Vertical spacing: over-estimation of markups height

[Nicolas Sceaux]

Hi,

Page spacing algorithm seems to over estimate the height of markup lines.

Example:

===========
\version "2.13.23"
\header { tagline = ##f }
\paper {
  annotate-spacing = ##t
  #(define page-breaking ly:minimal-breaking)
}
#(set-default-paper-size "a6" 'portrait)

#(define-markup-list-command (test layout props num) (number?)
   (interpret-markup-list layout props
                          (let ((result '()))
                            (do ((i 0 (1+ i)))
                                ((> i num) (reverse! result))
                              (set! result (cons (format "~a" i) result))))))

\markuplines \column-lines \test #50
===========

The page spacing code gives:

New page
  add line with estimated full height=3.000000 --> estimated space left: 
76.374882
  add line with estimated tallness=3.000000 --> estimated space left: 72.874882
  add line with estimated tallness=3.000000 --> estimated space left: 69.374882
  add line with estimated tallness=3.000000 --> estimated space left: 65.874882
  add line with estimated tallness=3.000000 --> estimated space left: 62.374882
  add line with estimated tallness=3.000000 --> estimated space left: 58.874882
  add line with estimated tallness=3.000000 --> estimated space left: 55.374882
  add line with estimated tallness=3.000000 --> estimated space left: 51.874882
  add line with estimated tallness=3.000000 --> estimated space left: 48.374882
  add line with estimated tallness=3.000000 --> estimated space left: 44.874882
  add line with estimated tallness=3.000000 --> estimated space left: 41.374882
  add line with estimated tallness=3.000000 --> estimated space left: 37.874882
  add line with estimated tallness=3.000000 --> estimated space left: 34.374882
  add line with estimated tallness=3.000000 --> estimated space left: 30.874882
  add line with estimated tallness=3.000000 --> estimated space left: 27.374882
  add line with estimated tallness=3.000000 --> estimated space left: 23.874882
  add line with estimated tallness=3.000000 --> estimated space left: 20.374882
  add line with estimated tallness=3.000000 --> estimated space left: 16.874882
  add line with estimated tallness=3.000000 --> estimated space left: 13.374882
  add line with estimated tallness=3.000000 --> estimated space left: 9.874882
  add line with estimated tallness=3.000000 --> estimated space left: 6.374882
  add line with estimated tallness=3.000000 --> estimated space left: 2.874882
  add line with estimated tallness=3.000000 --> estimated space left: -0.625118 
(=> put this line on a new page)
New page
  add line with estimated full height=3.000000 --> estimated space left: 
74.304290
  add line with estimated tallness=3.000000 --> estimated space left: 70.804290
  add line with estimated tallness=3.000000 --> estimated space left: 67.304290
  add line with estimated tallness=3.000000 --> estimated space left: 63.804290
  add line with estimated tallness=3.000000 --> estimated space left: 60.304290
  add line with estimated tallness=3.000000 --> estimated space left: 56.804290
  add line with estimated tallness=3.000000 --> estimated space left: 53.304290
  add line with estimated tallness=3.000000 --> estimated space left: 49.804290
  add line with estimated tallness=3.000000 --> estimated space left: 46.304290
  add line with estimated tallness=3.000000 --> estimated space left: 42.804290
  add line with estimated tallness=3.000000 --> estimated space left: 39.304290
  add line with estimated tallness=3.000000 --> estimated space left: 35.804290
  add line with estimated tallness=3.000000 --> estimated space left: 32.304290
  add line with estimated tallness=3.000000 --> estimated space left: 28.804290
  add line with estimated tallness=3.000000 --> estimated space left: 25.304290
  add line with estimated tallness=3.000000 --> estimated space left: 21.804290
  add line with estimated tallness=3.000000 --> estimated space left: 18.304290
  add line with estimated tallness=3.000000 --> estimated space left: 14.804290
  add line with estimated tallness=3.000000 --> estimated space left: 11.304290
  add line with estimated tallness=3.000000 --> estimated space left: 7.804290
  add line with estimated tallness=3.000000 --> estimated space left: 4.304290
  add line with estimated tallness=3.000000 --> estimated space left: 0.804290
  add line with estimated tallness=3.000000 --> estimated space left: -2.695710 
(=> put this line on a new page)
New page
  add line with estimated full height=3.000000 --> estimated space left: 
74.270146
  add line with estimated tallness=3.000000 --> estimated space left: 70.770146
  add line with estimated tallness=3.000000 --> estimated space left: 67.270146
  add line with estimated tallness=3.000000 --> estimated space left: 63.770146
  add line with estimated tallness=3.000000 --> estimated space left: 60.270146
  add line with estimated tallness=3.000000 --> estimated space left: 56.770146
  add line with estimated tallness=3.000000 --> estimated space left: 53.270146


However, once the lines areactually printed on page, the space left on each page
is 14.38, 13.81 and 58.77.

As a result, a gap is observed at the bottom of the first pages, where more 
text line
could have been placed.

Nicolas