headers and footers with new vertical layout engine

[Werner LEMBERG]

[git b6e82e5a from today]


Joe,


since documentation of your changes is not yet available, I have to
ask directly: What's the new method for providing proper distances
between the header, the body, and the footer of a page?  If I do it
the old way (this is, I just run a new lilypond binary on my score)
the footer line gets always attached to the body without any vertical
space inbetween, and for page numbers it sometimes even happens that
stuff from the first staff is positioned above it...[1]

Do I now have to provide a strut within the footer or header line to
signal the correct vertical extent?


    Werner


[1] This might be related to my special setup of using an invisible,
    hand-made `top' context which holds tempo indications, marks, and
    meter changes, and which gets included in the full score and all
    parts:

      \score {
        \context Top = "top" {
          \override VerticalAxisGroup
                      #'minimum-Y-extent = #'(0 . 0)
          \override VerticalAxisGroup
                      #'staff-affinity = #DOWN
          \override VerticalAxisGroup
                      #'inter-staff-spacing = #'((padding . 1))
          <other layout properties>

          ...
        }

        <other instruments>


        \layout {
          \context {
            \name "Top"
            \alias "Staff"
            \type "Engraver_group"
            \consists "Output_property_engraver"
            \consists "Text_spanner_engraver"
            \consists "Bar_engraver"
            \consists "Font_size_engraver"
            \consists "Skip_event_swallow_translator"
            \consists "Script_engraver"
            \consists "Text_engraver"
            \consists "Axis_group_engraver"

            \override VerticalAxisGroup #'Y-extent = ##f
            \override BarLine #'transparent = ##t
          }
          ...
        }
      }

    I'm inclined to think that this is a bug -- if two items from an
    upper and lower staff or header line have (almost) the same
    horizontal position, the layout engine must not invert the
    vertical position of the grobs (see attached image; `110' is a bar
    number, `10' is a page number, and `14' a rehearsal number).