352 lines
8.7 KiB
Plaintext
352 lines
8.7 KiB
Plaintext
.\" This module is believed to contain source code proprietary to AT&T.
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.\" Use and redistribution is subject to the Berkeley Software License
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.\" Agreement and your Software Agreement with AT&T (Western Electric).
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.\"
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.\" @(#)tt06 8.1 (Berkeley) 6/8/93
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.\" Copyright (C) Caldera International Inc. 2001-2002. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions are
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.\" met:
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.\"
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.\" Redistributions of source code and documentation must retain the above
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.\" copyright notice, this list of conditions and the following
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.\" disclaimer.
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.\"
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.\" Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\"
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.\" This product includes software developed or owned by Caldera
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.\" International, Inc. Neither the name of Caldera International, Inc.
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.\" nor the names of other contributors may be used to endorse or promote
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.\" products derived from this software without specific prior written
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.\" permission.
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.\"
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.\" USE OF THE SOFTWARE PROVIDED FOR UNDER THIS LICENSE BY CALDERA
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.\" INTERNATIONAL, INC. AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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.\" DISCLAIMED. IN NO EVENT SHALL CALDERA INTERNATIONAL, INC. BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
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.\" BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
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.\" OR OTHERWISE) RISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
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.\" IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.NH
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Local Motions: Drawing lines and characters
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.PP
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Remember `Area = \(*pr\u2\d' and the big `P'
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in the Paternoster.
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How are they done?
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.UL troff
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provides a host of commands for placing characters of any size
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at any place.
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You can use them to draw special characters
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or to tune your output for a particular appearance.
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Most of these commands are straightforward, but messy to read
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and tough to type correctly.
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.PP
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If you won't use
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.UL eqn ,
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subscripts and superscripts are most easily done with
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the half-line local motions
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.BD \eu
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and
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.BD \ed .
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To go back up the page half a point-size, insert a
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.BD \eu
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at the desired place;
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to go down, insert a
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.BD \ed .
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.BD \eu \& (
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and
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.BD \ed
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should always
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be used in pairs, as explained below.)
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Thus
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.P1
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Area = \e(*pr\eu2\ed
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.P2
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produces
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.P1
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Area = \(*pr\u2\d
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.P2
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To make the `2' smaller, bracket it with
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.BD \es\-2...\es0 .
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Since
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.BD \eu
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and
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.BD \ed
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refer to the current point size,
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be sure to put them either both inside or both outside
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the size changes,
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or you will get an unbalanced vertical motion.
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.PP
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Sometimes the space given by
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.BD \eu
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and
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.BD \ed
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isn't the right amount.
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The
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.BD \ev
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command can be used to request an arbitrary amount of vertical motion.
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The in-line command
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.P1
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\ev'(amount)'
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.P2
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causes motion up or down the page by the amount specified in
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`(amount)'.
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For example, to move the `P' down, we used
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.P1 2
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.ta 1i
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^in +0.6i (move paragraph in)
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^ll \-0.3i (shorten lines)
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^ti \-0.3i (move P back)
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\ev'2'\es36P\es0\ev'\-2'ater noster qui est
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in caelis ...
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.P2
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A minus sign causes upward motion, while
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no sign or a plus sign means down the page.
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Thus
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.BD \ev\(fm\-2\(fm
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causes an upward vertical motion
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of two line spaces.
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.PP
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There are many other ways to specify the amount of motion _
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.P1
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\ev'0.1i'
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\ev'3p'
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\ev'\-0.5m'
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.P2
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and so on are all legal.
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Notice that the scale specifier
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.BD i
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or
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.BD p
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or
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.BD m
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goes inside the quotes.
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Any character can be used in place of the quotes;
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this is also true of all other
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.UL troff
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commands described in this section.
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.PP
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Since
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.UL troff
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does not take within-the-line vertical motions into account
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when figuring out where it is on the page,
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output lines can have unexpected positions
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if the left and right ends aren't at the same
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vertical position.
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Thus
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.BD \ev ,
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like
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.BD \eu
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and
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.BD \ed ,
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should always balance upward vertical motion in a line with
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the same amount in the downward direction.
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.PP
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Arbitrary horizontal motions are also available _
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.BD \eh
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is quite analogous to
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.BD \ev ,
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except that the default scale factor is ems instead of line spaces.
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As an example,
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.P1
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\eh'\-0.1i'
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.P2
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causes a backwards motion of a tenth of an inch.
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As a practical matter, consider printing the mathematical symbol
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`>>'.
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The default spacing is too wide, so
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.UL eqn
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replaces this by
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.P1
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>\eh'\-0.3m'>
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.P2
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to produce >\h'-.3m'>.
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.PP
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Frequently
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.BD \eh
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is used with the `width function'
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.BD \ew
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to generate motions equal to the width
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of some character string.
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The construction
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.P1
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\ew'thing'
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.P2
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is a number equal to the width of `thing' in machine units
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(1/432 inch).
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All
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.UL troff
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computations are ultimately done in these units.
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To move horizontally the width of an `x',
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we can say
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.P1
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\eh'\ew'x'u'
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.P2
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As we mentioned above,
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the default scale factor for
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all horizontal dimensions is
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.BD m ,
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ems, so here we must have the
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.BD u
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for machine units,
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or the motion produced will be far too large.
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.UL troff
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is quite happy with the nested quotes, by the way,
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so long as you don't leave any out.
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.PP
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As a live example of this kind of construction,
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all of the command names in the text, like
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.BD .sp ,
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were done by overstriking with a slight offset.
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The commands for
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.BD .sp
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are
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.P1
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^sp\eh'\-\ew'.sp'u'\eh'1u'.sp
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.P2
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That is, put out `.sp', move left by the width of `.sp',
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move right 1 unit, and print
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`.sp' again.
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(Of course there is a way to avoid typing that much input
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for each command name, which we will discuss in Section 11.)
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.WS
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.PP
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There are also several special-purpose
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.UL troff
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commands for local motion.
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We have already seen
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.BD \e0 ,
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which is an unpaddable white space
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of the same width as a digit.
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`Unpaddable' means that it will never be widened
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or split across a line by line justification and filling.
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There is also
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.BD \e (blank),
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.tr ^^
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which is an unpaddable character the width of a space,
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.BD \e| ,
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which is half that width,
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.BD \e^ ,
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which is one quarter of the width of a space,
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and
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.BD \e& ,
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which has zero width.
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.tr ^.
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(This last one is useful, for example, in entering
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a text line which would otherwise begin with a `.'.)
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.PP
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The command
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.BD \eo ,
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used like
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.P1
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\eo'set of characters'
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.P2
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causes (up to 9)
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characters to be overstruck,
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centered on the widest.
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This is nice for accents, as in
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.P1 2
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syst\eo"e\e(ga"me t\eo"e\e(aa"l\eo"e\e(aa"phonique
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.P2
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which makes
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.P1
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syst\o"e\(ga"me t\o"e\(aa"l\o"e\(aa"phonique
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.P2
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The accents are
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.BD \e(ga
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and
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.BD \e(aa ,
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or
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.BD \e\`
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and
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.BD \e\' ;
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remember that each is just one character to
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.UL troff .
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.PP
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You can make your own overstrikes with another special convention,
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.BD \ez ,
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the zero-motion command.
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.BD \ezx
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suppresses the normal horizontal motion
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after printing the single character
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.BD x ,
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so another character can be laid on top of it.
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Although sizes can be changed within
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.BD \eo ,
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it centers the characters on the widest,
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and
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there can be no horizontal or vertical motions,
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so
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.BD \ez
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may be the only way to get what you want:
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.P1
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.sp 2
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\s8\z\(sq\s14\z\(sq\s22\z\(sq\s36\(sq
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.P2
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is produced by
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.P1
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^sp 2
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\es8\ez\e(sq\es14\ez\e(sq\es22\ez\e(sq\es36\e(sq
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.P2
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The
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.BD .sp
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is needed to leave room for the result.
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.PP
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As another example, an extra-heavy semicolon
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that looks like
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.P1
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\s+6\z,\v'-0.25m'.\v'0.25m'\s0 instead of ; or \s+6;\s0
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.P2
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can be constructed with a big comma and a big period above it:
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.P1
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\es+6\ez,\ev'\(mi0.25m'.\ev'0.25m'\es0
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.P2
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`0.25m' is an experimentally-derived constant.
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.PP
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A more ornate overstrike is given by the bracketing function
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.BD \eb ,
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which piles up characters vertically,
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centered on the current baseline.
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Thus we can get big brackets,
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constructing them with piled-up smaller pieces:
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.P1
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.sp
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.ne 3
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\b'\(lt\(lk\(lb' \b'\(lc\(lf' x \b'\(rc\(rf' \b'\(rt\(rk\(rb'
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.sp
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.P2
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by typing in only this:
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.P1 0
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\&^sp
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\eb\(fm\e(lt\e(lk\e(lb\(fm \eb\(fm\e(lc\e(lf\(fm x \eb\(fm\e(rc\e(rf\(fm \eb\(fm\e(rt\e(rk\e(rb\(fm
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.P2
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.PP
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.UL troff
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also provides a convenient facility for drawing horizontal and vertical
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lines of arbitrary length with arbitrary characters.
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.BD \el\(fm1i\(fm
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draws a line one inch long, like this:
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\l'1i'\|.
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The length can be followed by
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the character to use if the \(ru isn't appropriate;
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.BD \el\(fm0.5i.\(fm
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draws a half-inch line of dots: \l'.5i.'.
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The construction
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.BD \eL
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is entirely analogous,
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except that it draws a vertical line instead of horizontal.
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