHara]

David Kastrup <dak <at> gnu.org> writes:

> With boxes, including baseline parts does not really make much of a
> difference, so the code could likely get away with treating empty and
> zero-extent as mostly equivalent.
> 
> With skylines, we don't have that luxury.  Stacking a zero-height box
> between skylines now makes a large difference.  And it would appear that
> there is code that is not aware of that difference yet.
> 

There might be a couple misunderstandings behind the text above.

Empty portions in skylines, such as the space between words in a Lyrics line,
do have height equal to -infinity, but in the implementation this makes the
empty portion transparent to the lines above and below.  Any collision between
skylines above and below is found correctly, even if it goes through a gap in
an intermediate line.  No difference between skylines and boxes in this regard.

Skylines do omit zero-width boxes (not zero-height boxes) and have done so
for a long time.  That omission seems to be a step in the problem with 
Trevor B's line of TimeSignatures, but I do not yet see the full causal path.

The reason for the omission of zero-width boxes is given as "numerical 
inaccuracies" in a code comment, but I see no case where a zero-with spike 
would cause any numerical-accuracy problem.