Overview of object-specific horizontal spacing tweaks
Layout objects that have a horizontally fixed position are called
items (as opposed to spanners) and, for the purpose
of horizontal spacing, are grouped into columns. Note
heads and rests, forming the main musical material, together with
those objects that are logically linked to them – accidentals,
articulations, stems, dots, etc. – are all part of ‘musical
columns’ (represented by NoteColumn
grobs). Prefatory
matter, such as clefs, time signatures and bar lines, is grouped
into ‘non-musical columns’ (represented by
NonMusicalPaperColumn
grobs). In the following example,
musical items are colored red, while non-musical items are blue.
This example shows that there is an alternation between musical and non-musical columns. The first non-musical column contains a clef and a time signature. The first musical column has a note head with its stem and articulation. The second non-musical column is empty and thus removed during the layout process. The second musical column has a note again. The third non-musical column contains a clef, a bar line and a rehearsal mark, etc.
Within one column, spacing is fixed. On the other hand, the amount of space between consecutive columns is flexible. As we shall see, the methods to adjust spacing within a column and between columns are different.