### 3.2.117 system-interface

This is the top-level object: Each object in a score ultimately has a `System` object as its X and Y parent.

#### User settable properties:

> `labels` (list)

>   List of labels (symbols) placed on a column.

#### Internal properties:

> `all-elements` (array of grobs)

>   An array of all grobs in this line. Its function is to protect objects from being garbage collected.

> `columns` (array of grobs)

>   An array of grobs, typically containing `PaperColumn` or `NoteColumn` objects.

> `footnote-stencil` (stencil)

>   The stencil of a system’s footnotes.

> `footnotes-before-line-breaking` (array of grobs)

>   Footnote grobs of a whole system.

> `footnotes-after-line-breaking` (array of grobs)

>   Footnote grobs of a broken system.

> `in-note-direction` (direction)

>   Direction to place in-notes above a system.

> `in-note-padding` (number)

>   Padding between in-notes.

> `in-note-stencil` (stencil)

>   The stencil of a system’s in-notes.

> `pure-Y-extent` (pair of numbers)

>   The estimated height of a system.

> `vertical-alignment` (graphical (layout) object)

>   The VerticalAlignment in a System.

This grob interface is used in the following graphical object(s): System.

#### Internals Reference v2.18.2 (稳定分支).