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System

System grobs are created by: Score_engraver

spanner-interface

Other grobs have a shape that depends on the horizontal spacing. For example, slur, beam, tie, etc. These grobs form a subtype called Spanner. All spanners have two span-points (these must be Items), one on the left and one on the right. The left bound is also the X-reference point of the spanner.


minimum-length (dimension, in staff space)
try to make the Grob at least this long.

Also works as a scaling parameter for the length of hyphen. . Default value: (unset)

axis-group-interface

a group of coupled grobs


axes (list)
list of axis numbers. In the case of alignment grobs, this should contain only one number. Default value: '(0 1)

system-interface

Super grob, parent of all:

The columns of a score that form one line. The toplevel grob. Any grob has a Line_of_score as both X and Y reference point. The Paper_score contains one grob of this type. Control enters the Grob dependency calculation from this single Line_of_score object.


all-elements (list of grobs)
list of all grobs in this line. Needed for protecting grobs from GC. Default value: (unset)
between-system-string (string)
string to dump between two systems. Useful for forcing pagebreaks. Default value: (unset)
columns (list of grobs)
list of grobs, typically containing paper-columns. Default value: (unset)

grob-interface

In music notation, lots of symbols are related in some way. You can think of music notation as a graph where nodes are formed by the symbols, and the arcs by their relations. A grob is a node in that graph. The directed edges in the graph are formed by references to other grobs (i.e. pointers). This big graph of grobs specifies the notation problem. The solution of this problem is a description of the printout in closed form, i.e. a list of values. These values are Molecules.

All grobs have an X and Y-position on the page. These X and Y positions are stored in a relative format, so they can easily be combined by stacking them, hanging one grob to the side of another, and coupling them into a grouping-grob.

Each grob has a reference point (a.k.a. parent): the position of a grob is stored relative to that reference point. For example the X-reference point of a staccato dot usually is the note head that it applies to. When the note head is moved, the staccato dot moves along automatically.

A grob is often associated with a symbol, but some grobs do not print any symbols. They take care of grouping objects. For example, there is a separate grob that stacks staves vertically. The NoteCollision is also an abstract grob: it only moves around chords, but doesn't print anything.


X-extent (pair of numbers)
Store extent. internal use only. Default value: (unset)
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 X-extent-callback and Y-extent-callback. There can be only one extent-callback for each axis. No callback (Scheme value #f) means: `empty in this direction'. If you fill in a pair of numbers, that pair hard-codes the extent in that coordinate.

Default value: Axis_group_interface::group_extent_callback

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.

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

The callbacks will be executed in the order 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.

Default value: (unset)

Y-extent (pair of numbers)
Store extent. internal use only. Default value: (unset)
Y-extent-callback (procedure)
see X-extent-callback. Default value: Axis_group_interface::group_extent_callback
Y-offset-callbacks (list)
see X-offset-callbacks. Default value: (unset)
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. Default value: (unset)
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. Default value: (unset)
cause (any type)
Any kind of causation objects (i.e. music, or perhaps translator) that was the cause for this grob. Default value: (unset)
dependencies (list of grobs)
list of score-grob pointers that indicate who to compute first for certain global passes. Default value: (unset)
extra-X-extent (pair of numbers)
enlarge in X dimension by this much, measured in staff space. Default value: (unset)
extra-Y-extent (pair of numbers)
see extra-Y-extent. Default value: (unset)
extra-offset (pair of numbers)
pair of reals (a cons) forcing an extra offset before outputting. extra-offset is added just before `printing' the grob, so the typesetting engine is completely oblivious to it.

Default value: (unset)

interfaces (list)
list of symbols indicating the interfaces supported by this object. Is initialized from the meta field. Default value: (unset)
layer (number)
The output layer [0..2]. The default is 1. Default value: (unset)
meta (list)
Alist of meta information of this grob.

The alist contains the following entries: name, interfaces.

Default value: '((name . System) (interfaces grob-interface system-interface axis-group-interface spanner-interface))

minimum-X-extent (pair of numbers)
minimum size in X dimension, measured in staff space. Default value: (unset)
minimum-Y-extent (pair of numbers)
see minimum-Y-extent. Default value: (unset)
molecule (unknown)
Cached output of the molecule-callback. Default value: (unset)
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 input/regression/molecule-hacking.ly.

Default value: (unset)

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. Default value: (unset)
staff-symbol (grob (GRaphical OBject))
the staff symbol grob that we're in. Default value: (unset)
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. . Default value: (unset)

This page is for LilyPond-2.0.1 (stable-branch).

Report errors to <bug-lilypond@gnu.org>.