Info Catalog groff: Page Layout groff: gtroff Reference groff: Fonts and Symbols

groff: Page Control

 
 5.16 Page Control
 =================
 
  -- Request: .bp [page]
  -- Request: .bp +page
  -- Request: .bp -page
  -- Register: \n[%]
      Stop processing the current page and move to the next page.  This
      request causes a break.  It can also take an argument to set
      (increase, decrease) the page number of the next page (which
      actually becomes the current page after 'bp' has finished).  The
      difference between 'bp' and 'pn' is that 'pn' does not cause a
      break or actually eject a page.  Page Layout.
 
           .de newpage                         \" define macro
           'bp                                 \" begin page
           'sp .5i                             \" vertical space
           .tl 'left top'center top'right top' \" title
           'sp .3i                             \" vertical space
           ..                                  \" end macro
 
      'bp' has no effect if not called within the top-level diversion
      (Diversions).
 
      The read-write register '%' holds the current page number.
 
      The number register '.pe' is set to 1 while 'bp' is active.  
      Page Location Traps.
 
  -- Request: .ne [space]
      It is often necessary to force a certain amount of space before a
      new page occurs.  This is most useful to make sure that there is
      not a single "orphan" line left at the bottom of a page.  The 'ne'
      request ensures that there is a certain distance, specified by the
      first argument, before the next page is triggered (see 
      Traps, for further information).  The default scaling indicator
      for 'ne' is 'v'; the default value of SPACE is 1v if no argument is
      given.
 
      For example, to make sure that no fewer than 2 lines get orphaned,
      do the following before each paragraph:
 
           .ne 2
           text text text
 
      'ne' then automatically causes a page break if there is space for
      one line only.
 
  -- Request: .sv [space]
  -- Request: .os
      'sv' is similar to the 'ne' request; it reserves the specified
      amount of vertical space.  If the desired amount of space exists
      before the next trap (or the bottom page boundary if no trap is
      set), the space is output immediately (ignoring a partially filled
      line, which stays untouched).  If there is not enough space, it is
      stored for later output via the 'os' request.  The default value
      is 1v if no argument is given; the default scaling indicator is
      'v'.
 
      Both 'sv' and 'os' ignore no-space mode.  While the 'sv' request
      allows negative values for SPACE, 'os' ignores them.
 
  -- Register: \n[nl]
      This register contains the current vertical position.  If the
      vertical position is zero and the top of page transition hasn't
      happened yet, 'nl' is set to negative value.  'gtroff' itself does
      this at the very beginning of a document before anything has been
      printed, but the main usage is to plant a header trap on a page if
      this page has already started.
 
      Consider the following:
 
           .de xxx
           .  sp
           .  tl ''Header''
           .  sp
           ..
           .
           First page.
           .bp
           .wh 0 xxx
           .nr nl (-1)
           Second page.
 
      Result:
 
           First page.
 
           ...
 
                                        Header
 
           Second page.
 
           ...
 
      Without resetting 'nl' to a negative value, the just planted trap
      would be active beginning with the _next_ page, not the current
      one.
 
      Diversions, for a comparison with the '.h' and '.d'
      registers.
 

Info Catalog groff: Page Layout groff: gtroff Reference groff: Fonts and Symbols