A metacomment on Re: Text spanner shorten-pair

[David Wright]

Can I just point out that, whether you top-post or bottom-post,
it's nearly impossible to follow the conversation in the plain text
version of this post because there's no indication of quoting.

On Wed 13 Feb 2019 at 14:33:39 (+0000), Carl Sorensen wrote:
> 
> 
> From: Trevor Bača <address@hidden>
> Date: Wednesday, February 13, 2019 at 6:43 AM
> To: Carl Sorensen <address@hidden>
> Cc: Andrew Bernard <address@hidden>, lilypond-user Mailinglist 
> <address@hidden>
> Subject: Re: Text spanner shorten-pair
> 
> 
> 
> On Tue, Feb 12, 2019 at 6:12 PM Carl Sorensen 
> <address@hidden<mailto:address@hidden>> wrote:
> 
> 
> From: Trevor Bača <address@hidden<mailto:address@hidden>>
> Date: Tuesday, February 12, 2019 at 3:09 PM
> To: Carl Sorensen <address@hidden<mailto:address@hidden>>
> Cc: Andrew Bernard <address@hidden<mailto:address@hidden>>, lilypond-user 
> Mailinglist <address@hidden<mailto:address@hidden>>
> Subject: Re: Text spanner shorten-pair
> 
> On Fri, Jan 25, 2019 at 11:38 AM Carl Sorensen 
> <address@hidden<mailto:address@hidden>> wrote:
> 
> Question: why are there two ways to move around the ends of spanners (padding 
> vs. shortening)? I can't think of a reason that's motivated by music notation.
> 
> Padding is a minimum amount of blank space between two pieces of ink on the 
> page.  When a pedal bracket is running into empty space, it doesn’t matter 
> what the padding setting is, because there is no ink for it to move away 
> from.  Padding says “don’t just avoid collisions; leave a minimum amount of 
> empty space in addition to avoiding collisions”.  There’s no collision to 
> avoid between a pedal bracket and its associated note column.
> 
> Ok, wow, this is actually hugely interesting. Thank you so much for the 
> specificity of the first part of the answer: "Padding is a minimum amount of 
> blank space between two pieces of ink on the page." That is actually 
> genuinely new information to me about a small-but-pervasive concept in 
> LilyPond. Right up until just now, I had assumed that padding meant "a 
> minimum amount of blank space between TWO THINGS on the page (whether the 
> things are visible or not)"; we are hugely concerned with the (frequently 
> invisible) start- and stop-anchors of things when engraving objects in score; 
> and I had incorrectly assumed that padding at the edges of, say, a piano 
> pedal bracket would pad between the invisible start-anchor of the bracket 
> (which you described earlier as some flavor of column) and the visible start 
> of the bracket itself. This is apparently not the case.
> 
> I think that I was incorrect in saying “ink on the page”, although that is 
> the intent of padding.  I should have said “between two bounding boxes”.  One 
> way to make spanners respect padding would be to increase the vertical extent 
> of the bounding box (but that comes with a cost of preventing markups from 
> sitting above or below the bounding box.
> 
> This probably explains a small part of why I may have found the spacing 
> behavior of piano pedal brackets flakey, to a certain extent, for well over a 
> decade.
> 
> So my surprise here (that the Lily concept of "padding" won't pad between the 
> invisible anchors of things that I'm always mentally tracking when I work), 
> makes me think that this surprisingly-restricted (at least to me ;) model of 
> padding is possibly a "mis-model" in the system, or maybe a not-yet-realized 
> possibility for a more complete generalization of what spanners are.
> 
> I think that you have hit on an important fundamental that is not properly 
> represented in LilyPond.  Spanners might be properly said to be anchored to 
> note columns *regardless* of whether they have anything in them at a 
> particular vertical location.  Maybe the spacing algorithms for spanners 
> should assume a note-column with infinite vertical extents….
> 
> 
> Thanks for your good thoughts about this.
> 
> Carl

Cheers,
David.