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|
<?xml version="1.0" encoding="utf-8"?>
<!--
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Copyright (C) 2004-2020 Free Software Foundation, Inc.
Written by Peter Schaffter (peter@schaffter.ca).
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<title>Mom -- Graphical Objects</title>
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</head>
<body style="background-color: #f5faff;">
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<h1 class="docs">Graphical objects</h1>
<div style="text-align: center;">
<ul class="no-enumerator" style="margin-left: -2.5em;">
<li><a href="#intro-graphical">Introduction to graphical objects</a></li>
<li><a href="#behaviour">Graphical objects behaviour</a></li>
<li><a href="#order">Order of arguments</a></li>
<li><a href="#index-graphical">Index of graphical objects macros</a></li>
</ul>
</div>
<div class="rule-medium"><hr/></div>
<h2 id="intro-graphical" class="docs">Introduction to graphical objects</h2>
<p>
Groff has a number of
<a href="definitions.html#inlines">inline escapes</a>
for drawing rules, polygons, ellipses and splines. All begin with
<kbd>\D</kbd> (presumably for “Draw”) and are documented
in the groff info manual:
<br/>
<span class="pre-in-pp">
info groff \D
</span>
The escapes allow you to draw just about any simple graphical object
you can think of, but owing to their syntax they’re not always easy
to read, which can make tweaking them difficult. Additionally,
while they perform in a <i>consistent</i> manner, they don’t
always perform in an <i>expected</i> manner.
</p>
<p>
Experience shows that the most common graphical elements typesetters
need are rules (horizontal and vertical), boxes, and circles (or
ellipses). For this reason, mom provides macros
to draw these objects in an easy-to-understand way; the results are
predictable, and mom’s syntax makes fixes or tweaks
painless.
</p>
<p id="graphical-example">
For example, if you want to draw a 2-inch square outline box at the left
margin using groff’s <kbd>\D</kbd> escapes, it looks like this:
<br/>
<span class="pre-in-pp">
back up
by
weight
+-------+
| |
\D't 500'\h'-500u'\D'p 2i 0 0 2i -2i 0 0 -2i'
| | | |
+-------+ +------------------------+
set rule draw box, 1 line at a time
weight
</span>
Obviously, this isn’t very efficient for something as simple as a
box.
</p>
<p>
Here’s the same box, drawn with mom’s box drawing
macro
<kbd><a href="#dbx">DBX</a></kbd>:
<br/>
<span class="pre-in-pp">
left margin indent--+ +--box width
| |
.DBX .5 0 2i 2i
| |
rule weight--+ +--box depth
(in points)
</span>
</p>
<p>
Mom’s graphical object macros allow—in fact,
require—giving the rule weight (“thickness”) for
the object (or saying that you want it filled), an indent from the
left margin where the object begins, the dimensions of the object,
and optionally a colour for the object.
</p>
<p>
There are no defaults for the arguments to mom’s graphical
object macros, which means you must supply the arguments every time
you invoke them.
</p>
<div class="box-tip">
<p class="tip">
<span class="note">Note:</span>
As stated above, mom only provides macros for commonly-used
graphical objects (rules, boxes, circles). More complex objects
(polygons, non-straight lines, splines) must be drawn using
groff’s <kbd>\D</kbd> escapes.
</p>
</div>
<h3 id="behaviour" class="docs">Graphical object behaviour</h3>
<p>
Mom’s graphical object macros all behave in the following,
carved-in-stone ways:
</p>
<ol style="margin-top: -.5em; margin-bottom: -.5em;">
<li>Objects are drawn from the
<a href="definitions.html#baseline">baseline</a>
down, including horizontal rules.</li>
<li>Objects begin precisely at the left indent supplied as
an argument to the macro.</li>
<li>Objects are drawn from left to right.</li>
<li>Enclosed objects (boxes, circles) are drawn from the
perimeter <i>inward</i>.</li>
<li>Objects return to their horizontal/vertical point of origin.</li>
</ol>
<p>
The consistency means that once you’ve mastered the very
simple order of arguments that applies to invoking graphical
object macros, you can draw objects with full confidence that you
know exactly where they’re placed and how much room they
occupy. Furthermore, because all return to their point of origin,
you’ll know exactly where you are on the page.
</p>
<h3 id="order" class="docs">Order of arguments</h3>
<p>
The order of arguments to the graphical object macros is the same
for every macro:
</p>
<ul style="margin-top: -.5em; margin-bottom: -.5em;">
<li>the rule weight
<ul style="margin-left: -.75em;">
<li>the single word <kbd>SOLID</kbd> may be used in place
of <kbd>weight</kbd> if you want boxes or circles filled</li>
</ul></li>
<li>the indent from the current left margin at which to begin
the object
</li>
<li>the width of the object if applicable</li>
<li>the depth of the object if applicable</li>
<li>the colour of the object (optional)</li>
</ul>
<div class="macro-list-container">
<h3 id="index-graphical" class="macro-list">Graphical objects macros</h3>
<ul class="macro-list">
<li><a href="#drh">DRH</a>
– horizontal rules</li>
<li><a href="#drv">DRV</a>
– vertical rules</li>
<li><a href="#dbx">DBX</a>
– box</li>
<li><a href="#dcl">DCL</a>
– circles or ellipses</li>
</ul>
</div>
<!-- -DRH- -->
<div class="macro-id-overline">
<h3 id="drh" class="macro-id">Drawing horizontal rules</h3>
</div>
<div class="box-macro-args">
Macro: <b>DRH</b> <kbd class="macro-args"><none> | <weight> <indent> <width> [<colour>]</kbd>
</div>
<p class="requires">
•
the argument to <kbd class="normal"><weight></kbd> is in
<a href="definitions.html#picaspoints" class="normal">points</a>,
but do <span class="normal">not</span> append the
<a href="definitions.html#unitsofmeasure">unit of measure</a>,
<kbd class="normal">p</kbd>
<br/>
•
<kbd class="normal"><indent></kbd>
and
<kbd class="normal"><width></kbd>
require a unit of measure
<br/>
•
arithmetic expressions to
<kbd class="normal"><indent></kbd>
and
<kbd class="normal"><width></kbd>
must be surrounded by parentheses
</p>
<p>
If all you want is to draw a rule from your current left
margin to your current right margin (in other words, a "full
measure" rule), you may invoke <kbd>.DRH</kbd> without any
arguments.
</p>
<div class="box-tip">
<p class="tip">
<span class="note">Note:</span>
DRH is the only graphical object macro that may be invoked
without arguments. The weight (“thickness”) of
the rule is determined by the argument you last gave the
macro
<a href="inlines.html#rule-weight">RULE_WEIGHT</a>.
DRH, used this way, is exactly equivalent to entering the
<a href="definitions.html#inlines">inline escape</a>
<a href="inlines.html#inline-rule-mom"><kbd><span class="nobr">\*[RULE]</span></kbd></a>.
</p>
</div>
<p style="margin-top: -.5em;">
To draw horizontal rules of a specified width, you must, at
a minimum, supply DRH with the arguments <kbd>weight,</kbd>
<kbd>indent</kbd> (measured from the current left margin) and
<kbd>width</kbd>.
</p>
<p>
Optionally, you may give a <kbd>color</kbd> argument. The colour
may be either one defined with
<a href="color.html#newcolor">NEWCOLOR</a>,
or a named X-color initialized with
<a href="color.html#xcolor">XCOLOR</a>,
or an X-color alias (again, initialized with XCOLOR).
</p>
<p>
Say, for example, you want to draw a 1-1/4 point horizontal rule
that starts 2 picas from the current left margin and runs for 3
inches. To do so, you’d invoke <kbd>.DRH</kbd> like this:
<br/>
<span class="pre-in-pp">
weight width
| |
.DRH 1.25 2P 3i
|
indent
</span>
(Note that the rule weight argument, which is expressed in points,
must not have the unit of measure <kbd>p</kbd> appended to it.)
</p>
<p>
If, in addition, you want the rule blue:
<br/>
<span class="pre-in-pp">
.DRH 1.25 2P 3i blue
</span>
</p>
<h3 class="docs">How mom handles the positioning of horizontal rules</h3>
<p>
Horizontal rules are drawn from left to right, and from the baseline
down. “From the baseline down” means that if you request
a rule with a weight of four points, the four points of rule fall
entirely below the baseline.
</p>
<p>
Furthermore, after the rule is drawn, mom returns you to the current
left margin, at the same vertical position on the page as when DRH
was invoked. In other words, DRH causes no movement on the page,
either horizontal or vertical.
</p>
<!-- -DRV- -->
<div class="macro-id-overline">
<h3 id="drv" class="macro-id">Drawing vertical rules</h3>
</div>
<div class="box-macro-args">
Macro: <b>DRV</b> <kbd class="macro-args"><weight> <indent> <depth> [<colour>]</kbd>
</div>
<p class="requires">
•
the argument to <kbd class="normal"><weight></kbd> is in
<a href="definitions.html#picaspoints" class="normal">points</a>,
but do <span class="normal">not</span> append the
<a href="definitions.html#unitsofmeasure">unit of measure</a>,
<kbd class="normal">p</kbd>
<br/>
•
<kbd class="normal"><indent></kbd>
and
<kbd class="normal"><depth></kbd>
require a unit of measure
<br/>
•
arithmetic expressions to
<kbd class="normal"><indent></kbd>
and
<kbd class="normal"><depth></kbd>
must be surrounded by parentheses
</p>
<p>
To draw vertical rules of a specified depth, you must, at
a minimum, supply DRV with the arguments <kbd>weight,</kbd>
<kbd>indent</kbd> (measured from the current left margin) and
<kbd>depth</kbd>.
</p>
<p>
Optionally, you may give a <kbd>color</kbd> argument. The colour
may be either one defined with
<a href="color.html#newcolor">NEWCOLOR</a>,
or a named X-color initialized with
<a href="color.html#xcolor">XCOLOR</a>,
or an X-color alias (again, initialized with XCOLOR).
</p>
<p>
Say, for example, you want to draw a 3/4-point vertical rule that
starts 19-1/2 picas from the current left margin and has a depth of
6 centimetres. To do so, you’d invoke <kbd>.DRV</kbd> like
this:
<br/>
<span class="pre-in-pp">
weight depth
| |
.DRV .75 19P+6p 6c
|
indent
</span>
(Note that the rule weight argument, which is expressed in points,
must not have the unit of measure <kbd>p</kbd> appended to it.)
</p>
<p>
If, in addition, you want the rule red:
<br/>
<span class="pre-in-pp">
.DRV .75 19P+6p 6c red
</span>
</p>
<h3 class="docs">How mom handles the positioning of vertical rules</h3>
<p>
Vertical rules are drawn from the baseline down, and from left to
right. "Left to right" means that if you request a rule
with a weight of four points, the four points of rule fall entirely
to the right of the indent given to DRV.
</p>
<p>
Furthermore, after the rule is drawn, mom returns you to the current
left margin, at the same vertical position on the page as when DRV
was invoked. In other words, DRV causes no movement on the page,
either horizontal or vertical.
</p>
<!-- -DBX- -->
<div class="macro-id-overline">
<h3 id="dbx" class="macro-id">Drawing boxes</h3>
</div>
<div class="box-macro-args">
Macro: <b>DBX</b> <kbd class="macro-args"><weight>|SOLID <indent> <width>|FULL_MEASURE <depth> [<color>]</kbd>
</div>
<p class="requires">
•
the argument to <kbd class="normal"><weight></kbd> is in
<a href="definitions.html#picaspoints" class="normal">points</a>,
but do <span class="normal">not</span> append the
<a href="definitions.html#unitsofmeasure">unit of measure</a>
<kbd class="normal">p</kbd>
<br/>
• <kbd class="normal"><indent></kbd>,
<kbd class="normal"><width></kbd>,
and
<kbd class="normal"><depth></kbd>
require a unit of measure
<br/>
•
arithmetic expressions to
<kbd class="normal"><indent></kbd>,
<kbd class="normal"><width></kbd>,
and
<kbd class="normal"><depth></kbd>
must be enclosed in parentheses.
</p>
<p>
To draw boxes you must, at a minimum, supply DBX with the arguments
<kbd>weight</kbd> or <kbd>SOLID</kbd>, <kbd>indent</kbd>,
<kbd>width</kbd> or <kbd>FULL_MEASURE</kbd>, and <kbd>depth</kbd>.
</p>
<p>
<kbd>weight</kbd> is the rule weight of outlined boxes, given in
points but without the
<a href="definitions.html#unitsofmeasure">unit of measure</a>
<kbd>p</kbd> appended.
</p>
<p>
If <kbd>SOLID</kbd> is given as the first argument, the box is
filled rather than outlined and no <kbd>weight</kbd> argument should
be supplied.
</p>
<p>
<kbd>indent</kbd> is measured from the current left margin. If
<kbd>FULL_MEASURE</kbd> is given, <kbd>indent</kbd> should be set to
“0”.
</p>
<p>
<kbd>width</kbd> is the width of the box with a
<a href="definitions.html#unitsofmeasure">unit of measure</a>
appended, caclculated from <kbd>indent</kbd> argument.
</p>
<p>
If <kbd>FULL_MEASURE</kbd> is given instead of <kbd>width</kbd>,
it circumvents having to calculate the width when left and/or right
indents are in effect; mom draws the box from the current left
margin to the current right margin. When no indents are in effect,
<kbd>FULL_MEASURE</kbd> or <kbd>\n[.l]u</kbd>—the groff
way of saying “the current line length”—have the
same effect.
</p>
<p>
Optionally, you may give a <kbd>color</kbd> argument. The colour
may be either one defined with
<a href="color.html#newcolor">NEWCOLOR</a>,
or a named X-color initialized with
<a href="color.html#xcolor">XCOLOR</a>,
or an X-color alias (again, initialized with XCOLOR).
</p>
<p>
Say, for example, you want to draw a 1/2 point outline box that
starts one inch from the current left margin and has the dimensions
12 picas x 6 picas. To do so, you’d invoke <kbd>.DBX</kbd>
like this:
<br/>
<span class="pre-in-pp">
indent depth
| |
.DBX .5 1i 12P 6P
| |
weight width
</span>
(Note that the box weight argument, which is expressed in points,
must not have the unit of measure <kbd>p</kbd> appended to it.)
</p>
<p>
If you want the same box, but solid (“filled”) rather
than drawn as an outline:
<br/>
<span class="pre-in-pp">
.DBX SOLID 1i 12P 6P
</span>
Additionally, if you want the box green:
<br/>
<span class="pre-in-pp">
.DBX .5 1i 12P 6P green
</span>
or
<span class="pre-in-pp">
.DBX SOLID 1i 12P 6P green
</span>
</p>
<h3 class="docs">How mom handles the positioning of boxes</h3>
<p>
Boxes are drawn from the baseline down, from left to right, and
from the perimeter <i>inward</i>. “From the perimeter
inward” means that if you request a box weight of six points,
the 6-point rules used to draw the outline of the box fall entirely
<i>within</i> the dimensions of the box.
</p>
<p>
Furthermore, after the box is drawn, mom returns you to the current
left margin, at the same vertical position on the page as when DBX
was invoked. In other words, DBX causes no movement on the page,
either horizontal or vertical.
</p>
<!-- -DCL- -->
<div class="macro-id-overline">
<h3 id="dcl" class="macro-id">Drawing circles (ellipses)</h3>
</div>
<div class="box-macro-args">
Macro: <b>DCL</b> <kbd class="macro-args"><weight>|SOLID <indent> <width>|FULL_MEASURE <depth> [<color>]</kbd>
</div>
<p class="requires">
•
the argument to <kbd class="normal"><weight></kbd> is in
<a href="definitions.html#picaspoints" class="normal">points</a>,
but do <span class="normal">not</span> append the
<a href="definitions.html#unitsofmeasure">unit of measure</a>
<kbd class="normal">p</kbd>
<br/>
• <kbd class="normal"><indent></kbd>,
<kbd class="normal"><width></kbd>,
and
<kbd class="normal"><depth></kbd>
require a unit of measure
<br/>
•
arithmetic expressions to
<kbd class="normal"><indent></kbd>,
<kbd class="normal"><width></kbd>,
and
<kbd class="normal"><depth></kbd>
must be enclosed in parentheses.
</p>
<p>
To draw circles you must, at a minimum, supply DCL with the arguments
<kbd>weight</kbd> or <kbd>SOLID</kbd>, <kbd>indent</kbd>,
<kbd>width</kbd> or <kbd>FULL_MEASURE</kbd>, and <kbd>depth</kbd>.
</p>
<p>
<kbd>weight</kbd> is the rule weight of outlined circles, given in
points but without the unit of measure
<a href="definitions.html#unitsofmeasure">unit of measure</a>
<kbd>p</kbd> appended.
</p>
<p>
If <kbd>SOLID</kbd> is given as the first argument, the circle is
filled rather than outlined and no <kbd>weight</kbd> argument should
be supplied.
</p>
<p>
<kbd>indent</kbd> is measured from the current left margin. If
<kbd>FULL_MEASURE</kbd> is given, <kbd>indent</kbd> should be set to
“0”.
</p>
<p>
<kbd>width</kbd> is the width of the circle with a
<a href="definitions.html#unitsofmeasure">unit of measure</a>
appended, caclculated from <kbd>indent</kbd> argument.
</p>
<p>
If <kbd>FULL_MEASURE</kbd> is given instead of <kbd>width</kbd>,
it circumvents having to calculate the width when left and/or right
indents are in effect; mom draws the circle from the current left
margin to the current right margin. When no indents are in effect,
<kbd>FULL_MEASURE</kbd> or <kbd>\n[.l]u</kbd>—the groff
way of saying “the current line length”—have the
same effect.
</p>
<p>
Optionally, you may give a <kbd>color</kbd> argument. The colour
may be either one defined with
<a href="color.html#newcolor">NEWCOLOR</a>,
or a named X-color initialized with
<a href="color.html#xcolor">XCOLOR</a>,
or an X-color alias (again, initialized with XCOLOR).
</p>
<p>
Say, for example, you want to draw a 1/2 point outline circle that
starts one inch from the current left margin and has the dimensions
12 picas x 6 picas. To do so, you’d invoke <kbd>.DCL</kbd>
like this:
<br/>
<span class="pre-in-pp">
indent depth
| |
.DCL .5 1i 12P 6P
| |
weight width
</span>
(Note that the circle weight argument, which is expressed in points,
must not have the unit of measure <kbd>p</kbd> appended to it.)
</p>
<p>
If you want the same circle, but solid (“filled”) rather
than drawn as an outline:
<br/>
<span class="pre-in-pp">
.DCL SOLID 1i 12P 6P
</span>
Additionally, if you want the circle green:
<br/>
<span class="pre-in-pp">
.DCL .5 1i 12P 6P green
</span>
or
<span class="pre-in-pp">
.DCL SOLID 1i 12P 6P green
</span>
</p>
<h3 class="docs">How mom handles the positioning of circles (ellipses)</h3>
<p>
Circles (ellipses) are drawn from the baseline down, from left
to right, and from the perimeter <i>inward</i>. “From the
perimeter inward” means that if you request a circle weight of
six points, the 6-point rule used to draw the outline of the circle
or ellipse falls entirely <i>within</i> the dimensions of the
circle or ellipse.
</p>
<p>
Furthermore, after the circle is drawn, mom returns you to the
current left margin, at the same vertical position on the page as
when DCL was invoked. In other words, DCL causes no movement on the
page, either horizontal or vertical.
</p>
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