Disable or enable output depending on the value of num:
Disable any glyphs from being emitted to the device driver, provided
that the escape occurs at the outer level (see
\O). Motion is not suppressed so effectively
means pen up.
Enable output of glyphs, provided that the escape occurs at the outer level.
\O1 also reset the four registers ‘opminx’,
‘opminy’, ‘opmaxx’, and ‘opmaxy’ to -1.
See Register Index. These four registers mark the top left and
bottom right hand corners of a box that encompasses all written glyphs.
For example the input text:
Hello \Oworld \Othis is a test.
produces the following output:
Hello this is a test.
Provided that the escape occurs at the outer level, enable output of
glyphs and also write out to
stderr the page number and four
registers encompassing the glyphs previously written since the last call
Begin a nesting level. At start-up,
gtroff is at outer level.
The current level is contained within the read-only register
See Built-in Registers.
End a nesting level. The current level is contained within the
.O. See Built-in Registers.
This escape is
grohtml specific. Provided that this escape
occurs at the outer nesting level write the
stderr. The position of the image, P, must be specified
and must be one of
right, centered, inline). filename is associated with the
production of the next inline image.