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NonMusicalPaperColumn
NonMusicalPaperColumn grobs are created by: Score_engraver
Grobs can be distinguished in their role in the horizontal spacing.
Many grobs define constraints on the spacing by their sizes. For
example, note heads, clefs, stems, and all other symbols with a fixed
shape. These grobs form a subtype called Item .
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 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.
Default value: (unset)
breakable (boolean)
- boolean indicating if this is a breakable item (clef, barline, key sig, etc.).
Default value: (unset)
no-spacing-rods (boolean)
- read from grobs: boolean that makes Separation_item ignore this item (MOVE ME TO ITEM).
Default value: (unset)
A grob (a Paper_column) that takes part in the
spacing problem.
ideal-distances (list)
- (OBJ . (DIST . STRENGTH)) pairs.
Default value: (unset)
left-neighbors (list of grobs)
- List of
spacing-wish grobs that are close to the current column.
The closest spacing-wishes determine the actual distances between the
columns.
Default value: (unset)
measure-length (moment)
- Length of a
measure. Used in some spacing situations.
Default value: (unset)
minimum-distances (list)
- list of rods (ie. (OBJ . DIST) pairs).
Default value: (unset)
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.
Default value: (unset)
right-neighbors (list of grobs)
- see left-neighbors
Default value: (unset)
spacing-wishes (list of grobs)
- List of note spacing or staff spacing objects.
Default value: (unset)
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)
Paper_columns form the top-most item parent. (The Paper_columns X
parent is System, which is a spanner.)
Paper_columns form the units for the spacing engine. They are
numbered, the first (leftmost) is column 0. Numbering happens before
line-breaking, and columns are not renumbered after line breaking.
Since many columns go unused, you should only use the rank field to
get ordering information. Two adjacent columns may have
non-adjacent numbers.
Don't be confused by right-items: each spacing wish can also contain
a number of items, with which a spacing constraint may be kept. It's
a little baroque, but it might come in handy later on?
between-cols (pair)
- Where to attach a loose column to
Default value: (unset)
between-system-string (string)
- string
to dump between two systems. Useful for forcing pagebreaks.
Default value: (unset)
bounded-by-me (list of grobs)
- list of spanners that have this
column as start/begin point. Only columns that have grobs or act as bounds are spaced.
Default value: (unset)
shortest-playing-duration (moment)
- duration of the shortest playing in that column.
Default value: (unset)
shortest-starter-duration (moment)
- duration of the shortest notes that starts exactly in this column.
Default value: (unset)
when (moment)
- when does this column happen?.
Default value: (unset)
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: (unset)
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:
Paper_column::before_line_breaking
cause (any type)
- Any kind of causation objects (i.e. music, or perhaps translator) that was the cause for this grob.
Default value: (unset)
causes (list)
- list of cause objects; these can be music objects or grobs.
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 . NonMusicalPaperColumn) (interfaces grob-interface paper-column-interface axis-group-interface spaceable-grob-interface item-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)
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