\O[
num]
¶Suppress GNU troff
output of glyphs and geometric primitives.
The sequences \O2
, \O3
, \O4
, and \O5
are
intended for internal use by grohtml
.
Disable the emission of glyphs and geometric primitives to the output
driver, provided that this sequence occurs at the outermost level
(see \O3
and \04
below). Horizontal motions corresponding
to non-overstruck glyph widths still occur.
Enable the emission of glyphs and geometric primitives to the output driver, provided that this sequence occurs at the outermost level.
\O0
and \O1
also reset the four registers opminx
,
opminy
, opmaxx
, and opmaxy
to −1. These
four registers mark the top left and bottom right hand corners of a box
encompassing all written glyphs.
Provided that this sequence occurs at the outermost level, enable
emission of glyphs and geometric primitives, and write to the standard
error stream the page number and values of the four aforementioned
registers encompassing glyphs written since the last interpolation of a
\O
sequence, as well as the page offset, line length, image file
name (if any), horizontal and vertical device motion quanta, and input
file name. Numeric values are in basic units.
Begin a nesting level. This is an internal mechanism for grohtml
while producing images. At startup, gtroff
is at the outermost
level. These sequences are generated when processing the source
document with pre-grohtml
, which uses gtroff
with
the ps
output device, Ghostscript, and the PNM tools to produce
images in PNG format. They start a new page if the device is not
html
or xhtml
, to reduce the possibility of images
crossing a page boundary.
End a nesting level.
Provided that this sequence occurs at the outermost level, write the
name file
to the standard error stream at position P, which
must be one of l
, r
, c
, or i
,
corresponding to left, right, centered, and inline alignments within the
document, respectively. file is a name associated with the
production of the next image.
\n[.O]
¶Output suppression nesting level applied by \O3
and \O4
escape sequences.