Doc: Grobs without printed output on their own

[Simon Albrecht]

Hello,

as suggested by James, I come up with a suggestion on how to clarify the 
meaning of DynamicLineSpanner and similar.

1. In 
<http://lilypond.org/doc/v2.19/Documentation/learning/objects-and-interfaces>, 
insert the following after the fourth paragraph:
“What’s more, there are ‘abstract’ grobs which don’t print anything of 
their own, but rather collect, position and manage other grobs. Common 
examples for this are DynamicLineSpanner, BreakAlignment, NoteColumn, 
VerticalAxisGroup, NonMusicalPaperColumn and similar. We’ll see how some 
of these are used later.”

Other than that, I have no striking ideas on where to add information, 
especially in the NR. A table in the A.x attachment part wouldn’t be the 
right thing.
And subdividing IR 3.1 into ‘printing grobs’ and ‘abstract grobs’ would 
require major redesign, which is probably unnecessary.
So, just another idea of mine. I hope you don’t mind if I continue to 
post some thoughts which come to my mind. I know they are eccentrical 
and far from implementation reality sometimes and do not intend but to 
propose them to your judgement :-)

Best, Simon

Am 07.09.2014 um 00:23 schrieb James:
> On 06/09/14 21:17, Simon Albrecht wrote:
> > Am 06.09.2014 um 21:52 schrieb David Nalesnik:
> > > On Sat, Sep 6, 2014 at 1:52 PM, Joram <address@hidden
> > > <mailto:address@hidden>> wrote:
> > >
> > >
> > >      And I can add a question: What is the difference between
> > >      DynamicLineSpanner and Hairpin?
> > >
> > >
> > > See 
> > > http://lilypond.org/doc/v2.18/Documentation/internals/dynamic_005falign_005fengraver
> > >
> > > A DynamicLineSpanner is a grob which groups hairpins and dynamic texts
> > > so they can be lined up.
> > Perhaps it would be helpful to add a clear indication (in the IR, or
> > possibly in the NR?) stating that it doesn’t produce any visible output
> > on its own, or to group grobs by those who print something and those who
> > only collect and manage other grobs. I can imagine that this makes
> > understanding easier. And yes, I know that the Internals Reference may
> > not be modified as easily.
> Find a place in the NR where you think we need to add something and come
> up with some words, send it to the bug list and we can do the rest.
>
> James