[XeTeX] wanted: \vadjust pre

[Vladimir Volovich]

Hi Jonathan!

xetex includes etex extensions, as well as several extensions from
pdftex (e.g. \pdfsavepos & friends). however, the following useful
extension is not implemented (the following is an excerpt from the
pdftex users manual):

  \vadjust [ pre spec ] filler { vertical mode material }

  The \vadjust implementation of pdfTEX adds an optional qualifier pre
  spec (which is the string pre) to the original TEX primitive with the
  same name. As long as there is no pre given, \vadjust behaves exactly as
  the original (see the TEXbook, p. 281); it appends an adjustment item
  created from vertical mode material to the current list after the line
  in which \vadjust appears. However with the qualifier pre, the
  adjustment item is put before the line in which \vadjust pre appears.

could you please consider adding it to xetex (and maybe some other
"general purpose extensions" mentioned in pdftex manual)?

Best,
v.