Re: Issue 3330: redo much of the stencil stacking/spacing/empty-check (issue 8869044)

[Keith OHara]

On Mon, 06 May 2013 03:21:18 -0700, David Kastrup <address@hidden> wrote:

"Keith OHara" <address@hidden> writes:

Oh. I thought it was good.  If the possibly-backspaced cursor is
forgotten when \line is finished, then the user doesn't have to
remember where the cursor ended up.

Why would he backspace when he doesn't mean it?

I was thinking of something like this, where you want to backspace to place a 
graphic, but then use the whole extent of the overlaid text for spacing the 
line :

\markup { A
 \line {reverse turn \hspace#-5 \raise #2 \musicglyph #"scripts.reverseturn" }
 is found in the original manuscript.}

Another case would be  symbol = \markup { \hspace#-1 \char ##x2230 }
where the \hspace gives somebody's desired alignment over music, but \symbol is 
also used as a word in text.

It looks very good that you made 'empty' mean (+inf . inf) so that
negative extents don't count as empty.  But then defining 'half-empty'
complicates things again, and I have not found a use for it.

Uh, reality check?  It fixes the hspace/concat bug you encountered
elsewhere in a clean manner, it lets page numbers in table of contents
actually appear flush to the right (like the page number in the page
headings does), it makes \hspace add a predictable amount of space, it
makes indentations at the start of auto-filled paragraphs remain rigid
rather than being expanded along with other spaces...

Any way of flagging the stencil made by \hspace as purely spacing, so that it 
doesn't get 'word-space around it, would have those nice effects.  Half-empty 
extents are an awkward way to flag the stencil, especially when its empty 
stencil-expression is a more-easily understandable flag.

Your comments at the start of Stencil::add_at_edge() seem to indicate that you 
find the interface awkward, and I would agree, so I was pushing for other 
solutions.  I'll stop.