.TH PROOF 9.1
.CT 1 writing_output
.SH NAME
proof \- troff output interpreter for 5620
.SH SYNOPSIS
.B proof
[
.BI -f fonts
]
[
.I file
]
.SH DESCRIPTION
.I Proof
reads
.IR troff (1)
intermediate language from
.I file
or standard input
and simulates the resulting pages on the screen.
If no file name is given and standard input is a terminal,
proof terminates immediately leaving a `proof layer'.
By invoking
.I proof
in a proof layer you can avoid download time.
.PP
Fonts are loaded as required.
The usual 
.IR mux (9.1)
font,
.BR defont ,
is used for unknown fonts.
Option
.B -f
preloads fonts.
Names are given relative to
.F /usr/jerq/font
and are separated by commas.
The most-used fonts are 
.LR -fR.10,I.10,B.10,S.10 .
.PP
After a layer's worth of text is displayed,
.I proof
pauses for a command from keyboard or mouse button 3.
The typed versions of commands are:
.TP \w'newline\ 'u
newline
Go on to next portion of text.
(Button 3 equivalent: 
.LR more .)
.TP
.B q
Quit, leaving a proof layer.
.TP
.B x
Exit and restart the regular terminal program.
(Equivalent to 
.L q
followed by
.LR "term mux" ;
see
.IR term (9.1)).
.TP
.BI p n
Print page
.I n.
An out-of-bounds page number means the end nearer to that number;
a missing number means page 0;
a signed number means an offset to the current page.
.PP
Button 1 gets a scroll box, which represents a full page of text.
An interior rectangle shows what part of the page is now visible.
The interior rectangle moves with the mouse, causing the layer to
scroll both vertically and horizontally.
Button 2 gets a speedometer.
The bar of the speedometer moves with the mouse
to control the rate at which new information is displayed.
.SH EXAMPLES
.TP
.L
troff -ms memo | proof
Format a memo and display it.
.TP
.L
(eqn memo | troff -ms) 2>diags | proof
Display a memo with equations.
Avoid sending diagnostics to the screen; see
.SM BUGS.
.SH FILES
.TF /usr/jerq/font/.missing
.TP
.F /usr/jerq/font/*
fonts
.TP
.F /usr/jerq/font/.missing
list of referenced but unconverted fonts
.SH SEE ALSO
.IR lp (1), 
.IR font (6),
.IR reader (9.7),
.IR psi (9.1)
.br
Brian W. Kernighan,
.I A Typesetter-independent Troff
.SH BUGS
.I Proof
breaks if other messages are directed to its layer.
In particular, unredirected
.I troff 
diagnostics will break the pipeline
.LR "troff | proof" .
.br
Windowing can get confused if the
.I troff
output is not approximately
sorted in ascending
.IR y -order.
.br
A proof layer imitates
.LR "term 33" ,
not
.IR mux .
Among other difficulties, it will not be reusable if downloaded
across the network.