Automatic setting of frame's Y params

[uliska]

So far the Y value of frames has to be passed explicitly.

It would be good if this could (try to) detect the extent of what is actually included in the music and determine the values accordingly.

[KlausBlum]

David Nalesnik once wrote a box engraver that calculates its Y extent from a given music expression:
http://lilypond.1069038.n5.nabble.com/box-around-notes-td35581.html

User-specified Y values can also be a valuable feature, especially if you want different Y extents for the left and right border.
IMO both approaches are worth being continued.