[lilypond.git] / scm / grob-property-description.scm

;;;; grob-property-description.scm -- part of generated backend documentation
;;;;
;;;;  source file of the GNU LilyPond music typesetter
;;;; 
;;;; (c) 1998--2001  Han-Wen Nienhuys <hanwen@cs.uu.nl>
;;;;                 Jan Nieuwenhuizen <janneke@gnu.org>



(define all-backend-properties '())

(define (grob-property-description symbol type? description)
  (if (not (equal? (object-property symbol 'backend-doc) #f))
      (begin
        (ly-warn (string-append "Redefining " (symbol->string symbol) "\n"))
        (exit 2)
      ))
  
  (set-object-property! symbol 'backend-type? type?)
  (set-object-property! symbol 'backend-doc description)
  (set! all-backend-properties (cons symbol all-backend-properties))
  )

;; put this in an alist?

(grob-property-description 'X-extent-callback procedure? "procedure taking an grob and axis argument, returning a number-pair. The return value is the extent of the grob.

The size of a grob are determined through callbacks, settable with
grob properties @code{X-extent-callback} and @code{Y-extent-callback}.
There can be only one extent-callback for each axis. No callback
(Scheme value @code{#f}) means: `empty in this direction'. If you fill
in a pair of numbers, that pair hard-codes the extent in that
coordinate.
")
(grob-property-description 'X-offset-callbacks list? "list of functions, each taking an grob and axis argument. The function determine the position relative to this grob's parent. The last one in the list is called first.

Offsets of grobs are relative to a parent reference point. Most
positions are not known when an object is created, so these are
calculated as needed. This is done by adding a callback for a specific
direction.

Offset callbacks can be stacked, i.e.

@example
        \property .... \override #'Y-offset-callbacks = #(list
                callback1 callback2 callback3)

@end example

The callbacks will be executed in the order @code{callback3 callback2
callback1}. This is used for quantized positioning: the staccato dot is
above or below a note head, and it must not be on a staff-line.  To
achieve this, the staccato dot has two callbacks: one that positions the
grob above or below the note head, and one that rounds the Y-position of
the grob to the nearest open space.


")
(grob-property-description 'Y-extent-callback procedure? "see @code{X-extent-callback}.")
(grob-property-description 'Y-offset-callbacks list? "see @code{X-offset-callbacks}.")

(grob-property-description 'accidental-grobs list? "Alis with (NOTENAME . GROBLIST) entries")
(grob-property-description 'accidentals list? "List of alteration numbers.")
(grob-property-description 'add-stem boolean? "Add stem to porrectus?.")
(grob-property-description 'adjust-if-on-staffline boolean? "If this grob is on a staff line, adjust its appearance, so that it better fits into the staff.  E.g., if set true on stem grobs, flares of mensural flags will always be aligned with the staff lines, regardless if the associated note head is printed on a staff line or inbetween.")
(grob-property-description 'after-line-breaking-callback procedure? "Procedure taking a grob as argument.
This procedure is called (using dependency resolution) after line breaking. Return value is ignored.")
(grob-property-description 'align number? "the alignment of the text, 0 is horizontal, 1 is vertical.")
(grob-property-description 'align-dir dir? "Which side to align? -1: left side, 0: around center of width, 1: right side.")
(grob-property-description 'alignment-done boolean? "boolean to administrate whether we've done the alignment already (to ensure that the process is done only once).")
(grob-property-description 'all-elements grob-list? "list of all grobs in this line. Needed for protecting grobs from GC.")
(grob-property-description 'arch-angle number? "turning angle of the hook of a system brace" )
(grob-property-description 'arch-height number? "height of the hook of a system brace.")
(grob-property-description 'arch-thick number? "thickness of the hook of system brace.")
(grob-property-description 'arch-width number? "width of the hook of a system brace.")
(grob-property-description 'arpeggio ly-grob? "pointer to arpeggio object.") 
(grob-property-description 'arpeggio-direction dir? "If set, put an
arrow on the arpeggio squiggly line.")
(grob-property-description 'attachment pair? "cons of symbols
indicating how a slur should be attached at the ends. The format is
'(LEFT-TYPE . RIGHT-TYPE), where both TYPEs are symbols. The values of
these symbols may be alongside-stem, stem, head or loose-end.")
(grob-property-description 'attachment-offset pair? "cons of offsets,
'(LEFT-offset . RIGHT-offset).  This offset is added to the
attachments to prevent ugly slurs.  [fixme: we need more documentation here].
.")
(grob-property-description 'auto-properties boolean? "if true, as many properties of this grob as possible will be determined automatically from the musical context.")
(grob-property-description 'auto-knee-gap number? "If a gap is found between noteheads
where a  horizontal beam fits that is larger than this number,  make a kneed beam.")
(grob-property-description 'axes list? "list of axis numbers.
In the case of alignment grobs, this should contain only one number.")
(grob-property-description 'bar-size number? "size of a bar line.")
(grob-property-description 'bars grob-list? "list of barline pointers.")
(grob-property-description 'bar-size-procedure procedure? "Procedure that computes the size of a bar line.")
(grob-property-description 'base-shortest-duration moment?
                           "Spacing is based on the shortest notes in a piece. Normally, pieces are spaced as if notes at least as short as this are present.")
(grob-property-description 'baseline-skip number? "Baseline skip to use for multiple lines of text.")
(grob-property-description 'bass list? " musical-pitch, optional.")
(grob-property-description 'beam ly-grob? "pointer to the beam, if applicable.")
(grob-property-description 'beam-thickness number? "thickness, measured in staffspace.")
(grob-property-description 'beam-width number? "width of the tremolo sign.")
(grob-property-description 'beamed-lengths list? "list of stem lengths given beam multiplicity .")
(grob-property-description 'beamed-minimum-free-lengths list? "list of normal minimum free stem lengths (chord to beams) given beam multiplicity.")
(grob-property-description 'beamed-extreme-minimum-free-lengths list? "list of extreme minimum free stem lengths (chord to beams) given beam multiplicity.")
(grob-property-description 'beamed-stem-shorten list? "shorten beamed stems in forced direction.")
(grob-property-description 'beaming pair?
                           "Pair of number lists. Each number list
specifies which beams to make. 0 is the central beam, 1 is the next
beam toward the note etc. This information is used to determine how to
connect the beaming patterns from stem to stem inside a beam.")


(grob-property-description 'beautiful number? "number that dictates when a slur should be de-uglyfied.  It correlates with the enclosed area between noteheads and slurs.  A value of 0.1 yields only undisturbed slurs, a value of 5 will tolerate quite high blown slurs.")
(grob-property-description 'before-line-breaking-callback procedure? "Procedure taking grob as argument.
This procedure is called (using dependency resolution) before line breaking, but after generating discretionary items. Return value is ignored.")
(grob-property-description 'between-cols pair? "Where to attach a loose column to")
(grob-property-description 'between-system-string string? "string
 to dump between two systems. Useful for forcing pagebreaks.")
(grob-property-description 'bounded-by-me grob-list? "list of spanners that have this
column as start/begin point. Only columns that have grobs or act as bounds are spaced.")
(grob-property-description 'bracket-thick number? "width of a system start bracket. .")
(grob-property-description 'break-align-symbol symbol? "the index in the spacing table (symbol) of the to be aligned item.")
(grob-property-description 'break-glyph-function procedure? "function taking glyph and break-direction, returning the glyph at a line break.")
(grob-property-description 'breakable boolean? "boolean indicating if this is a breakable item (clef, barline, key sig, etc.).")
(grob-property-description 'c0-position integer? "integer indicating the position of central C.")
(grob-property-description 'cautionary-style symbol? "style  of cautionary accidentals. Choices are 'smaller (one size smaller) or 'parentheses.")
(grob-property-description 'center-element ly-grob? "grob which will
be at the center of the group after aligning (when using
Align_interface::center_on_element). .")
(grob-property-description 'concaveness-gap number? "A beam is
considered to be concave if the distance of an inner notehead to the
line between two outer noteheads is bigger than this gap.")
(grob-property-description 'concaveness-threshold number? "A beam is
considered to be concave is concaveness is bigger than this threshold.
Concaveness is calculated as the sum of the vertical distances of
inner noteheads that fall outside the interval of the two outer
noteheads, to the vertically nearest outer notehead, divided by the
square of the inner notes involved.")
(grob-property-description 'collapse-height number? "Minimum height of system start delimiter.  If equal or smaller, the bracket is removed.")

(grob-property-description 'columns grob-list? "list of grobs, typically containing paper-columns.")
(grob-property-description 'conditional-elements grob-list? "Internal use only")
(grob-property-description 'control-points list? "List of 4 offsets (number-pairs) that form control points for the  tie/slur shape.")
(grob-property-description 'damping integer? "amount of beam slope damping should beam slope be damped? 0: no, 1: yes, 100000: horizontal beams .")
(grob-property-description 'dash-length number? "the length of a dash.")
(grob-property-description 'dash-period number? "the length of one dash + white space.")
(grob-property-description 'dashed number? "[FIXME: use dash-period/dash length; see text-spanner] number representing the length of the dashes.")
(grob-property-description 'de-uglify-parameters list? "list of 3 real constants. They define the valid areas for the middle control points. Used in de_uglyfy. They are a bit empirical.")

(grob-property-description 'neutral-direction dir? "Where to go if we're on the neutral position of the staff (by default, the middle of the staff; see also grob-property neutral-position).  [Ross] has the following to say about this: Some engravers consider the middle line neutral, and take the option of using either up- or down-stems for notes that fall on it. However, more up-to-date engraving no longer permits an option; now a down-stem is always appropriate.")
(grob-property-description 'neutral-position number? "Position (in half staff spaces) where to flip the direction of stems: by default, custodes above this position get their stems downwards; custodes below this position get their stems upwards.  A value of 0 designates the center of the staff.  Use property neutral-direction to control the behaviour of stems on the neutral position itself.  (Note: currently, neutral-position is supported only for custodes; for stems of note heads, neutral-position is currently fixed to 0, i.e. the middle of the staff.)")
(grob-property-description 'dependencies grob-list? "list of score-grob pointers that indicate who to compute first for certain global passes.")
(grob-property-description 'details list? "alist of parameters for detailed grob behavior.")
(grob-property-description 'dir-function procedure? "function of type (count total)->direction.  Default value: beam-dir-majority, also available: beam-dir-mean, beam-dir-median.

The ways to calculate the direction of a beam work as follows:
@table @code
@item majority
number count of up or down notes
@item mean
mean center distance of all notes
@item median
mean centre distance weighted per note
@end table

")
(grob-property-description 'direction dir? "up or down, left or right?.")
(grob-property-description 'direction-source ly-grob? "in case side-relative-direction is set, which grob  to get the direction from .")
(grob-property-description 'dot ly-grob? "reference to Dots object.")
(grob-property-description 'dot-count integer? "number of dots.")
(grob-property-description 'duration-log integer? "2-log of the notehead duration, i.e. 0=whole note, 1 = half note, etc.")
(grob-property-description 'edge-height pair? "a cons that specifies the heights of the vertical edges '(LEFT-height . RIGHT-height).")
(grob-property-description 'edge-widen pair? "a cons that specifies the widths of the slanted edges '(LEFT-width . RIGHT-width).")
(grob-property-description 'edge-text pair? "a cons that specifies the texts to be set at the edges '(LEFT-text . RIGHT-text).")
(grob-property-description 'elements grob-list? "list of grobs, type depending on the Grob where this is set in.")
(grob-property-description 'expand-limit integer? "maximum number of measures expanded in church rests.")
(grob-property-description 'extra-X-extent number-pair? "enlarge in X dimension by this much, measured in staff space.")
(grob-property-description 'extra-Y-extent number-pair? "see @code{extra-Y-extent}.")
(grob-property-description 'X-extent number-pair? "Store extent. internal use only. ")
(grob-property-description 'Y-extent number-pair? "Store extent. internal use only. ")
(grob-property-description 'extra-offset number-pair? "pair of reals
(a cons) forcing an extra offset before outputting.
@code{extra-offset} is added just before `printing' the grob, so the
typesetting engine is completely oblivious to it.
")
(grob-property-description 'extremity-offset-alist list? "an alist (attachment stem-dir*dir slur-dir*dir) -> offset.  The offset adds to the centre of the notehead, or stem.")

(grob-property-description 'extremity-rules list? "an alist (procedure
slur dir) -> attachment to determine the attachment (see above).  If
procedure returns #t, attachment is used.  Otherwise, the next
procedure is tried.")
(grob-property-description 'flag-style string? "set to \"grace\" to turn stroke through stem on.")
(grob-property-description 'flag-width-function procedure? "Procedure that computes the width of a half-beam (a non-connecting beam.).")
(grob-property-description 'flexa-width number? "width of a flexa shape in a ligature grob.")
(grob-property-description 'font-family symbol? "partial font
definition: music roman braces dynamic math ...")
(grob-property-description 'font-name string? "file name for the font to load.
Overrides all other font-X qualifiers.")
(grob-property-description 'font-design-size number? "partial font definition: exact font size in points FIXME: should override font-relative-size.")
(grob-property-description 'font-magnification number? "Magnification
  of the font. If undefined, the default is @code{1.0}.")
(grob-property-description 'font-relative-size number? "partial font definition: the relative size compared the `normal' size.
 0 is style-sheet's normal size, -1 is smaller, +1 is bigger, -1 is smaller.")
(grob-property-description 'font-series symbol? "partial font definition: medium, bold.")
(grob-property-description 'font-shape symbol? "partial font definition: upright or italic.")

(grob-property-description 'font-style symbol? "a precooked set of font
definitions, eg. finger volta timesig mark script large Large
dynamic.")

(grob-property-description 'force-hshift number? "amount of
collision_note_width that overides automatic collision settings. This
is used by @ref{note-collision-interface}.")

(grob-property-description 'fraction number-pair? "fraction of a time signature.")
(grob-property-description 'french-beaming boolean? "Use French
beaming style: stems stop at innermost beams.")
(grob-property-description 'full-size-change boolean? "if set, don't make a change clef smaller.")

(grob-property-description 'glyph string? "a string determining what (style) of  glyph is typeset. Valid choices depend on the function that is reading this property. .")
(grob-property-description 'glyph-name string? "a name of character within font.")

(grob-property-description 'gap number? "Size of a gap in a variable symbol.")

(grob-property-description 'grow-direction dir? "crescendo or decrescendo?.")
(grob-property-description 'hair-thickness number? "thickness, measured in stafflinethickness.")
(grob-property-description 'heads pair? "Pair of grob pointers, pointing to the two heads of the  tie.")
(grob-property-description 'height number? "in staffspace.")
(grob-property-description 'height-limit number? "Maximum slur height,
  long slurs approach this height.

  For small width w, the height should be proportional to w, for w ->
  infinity, the height should rise to limit h_infinity asymptotically.

  Hence we take F (x) such that
@quotation
@example  
  F (0) = 0 , F' (0) = 1, and F (infinity) = 1
@end example
@end quotation
  where
@quotation
@example  
  h = height-limit * F (x * ratio / height-limit)
@end example
@end quotation
  Currently, for F we use
@quotation
@example  
  F (x) = 2/pi * atan (pi * x/2)
@end example
@end quotation
")
(grob-property-description 'horizontal-shift integer? "integer that identifies ranking of note-column for horizontal shifting. This is used by @ref{note-collision-interface}.")
(grob-property-description 'ideal-distances list? "(OBJ . (DIST . STRENGTH)) pairs.")
(grob-property-description 'interfaces list? "list of symbols indicating the interfaces supported by this object. Is initialized from the @code{meta} field.")
(grob-property-description 'inversion list? " musical-pitch, optional.")
(grob-property-description 'items-worth-living grob-list? "list of interesting items. If empty in a particular system, clear that system.")
(grob-property-description 'join-heads boolean? "Whether to join the noteheads of an ambitus grob with a vertical line.")
(grob-property-description 'kern number? "amount of extra white space to add.

For text,  this is `relative'(?) to the current alignment.

For barline, space after a thick line.")
(grob-property-description 'knee-spacing-correction number? "optical correction amount for knees. 0: no correction; 1: full correction.")
(grob-property-description 'layer number? "The output layer [0..2].  The default is 1.")

(grob-property-description 'left-position number? "position of left part of spanner.")
(grob-property-description 'right-position number? "position of right part of spanner.")
(grob-property-description 'left-padding number? "space left of accs.")
(grob-property-description 'right-head ly-grob? "")
(grob-property-description 'left-head ly-grob? "")

(grob-property-description 'left-widen boolean? "Whether the left edge of a piano pedal bracket should be widened by the first element of edge-widen.")

(grob-property-description 'length number? "Stem length for unbeamed stems, only for user override.")
(grob-property-description 'lengths list? "Stem length given
multiplicity of flag.  The Nth element of the list gives the stem
length of a note with N flags.
")
(grob-property-description 'line-count integer? "Number of staff
lines.  If you want to override this for staffs individually, you must
use @code{\outputproperty}. @code{\property .. \override} will not
work: @code{\override} is processed after the StaffSymbol is created,
and will have no effect.
")
(grob-property-description 'lookup symbol? "lookup method: 'value for plain text, 'name for character-name.")
(grob-property-description 'magnify number? "the magnification factor.  FIXME: doesn't work for feta fonts.")
(grob-property-description 'maximum-length number? "don't make Grob longer than this")
(grob-property-description 'maximum-rest-count integer? "kill off rests so we don't more than this number left.")
(grob-property-description 'measure-length moment? "Length of a
measure. Used in some spacing situations.")
(grob-property-description 'measure-count integer? "number of measures for a multimeasure rest.")

(grob-property-description 'merge-differently-headed boolean? "Merge
noteheads in collisions, even if they have different note heads. The
smaller of the two heads will be rendered invisible. This used
polyphonic guitar notation. The value of this setting is used by
@ref{note-collision-interface} .")

(grob-property-description 'merge-differently-dotted boolean? " Merge
noteheads in collisions, even if they have a different number of
dots. This normal notation for some types of polyphonic music. The
value of this setting is used by @ref{note-collision-interface} .")

(grob-property-description 'meta list? "Alist of meta information of this grob.

The alist contains the following entries: name, interfaces.



")
(grob-property-description 'minimum-distance number? "minimum distance between notes and rests.")
(grob-property-description 'minimum-distances list? "list of rods (ie. (OBJ . DIST) pairs).")

(grob-property-description 'minimum-X-extent number-pair? "minimum size in X dimension, measured in staff space.")
(grob-property-description 'minimum-Y-extent number-pair? "see @code{minimum-Y-extent}.")
(grob-property-description 'minimum-length number? "try to make the
Grob at least this long.

Also works as a scaling parameter for the length of hyphen. .")

;; FIXME.
(grob-property-description 'minimum-space number? "minimum distance that the victim should move (after padding).

FIXME: also pair? (cons LEFT RIGHT)

")
(grob-property-description 'molecule-callback procedure? "Function
taking grob as argument, returning a smobbed Molecule.

All visible, i.e. non-transparent, grobs have a callback to create a
Molecule. The callback should be a Scheme function taking one argument
(the grob) and returning a Molecule.  Most molecule callbacks are
written in C++, but you can also write them in Scheme. An example is
provided in @code{input/regression/molecule-hacking.ly}.
")

(grob-property-description 'molecule molecule? "Cached output of the molecule-callback.")

(grob-property-description 'new-accidentals list? "list of (pitch, accidental) pairs.")
(grob-property-description 'no-spacing-rods boolean? "read from grobs: boolean that makes Separation_item ignore this item (MOVE ME TO ITEM).")
(grob-property-description 'no-stem-extend boolean? "should stem not be extended to middle staff line?.")
(grob-property-description 'non-default boolean? "not set because of existence of a bar?.")
(grob-property-description 'note-head-style string? "name of the font character to be used as note heads in the ambitus grob.")
(grob-property-description 'note-heads grob-list? "List of note head grobs")
(grob-property-description 'number-threshold number? "only put numbers bigger than this threshold over multi measure rest.")
(grob-property-description 'old-accidentals list? "list of (pitch, accidental) pairs.")
(grob-property-description 'outer boolean? "whether a text spanner should extend to the outer edge of the spanned notes")
(grob-property-description 'padding number? "add this much extra space between objects that are next to each other.")
(grob-property-description 'pedal-type symbol? "Style of piano pedal: text, bracket or mixed.")
(grob-property-description 'pedal-text ly-grob? "Pointer to the text of a mixed-style piano pedal.")
(grob-property-description 'penalty number? "Penalty for breaking at
this column. 10000 or more means forbid linebreak, -10000 or less
means force linebreak.  Other values influence linebreaking decisions
as a real penalty.")

(grob-property-description 'pitches list? "list of musical-pitch.")
(grob-property-description 'positions pair? "cons of staff positions (LEFT . RIGHT")
(grob-property-description 'raise number? "height for text to be raised (a negative value lowers the text.")
(grob-property-description 'ratio number? "Slur parameter.  See height-limit.")
(grob-property-description 'right-padding number? "space right of accs.")
(grob-property-description 'right-trim-amount number? "shortening of the lyric extender on the right.")
(grob-property-description 'right-widen boolean? "Whether the right edge of a piano pedal bracket should be widened by the second element of edge-widen")
(grob-property-description 'script-priority number? "A sorting key that determines in what order a script is within a stack of scripts.")
(grob-property-description 'self-alignment-X number-or-grob? "real number: -1 =
left aligned, 0 = center, 1 right-aligned in X direction.

 Set to an grob pointer, if you want that grob to be the center.
In this case, the center grob should have this object as a
reference point.

TODO: revise typing.")
(grob-property-description 'self-alignment-Y number? "like self-alignment-X but for Y axis.")
(grob-property-description 'shorten number? "the amount of space that a stem should be shortened (DOCME!)")
(grob-property-description 'shorten-pair number-pair? "the length on each side to shorten a text-spanner, for example a pedal bracket")
(grob-property-description 'common-shortest-duration moment?
                           "The most common shortest note length.
This is used in spacing. Making this larger will make the score tighter.")
(grob-property-description 'shortest-duration-space number? "Start
with this much space for the shortest duration. This is explessed in @code{spacing-increment} as unit. See also
@ref{spacing-spanner-interface}.")
(grob-property-description 'shortest-playing-duration moment? "duration of the shortest playing in that column.")
(grob-property-description 'shortest-starter-duration moment? "duration of the shortest notes that starts exactly in this column.")
(grob-property-description 'side-relative-direction dir? "if set: get the direction from a different object, and multiply by this.")
(grob-property-description 'side-support-elements grob-list? "the support, a list of grobs.")
(grob-property-description 'slope number? "some kind of slope")
(grob-property-description 'slope-limit number? "set slope to zero if slope is running away steeper than this.")
(grob-property-description 'solid boolean? "should porrectus be solidly filled?.")

(grob-property-description 'space-alist list? "Alist of break align
spacing tuples: format = (SYMBOL . (TYPE . DISTANCE)), where TYPE can be
minimum-space or extra-space.")
(grob-property-description 'space-function procedure? "return interbeam space given Beam grob and multiplicity.")
(grob-property-description 'spacing-increment number? "Add this much space for a doubled duration. Typically, the width of a note head. See also @ref{spacing-spanner-interface}.")

(grob-property-description 'spacing-wishes grob-list? "List of note spacing or staff spacing objects.")
(grob-property-description 'spacing-procedure procedure? "procedure
taking grob as argument. This is called after
before-line-breaking-callback, but before the actual line breaking
itself.  Return value is ignored.")
(grob-property-description 'stacking-dir dir? "stack contents of grobs in which direction ?.")
(grob-property-description 'staff-space number? "Amount of line leading relative to global staffspace.")
(grob-property-description 'staff-position number? "vertical position in staff spaces, counted from the middle line.")

(grob-property-description 'staffline-clearance number? "don't get closer than this to stafflines.")
(grob-property-description 'stem ly-grob? "pointer to Stem object.")
(grob-property-description 'stem-attachment-function procedure? "Where
does the stem attach to the notehead? Function takes a symbol argument
being the style. It returns a (X . Y) pair, specifying location in
terms of note head bounding box.")
(grob-property-description 'stem-end-position number? "Where does the stem end (the end is opposite to the support-head.")

(grob-property-description 'stem-shorten list? "shorten stems in forced directions given flag multiplicity:
the Nth element of the list gives the amount stem shortening of a note with N flags.
")
(grob-property-description 'stem-spacing-correction number? "optical correction amount.  [TODO: doco] ")
(grob-property-description 'stems grob-list? "list of stem objects, corresponding to the notes that the arpeggio has to be before.")
(grob-property-description 'style symbol? "a string determining what style of  glyph is typeset. Valid choices depend on the function that is reading this property. .")
(grob-property-description 'support-head ly-grob? "the note head at
one end of the stem.")
(grob-property-description 'text markup? "
Scheme markup text.  It is defined as follows:

@example
text: string | (head? text+)
head: markup | (markup+)
markup-item: property | abbrev
property: (@var{key} . @var{value})
abbrev: @code{columns lines roman music bold italic named super sub overstrike text}
        @code{finger volta timesig mmrest mark script large Large dynamic}
@end example


The following abbreviations are currently defined:
@table @samp
@item columns
 horizontal mode: set all text on one line (default)
@item lines
 vertical mode: set every text on new line
@item roman
 select roman font
@item music
 select feta font, and lookup by character name
@item bold
 select bold series
@item italic
 select italic shape
@item named
 lookup by character name
@item text
 plain text lookup (by character value)
@item super
 superscript
@item sub
 subscript
@item overstrike
 the next text or character overstrikes this one
@item finger
 select fingering number fontstyle
@item volta
 select volta number fontstyle
@item timesig
 select time signature number fontstyle
@item mmrest
 select multi measure rest number fontstyle
@item mark
 select mark number fontstyle
@item script
 select scriptsize roman fontstyle
@item large
 select large roman fontstyle
@item Large
 select Large roman fontstyle
@item dynamic
 select dynamics fontstyle
@end table
.")
(grob-property-description 'text-start boolean? "Indicator for whether a piano pedal bracket has leading text, such as Ped.")
(grob-property-description 'thick-thickness number? "thickness, measured in stafflinethickness.")
(grob-property-description 'thickness number? "thickness, measured in stafflinethickness.")
(grob-property-description 'thin-kern number? "space after a hair-line.")
(grob-property-description 'forced-distance number? "forced distance for an alignment.")

(grob-property-description 'threshold number-pair? "(cons MIN MAX), where MIN and MAX are dimensions in staffspace.")
(grob-property-description 'transparent boolean? "This is almost the
same as setting molecule-callback to #f, but this retains the
dimensions of this grob, which means that you can erase grobs
individually. .")
(grob-property-description 'bracket-visibility boolean-or-symbol? "
This controls the visibility of the tuplet bracket.
Setting it to false will prevent printing of the
bracket. Setting the property to #'if-no-beam will make it
print only if there is no beam associated with this tuplet bracket.")
(grob-property-description 'number-visibility boolean-or-symbol? "
Like @code{bracket-visibility}, but for the number.")
(grob-property-description 'tie ly-grob? "") 
(grob-property-description 'type symbol? " 

one of: line, dashed-line, trill or dotted-line.

[FIXME: type is too generic for this doc, move doco to intefrace] 
")

(grob-property-description 'break-visibility procedure? "a function that takes the break direction and returns a  cons of booleans containing (TRANSPARENT . EMPTY).


Some items need special treatment for line breaking. For example, a
clef is normally only printed at the start of a line (i.e. after a line
break).  To model this, `breakable' items (clef, key signature, bar lines,
etc.) are copied twice. Then we have three versions of each breakable
item: one version if there is no line break, one version that is printed
before the line break (at the end of a system), one version that is
printed after the line break.

Whether these versions are visible and take up space, is determined by
the outcome of the @code{break-visibility}. This grob property is a
function taking a direction (-1, 0 or 1) as argument. It returns a cons
of booleans, signifying whether this grob should be transparent and have
no extent.

")
(grob-property-description 'when moment? "when does this column happen?.")
(grob-property-description 'word-space number? "elongate left by this much (FIXME: cumbersome semantics).")
(grob-property-description 'alignment number? "alignment of lyrics on notehead, -1 is LEFT, 0 is CENTRE, 1 is RIGHT .")
(grob-property-description 'ignore-length-mismatch boolean? "if #t, stanzas with shorter lyrics can be moved away from their respective note-head by the lyric alignment code.")
(grob-property-description 'begin-alignment number? "proportion of lyric length from beginning to align with note-head for left-aligned lyrics.")
(grob-property-description 'end-alignment number? "proportion of lyric length from end to align with note-head for right-aligned lyrics.")
(grob-property-description 'width number? "width of a grob measured in staff space.")
(grob-property-description 'width-correct number? "width correction for (de)cresc. text spanners.")
(grob-property-description 'x-gap number? "horizontal gap between notehead and tie.")
(grob-property-description 'y-free number? "minimal vertical gap between slur and noteheads or stems.")
(grob-property-description 'y-offset number? "extra vertical offset for ties away from the center line.")

;;; INTERNAL

(grob-property-description 'left-neighbors grob-list? " List of
spacing-wish grobs that are close to the current column.

The closest spacing-wishes determine the actual distances between the
columns.
")
(grob-property-description 'right-neighbors grob-list? "see left-neighbors")
(grob-property-description 'left-items grob-list? "")
(grob-property-description 'right-items grob-list? "")

(grob-property-description 'cause scheme? "Any kind of causation objects (i.e. music, or perhaps translator) that was the cause for this grob.  ")
(grob-property-description 'font font-metric? "Cached font metric object")
(grob-property-description 'break-alignment-done boolean? "mark flag to signal we've done alignment already.")
(grob-property-description 'staff-symbol ly-grob? "the staff symbol grob that we're in.")
(grob-property-description 'collision-done boolean? "")
(grob-property-description 'rest ly-grob? "the staff symbol grob that we're in.")
(grob-property-description 'rest-collision ly-grob? "rest collision that a rest is in.")

(grob-property-description 'staff-support boolean? " JUNKME.")
(grob-property-description 'script-molecule pair? "index code for script.")

(grob-property-description 'accidental-grob ly-grob? "Accidental for this note.")

(grob-property-description 'causes list? "list of cause objects; these can be music objects or grobs.")
(grob-property-description 'flag-count number? "")
(grob-property-description 'chord-tremolo boolean? "if set, this beam is a tremolo. TODO: use interface for this!")
(grob-property-description 'chord pair? "?")
(grob-property-description 'begin-of-line-visible boolean? "?")

(grob-property-description 'quant-score number? "Beam quanting score
-- can be stored for debugging")
(grob-property-description 'least-squares-dy number? 
 "ideal beam slope, without damping.")
(grob-property-description 'stem-info pair? "caching of stem parameters")
(grob-property-description 'note-columns pair? "list of NoteColumn grobs.")

(grob-property-description 'if-text-padding number? "padding in case texts are there.")
(grob-property-description 'grace-space-factor number? "space grace at this fraction of the increment.")
(grob-property-description 'position-callbacks list? "list of
functions set spanner positions.")
(grob-property-description 'chord-name-function procedure? "DOCME")
(grob-property-description 'minimum-beam-collision-distance number?
"Minimum distance to beam for a rest collision.")

(grob-property-description 'avoid-note-head boolean? "if set, the stem of a chord does not pass through all note head, but start at the last note head. Used by tablature.")
(grob-property-description 'up-to-staff boolean? "if set, stems' lengths are set so as stems end out of the staff. Used by tablature.")