File: groff.info,  Node: Artificial Fonts,  Next: Ligatures and Kerning,  Prev: Special Fonts,  Up: Using Fonts

5.19.7 Artificial Fonts
-----------------------

There are a number of requests and escape sequences for artificially
creating fonts.  These are largely vestiges of the days when output
devices did not have a wide variety of fonts, and when 'nroff' and
'troff' were separate programs.  Most of them are no longer necessary in
GNU 'troff'.  Nevertheless, they are supported.

 -- Escape sequence: \H'height'
 -- Escape sequence: \H'+height'
 -- Escape sequence: \H'-height'
 -- Register: \n[.height]
     Change (increment, decrement) the height of the current font, but
     not the width.  If HEIGHT is zero, restore the original height.
     Default scaling unit is 'z'.

     The read-only register '.height' contains the font height as set by
     '\H'.

     Currently, only the '-Tps' and '-Tpdf' devices support this
     feature.

     '\H' doesn't produce an input token in GNU 'troff'.  As a
     consequence, it can be used in requests like 'mc' (which expects a
     single character as an argument) to change the font on the fly:

          .mc \H'+5z'x\H'0'

     In compatibility mode, 'gtroff' behaves differently: If an
     increment or decrement is used, it is always taken relative to the
     current type size and not relative to the previously selected font
     height.  Thus,

          .cp 1
          \H'+5'test \H'+5'test

     prints the word 'test' twice with the same font height (five points
     larger than the current font size).

 -- Escape sequence: \S'slant'
 -- Register: \n[.slant]
     Slant the current font by SLANT degrees.  Positive values slant to
     the right.  Only integer values are possible.

     The read-only register '.slant' contains the font slant as set by
     '\S'.

     Currently, only the '-Tps' and '-Tpdf' devices support this
     feature.

     '\S' doesn't produce an input token in GNU 'troff'.  As a
     consequence, it can be used in requests like 'mc' (which expects a
     single character as an argument) to change the font on the fly:

          .mc \S'20'x\S'0'

     This escape is incorrectly documented in the AT&T 'troff' manual;
     the slant is always set to an absolute value.

 -- Request: .ul [lines]
     The 'ul' request normally underlines subsequent lines if a TTY
     output device is used.  Otherwise, the lines are printed in italics
     (only the term 'underlined' is used in the following).  The single
     argument is the quantity of input lines to be underlined; with no
     argument, the next line is underlined.  If LINES is zero or
     negative, stop the effects of 'ul' (if it was active).  Requests
     and empty lines do not count for computing the number of underlined
     input lines, even if they produce some output like 'tl'.  Lines
     inserted by macros (e.g., invoked by a trap) do count.

     At the beginning of 'ul', the current font is stored and the
     underline font is activated.  Within the span of a 'ul' request, it
     is possible to change fonts, but after the last line affected by
     'ul' the saved font is restored.

     This number of lines still to be underlined is associated with the
     environment (*note Environments::).  The underline font can be
     changed with the 'uf' request.

     The 'ul' request does not underline spaces.

 -- Request: .cu [lines]
     The 'cu' request is similar to 'ul' but underlines spaces as well
     (if a TTY output device is used).

 -- Request: .uf font
     Set the underline font (globally) used by 'ul' and 'cu'.  By
     default, this is the font at position 2.  FONT can be either a
     non-negative font position or the name of a font.

 -- Request: .bd font [offset]
 -- Request: .bd font1 font2 [offset]
 -- Register: \n[.b]
     Embolden FONT by overstriking its glyphs offset by OFFSET units
     minus one.

     Two syntax forms are available.

        * Imitate a bold font unconditionally.  The first argument
          specifies the font to embolden, and the second is the number
          of basic units, minus one, by which the two glyphs are offset.
          If the second argument is missing, emboldening is turned off.

          FONT can be either a non-negative font position or the name of
          a font.

          OFFSET is available in the '.b' read-only register if a
          special font is active; in the 'bd' request, its default unit
          is 'u'.

        * Imitate a bold form conditionally.  Embolden FONT1 by OFFSET
          only if font FONT2 is the current font.  This request can be
          issued repeatedly to set up different emboldening values for
          different current fonts.  If the second argument is missing,
          emboldening is turned off for this particular current font.

          This affects special fonts only (either set up with the
          'special' command in font files or with the 'fspecial'
          request).

 -- Request: .cs font [width [em-size]]
     Switch to and from "constant glyph space mode".  If activated, the
     width of every glyph is WIDTH/36 ems.  The em size is given
     absolutely by EM-SIZE; if this argument is missing, the em value is
     taken from the current font size (as set with the 'ps' request)
     when the font is effectively in use.  Without second and third
     argument, constant glyph space mode is deactivated.

     Default scaling unit for EM-SIZE is 'z'; WIDTH is an integer.