5.15 Page Layout

gtroff provides some very primitive operations for controlling page layout.

Request: .pl [length]

Request: .pl +length

Request: .pl -length

Register: \n[.p]

Set the page length to length (or increment or decrement the current value by length). This is the length of the physical output page. The default scaling indicator is ‘v’.

The current setting can be found in the read-only number register ‘.p’.

Note that this only specifies the size of the page, not the top and bottom margins. Those are not set by gtroff directly. See Traps, for further information on how to do this.

Negative pl values are possible also, but not very useful: No trap is sprung, and each line is output on a single page (thus suppressing all vertical spacing).

If no argument or an invalid argument is given, pl sets the page length to 11i.

gtroff provides several operations that help in setting up top and bottom titles (or headers and footers).

Request: .tl 'left'center'right'

Print a title line. It consists of three parts: a left justified portion, a centered portion, and a right justified portion. The argument separator ‘'’ can be replaced with any character not occurring in the title line. The ‘%’ character is replaced with the current page number. This character can be changed with the pc request (see below).

Without argument, tl is ignored.

Some notes:

• The line length set by the ll request is not honoured by tl; use the lt request (described below) instead, to control line length for text set by tl.
• A title line is not restricted to the top or bottom of a page.
• tl prints the title line immediately, ignoring a partially filled line (which stays untouched).
• It is not an error to omit closing delimiters. For example, ‘.tl /foo’ is equivalent to ‘.tl /foo///’: It prints a title line with the left justified word ‘foo’; the centered and right justfied parts are empty.
• tl accepts the same parameter delimiting characters as the \A escape; see Escapes.

Request: .lt [length]

Request: .lt +length

Request: .lt -length

Register: \n[.lt]

The title line is printed using its own line length, which is specified (or incremented or decremented) with the lt request. Initially, the title line length is set to 6.5i. If a negative line length is specified (which is not allowed), gtroff emits a warning of type ‘range’ and sets the title line length to zero. The default scaling indicator is ‘m’. If lt is called without an argument, the title length is reset to the previous value before the last call to lt.

The current setting of this is available in the .lt read-only number register; it is associated with the current environment (see Environments).

Request: .pn page

Request: .pn +page

Request: .pn -page

Register: \n[.pn]

Change (increase or decrease) the page number of the next page. The only argument is the page number; the request is ignored without a parameter.

The read-only number register .pn contains the number of the next page: either the value set by a pn request, or the number of the current page plus 1.

Request: .pc [char]

Change the page number character (used by the tl request) to a different character. With no argument, this mechanism is disabled. Note that this doesn’t affect the number register %.

See Traps.