[Lilypond-auto] Issue 3022 in lilypond: Documentation: NoteHead X-offset conflict with ly:grob-relative-coordinate

[lilypond]

Status: Accepted
Owner: ----
Labels: Type-Enhancement

New issue 3022 by address@hidden: Documentation: NoteHead X-offset  
conflict with ly:grob-relative-coordinate
http://code.google.com/p/lilypond/issues/detail?id=3022

Paul Morris reported here:

http://lists.gnu.org/archive/html/bug-lilypond/2012-12/msg00013.html

as follows:

> I'm not top posting.

% All the notes should be moved to the right-hand
% side of the stem by overriding their X-offset
% property, but something about the "rel-coord"
% variable that is set by "ly:grob-relative-coordinate"
% prevents this from working as it should.  After
% removing that variable it works fine. Setting
% X-extent also does not work (this is commented
% out below).

\version "2.16.1"

CustomNoteHeads =
#(lambda (grob)
  (let* (
    (notecol (ly:grob-parent grob 0))
    (rel-coord (ly:grob-relative-coordinate grob notecol 0)))
    (set! (ly:grob-property grob 'X-offset) 1.251178 )

    ;; (set! (ly:grob-property grob 'X-extent) '(0 . 4) ))
)

\score {
  \new Staff
    \with {
      \override NoteHead #'before-line-breaking = \CustomNoteHeads
    }
    { c' d' e' f' }
  \layout { }
}

In response to that Keith O'Hara and Thomas Morley explained that this was  
not a bug. The outcome is a documentation enhancement request as set out  
here by Paul Morris:

http://lists.gnu.org/archive/html/bug-lilypond/2012-12/msg00034.html

Quoting part of that posting:

> NR 5.5.1 Aligning objects:

> Note: Many objects have special positioning considerations which cause
> any setting of X-offset or Y-offset to be ignored or modified, even
> though the object supports the self-alignment-interface. Overriding
> the X-offset or Y-offset properties to a fixed value causes the
> respective self-alignment property to be disregarded.

> http://lilypond.org/doc/v2.17/Documentation/notation/aligning-objects

Ah, ok, so that page is already documenting this.


> But I found no hint about it in the IR

Would it make sense if under "X-offset" in the IR it said something like  
this?

"The horizontal amount that this object is moved relative to its X-parent.   
The
amount may be set directly or may be set to be calculated by procedures in
order to achieve alignment with the parent object."

(Added a borrowed sentence from the page linked above.)

Cheers,
Colin.