Some days ago I wrote:
> Consider this snippet.
>
> ```tex
> cancellationFirst =
> \override Score.BreakAlignment.break-align-orders =
> #(grob-transformer 'break-align-orders
> (lambda (grob orig)
> (let ((vec (vector-copy orig))
> (middle '(key-cancellation
> staff-bar
> key-signature)))
> (vector-set! vec 1 middle)
> vec)))
>
> music = { \key ces \major ces'1 \bar "||"
> \key cis \major cis'1 }
>
> { <>^\markup "default"
> \music }
>
> { <>^\markup "cancellationFirst"
> \cancellationFirst
> \music }
> ```
>
> As can be seen in the image, flipping the order of the bar line and
> the key cancellation changes the horizontal spacing between the
> `NoteHead` and `NonMusicalPaperColumn` grobs in a bad way. Why does
> this happen, and how can I avoid this?
>
> The third line shows the same without a bar line, where the spacing
> is just fine.
Any takers? If nobody knows the reason, how can I debug this most
easily to find the culprit?
Werner
