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4.4.3 Vertical collision avoidance

Intuitively, there are some objects in musical notation that belong to the staff and there are other objects that should be placed outside the staff. Objects belonging outside the staff include things such as rehearsal marks, text and dynamic markings (from now on, these will be called outside-staff objects). LilyPond’s rule for the vertical placement of outside-staff objects is to place them as close to the staff as possible but not so close that they collide with another object.

LilyPond uses the outside-staff-priority property to determine whether a grob is an outside-staff object: if outside-staff-priority is a number, the grob is an outside-staff object. In addition, outside-staff-priority tells LilyPond in which order the objects should be placed.

First, LilyPond places all the objects that do not belong outside the staff. Then it sorts the outside-staff objects according to their outside-staff-priority (in increasing order). One by one, LilyPond takes the outside-staff objects and places them so that they do not collide with any objects that have already been placed. That is, if two outside-staff grobs are competing for the same space, the one with the lower outside-staff-priority will be placed closer to the staff.

A listing of defaults for outside-staff-priority may be found in Default values for outside-staff-priority.

\relative c'' {
  c4_"Text"\pp
  r2.
  \once \override TextScript.outside-staff-priority = 1
  c4_"Text"\pp % this time the text will be closer to the staff
  r2.
  % by setting outside-staff-priority to a non-number,
  % we disable the automatic collision avoidance
  \once \override TextScript.outside-staff-priority = ##f
  \once \override DynamicLineSpanner.outside-staff-priority = ##f
  c4_"Text"\pp % now they will collide
}

The vertical padding around outside-staff objects can be controlled with property outside-staff-padding.

\relative {
  \once \override TextScript.outside-staff-padding = 0
  a'4-"outside-staff-padding = 0"
  \once \override TextScript.outside-staff-padding = 3
  d-"outside-staff-padding = 3"
  c-"default outside-staff-padding"
  b-"default outside-staff-padding"
  R1
}

By default, outside-staff objects are placed so they avoid a horizontal collision with previously-positioned grobs. This can lead to situations in which objects are placed close to each other horizontally. As shown in the example below, setting outside-staff-horizontal-padding increases the horizontal spacing required, and in this case moves the text up to prevent it from getting too close to the ledger lines.

\relative {
  c''4^"Word" c c''2
  R1
  \once \override TextScript.outside-staff-horizontal-padding = 1
  c,,4^"Word" c c''2
}

See also

Snippets: Spacing.