GNU LilyPond

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item-interface

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)

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Copyright (c) 1997--2002 Han-Wen Nienhuys and Jan Nieuwenhuizen.

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