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Custos

Custos grobs are created by: Custos_engraver

break-aligned-interface

Items that are aligned in prefatory matter

break-align-symbol (symbol):

the index in the spacing table (symbol) of the to be aligned item. Default value: 'Custos

visibility-lambda (procedure):

a function that takes the break direction and returns a cons of booleans containing (TRANSPARENT . EMPTY). Default value: #<procedure end-of-line-visible (d)>

breakable (boolean):

boolean indicating if this is a breakable item (clef, barline, key sig, etc.). Default value: #t

staff-symbol-referencer-interface

Object whose Y position is meaning with reference to a staff symbol. Objects that have this interface should include Staff_symbol_referencer::callback in their Y-offset-callback.

staff-symbol (boolean):

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

staff-position (number):

vertical position in staff spaces, counted from the middle line. Default value: (unset)

custos-interface

A custos is a staff context symbol that appears at the end of a staff line with monophonic musical contents (i.e. with a single voice). It anticipates the pitch of the first note of the following line and thus helps the player or singer to manage line breaks during performance, thus enhancing readability of a score.

Custodes were frequently used in music notation until the 16th century. There were different appearences for different notation styles. Nowadays, they have survived only in special forms of musical notation such as via the editio vaticana dating back to the beginning of the 20th century.

[TODO: add to glossary]

style (symbol):

a string determining what style of glyph is typeset. Valid choices depend on the function that is reading this property. . Default value: 'vaticana

general-grob-interface

All grobs support this

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. Default value: (unset)

Y-offset-callbacks (list):

see X-offset-callbacks. Default value: '(#<primitive-procedure Staff_symbol_referencer::callback>)

X-extent-callback (procedure):

procedure taking an grob and axis argument, returning a number-pair. The return value is the extent of the grob. Default value: (unset)

Y-extent-callback (procedure):

see X-extent-callback. Default value: (unset)

molecule-callback (procedure):

Function taking grob as argument, returning a Scheme encoded Molecule. Default value: #<primitive-procedure Custos::brew_molecule>

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. 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)

dependencies (list):

list of score-grob pointers that indicate who to compute first for certain global passes. 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)

extra-extent-X (pair of numbers):

enlarge in X dimension by this much, measured in staff space. Default value: (unset)

extra-extent-Y (pair of numbers):

see extra-extent-Y. Default value: (unset)

minimum-extent-X (pair of numbers):

minimum size in X dimension, measured in staff space. Default value: (unset)

minimum-extent-Y (pair of numbers):

see minimum-extent-Y. Default value: (unset)

origin (input location):

location in input file of the definition. 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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Copyright (c) 1997--2001 Han-Wen Nienhuys and Jan Nieuwenhuizen.

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