Re: Add and use note-collision-threshold grob property (issue 271680043 by address@hidden)

[paulwmorris]

Please review, thanks.

When StaffSymbol.staff-space is overridden to a value less than 1,
collisions can occur between simultaneous notes that are more than one
staff space apart.

This patch introduces a property "note-collision-threshold" that makes
it possible to prevent this.  By setting this property to 2 or more,
LilyPond will identify notes 2 or more staff positions apart as
collisions and move the notes accordingly to prevent them.

Basically, this patch un-hard-codes the assumption that collisions only
occur when simultaneous notes are 1 staff space apart and allows the
user to override this threshold with a different value when that is
needed.

See regtest for an example of use.

-Paul

https://codereview.appspot.com/271680043/