LilyPond Internals Reference: 3.2.4 align-interface

### 3.2.4 align-interface

Order grobs from top to bottom, left to right, right to left or bottom to top. For vertical alignments of staves, the `break-system-details` of the left NonMusicalPaperColumn may be set to tune vertical spacing.

#### User settable properties:

> `align-dir` (direction)

>   Which side to align? `-1`: left side, `0`: around center of width, `1`: right side.

> `axes` (list)

>   List of axis numbers. In the case of alignment grobs, this should contain only one number.

> `padding` (dimension, in staff space)

>   Add this much extra space between objects that are next to each other.

> `stacking-dir` (direction)

>   Stack objects in which direction?

#### Internal properties:

> `elements` (array of grobs)

>   An array of grobs; the type is depending on the grob where this is set in.

> `positioning-done` (boolean)

>   Used to signal that a positioning element did its job. This ensures that a positioning is only done once.

This grob interface is used in the following graphical object(s): BassFigureAlignment and VerticalAlignment.

#### Internals Reference