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<?xml version="1.0" encoding="iso-8859-1"?>
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<title>Mom -- Graphical Objects</title>
</head>
<body bgcolor="#dfdfdf">
<!-- ==================================================================== -->
<a name="TOP"></a>
<p>
<a href="docprocessing.html#TOP">Next</a>
<a href="color.html#TOP">Prev</a>
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</p>
<h1 align="center"><a name="COLOR_INTRO"><u>Graphical objects</u></a></h1>
<p>
<a href="#INTRO_GRAPHICAL">Introduction to graphical objects</a>
<ul>
<li><a href="#BEHAVIOUR">Graphical object behaviour</a></li>
<li><a href="#ORDER">Order of arguments</a></li>
</ul>
<a href="#MACROS_GRAPHICAL">Index of graphical object macros</a>
</p>
<a name="INTRO_GRAPHICAL"><h2><u>Introduction to graphical objects</u></h2></a>
<p>
<strong>Groff</strong> has a number of
<a href="definitions.html#TERMS_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 <strong>groff</strong> info manual:
<pre>
info groff => Escape index => \D
</pre>
</p>
<p>
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 <em>consistent</em> manner, they don't
always perform in an <em>expected</em> 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, <strong>mom</strong> provides macros
to draw these objects in an easy-to-understand way; the results are
predictable, and <strong>mom</strong>'s syntax makes fixes or tweaks
painless.
</p>
<a name="GRAPHICAL_EXAMPLE"></a>
<p>
For example, if you want to draw a 2-inch square outline box at the left
margin using <strong>groff</strong>'s <kbd>\D</kbd> escapes, it looks like this:
<pre>
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
</pre>
Obviously, this isn't very efficient for something as simple as a
box.
</p>
<p>
Here's the same box, drawn with <strong>mom</strong>'s box drawing
macro,
<a href="#DBX">DBX</a>:
<pre>
left margin indent-+ +-box width
| |
.DBX .5 0 2i 2i
| |
rule weight--+ +-box depth
(in points)
</pre>
</p>
<p>
<strong>Mom</strong>'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 <strong>mom</strong>'a
graphical object macros, which means you must supply the arguments
every time you invoke them.
</p>
<p>
<strong>NOTE:</strong> As stated above, <strong>mom</strong> only
provides macros for commonly-used graphical objects (rules, boxes,
circles) only. More complex objects (polygons, non-straight lines,
splines) must be drawn using <strong>groff</strong>'s <kbd>\D</kbd>
escapes.
</p>
<a name="BEHAVIOUR"><h3><u>Graphical object behaviour</u></h3></a>
<p>
<strong>Mom</strong>'s graphical object macros all behave in the
following, carved-in-stone ways:
<ol>
<li>Objects are drawn from the
<a href="definitions.html#TERMS_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 <em>inward</em>.</li>
<li>Objects return to their horizontal/vertical point of origin.</li>
</ol>
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>
<a name="ORDER"><h3><u>Order of arguments</u></h3></a>
<p>
The order of arguments to the graphical object macros is the same
for every macro:
<ul>
<li>the <strong>Weight</strong> of the rule</li>
<ul>
<li>if the object is enclosed (i.e. is a box or circle), the
weight of the rule if you want the object outlined</li>
<li>the single word <kbd>SOLID</kbd> may be used in place
of the <strong>weight</strong> argument if you want the
object filled</li>
</ul>
<li>the <strong>Indent</strong> from the current left margin at
which to begin the object</li>
<li>the <strong>Length</strong> of the object, if applicable</li>
<li>the <strong>Depth</strong> of the object, if applicable</li>
<li>the <strong>Colour</strong> of the object (optional)</li>
</ul>
</p>
<p>
A simple mnemonic for the order of arguments is "WILD C".
If you fix the mnemonic in your brain and apply a little judicious
reasoning, you'll always remember how to draw graphical objects.
The "judicious reasoning" means that, for example,
horizontal rules don't require a depth and vertical rules don't
require a length. Thus, in the case of drawing a horizontal rule,
you supply the macro,
<a href="#DRH">DRH</a>,
with only the arguments (from the mnemonic) that apply: W-I-L (and
possibly C).
</p>
<a name="MACROS_GRAPHICAL"><h3><u>Index of graphical object macros</u></h3></a>
<ul>
<li><a href="#DRH">DRH</a>
— horizontal rule</li>
<li><a href="#DRV">DRV</a>
— vertical rule</li>
<li><a href="#DBX">DBX</a>
— box</li>
<li><a href="#DCL">DCL</a>
— circle or ellipse</li>
</ul>
<!-- -DRH- -->
<hr width="66%" align="left"/>
<a name="DRH"><h3><u>Drawing horizontal rules</u></h3></a>
<p>
<nobr>Macro: <strong>DRH</strong> <kbd><none> | <rule weight> <indent> <length> [<colour>]</kbd></nobr>
<br/>
<em>*The argument to</em> <kbd><rule weight></kbd> <em>is
in</em>
<a href="definitions.html#TERMS_PICASPOINTS">points</a>,
<em>but do </em> NOT <em>append the</em>
<a href="definitions.html#TERMS_UNITSOFMEASURE">unit of
measure</a>, <kbd>p</kbd>.
<br/>
<em>*The arguments,</em> <kbd><indent></kbd> <em>and</em>
<kbd><length></kbd>, <em>require a unit of measure.</em>
</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. (Note that <strong>DRH</strong> is the only graphical
object macro that may be invoked without arguments.) The weight of
the rule is determined by the argument you last gave the macro,
<a href="inlines.html#RULE_WEIGHT">RULE_WEIGHT</a>.
<strong>DRH</strong>, used this way, is exactly equivalent to
entering the
<a href="definitions.html#TERMS_INLINES">inline escape</a>,
<a href="inlines.html#INLINE_RULE_MOM"><kbd>\*[RULE]</kbd></a>.
</p>
<p>
To draw horizontal rules of a specified length, you must, at a
minimum, supply
<strong>DRH</strong> with the arguments
<kbd><nobr>rule weight,</nobr> indent</kbd> (measured from the
current left margin) and <kbd>length</kbd>.
</p>
<p>
Optionally, you may give a <kbd>colour</kbd> argument.
The colour may be either one defined with
<a href="color.html#NEWCOLOR">NEWCOLOR</a>,
or a named X-colour inititialized with
<a href="color.html#XCOLOR">XCOLOR</a>,
or an X-colour alias (again, initialized with
<strong>XCOLOR</strong>).
</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:
<pre>
weight length
| |
.DRH 1.125 2P 3i
|
indent
</pre>
(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:
<pre>
.DRH 1.125 2P 3i blue
</pre>
</p>
<h3><u>How mom handles the positioning of horizontal rules</u></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, <strong>mom</strong> returns
you to the current left margin, at the same vertical position on
the page as when <strong>DRH</strong> was invoked. In other words,
<strong>DRH</strong> causes no movement on the page, either
horizontal or vertical.
</p>
<!-- -DRV- -->
<hr width="33%" align="left"/>
<a name="DRV"><h3><u>Drawing vertical rules</u></h3></a>
<p>
<nobr>Macro: <strong>DRV</strong> <kbd><rule weight> <indent> <depth> [<colour>]</kbd></nobr>
<br/>
<em>*The argument to</em> <kbd><rule weight></kbd> <em>is
in</em>
<a href="definitions.html#TERMS_PICASPOINTS">points</a>,
<em>but do </em> NOT <em>append the</em>
<a href="definitions.html#TERMS_UNITSOFMEASURE">unit of
measure</a>, <kbd>p</kbd>.
<br/>
<em>*The arguments,</em> <kbd><indent></kbd> <em>and</em>
<kbd><depth></kbd>, <em>require a unit of measure.</em>
</p>
<p>
To draw vertical rules of a specified length, you must, at a
minimum, supply
<strong>DRV</strong> with the arguments
<kbd><nobr>rule weight,</nobr> indent</kbd> (measured from the
current left margin) and <kbd>depth</kbd>.
</p>
<p>
Optionally, you may give a <kbd>colour</kbd> argument.
The colour may be either one defined with
<a href="color.html#NEWCOLOR">NEWCOLOR</a>,
or a named X-colour inititialized with
<a href="color.html#XCOLOR">XCOLOR</a>,
or an X-colour alias (again, initialized with
<strong>XCOLOR</strong>).
</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 centimeters. To do so, you'd invoke <kbd>.DRV</kbd> like this:
<pre>
weight depth
| |
.DRV .75 19P+6p 6c
|
indent
</pre>
(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:
<pre>
.DRV .75 19P+6p 6c red
</pre>
</p>
<h3><u>How mom handles the positioning of vertical rules</u></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 left of the indent given to <strong>DRV</strong>.
</p>
<p>
Furthermore, after the rule is drawn, <strong>mom</strong> returns
you to the current left margin, at the same vertical position
on the page as when <strong>DRV</strong> was invoked. In other
words, <strong>DRV</strong> causes no movement on the page, either
horizontal or vertical.
</p>
<!-- -DBX- -->
<hr width="33%" align="left"/>
<a name="DBX"><h3><u>Drawing boxes</u></h3></a>
<p>
<nobr>Macro: <strong>DBX</strong> <kbd>< <rule weight> | SOLID > <indent> <length> <depth> [<colour>]</kbd></nobr>
<br/>
<em>*The argument to</em> <kbd><rule weight></kbd> <em>is
in</em>
<a href="definitions.html#TERMS_PICASPOINTS">points</a>,
<em>but do </em> NOT <em>append the</em>
<a href="definitions.html#TERMS_UNITSOFMEASURE">unit of
measure</a>, <kbd>p</kbd>.
<br/>
<em>*The arguments,</em> <kbd><indent></kbd><em>,</em>
<kbd><length></kbd> <em>and</em> <kbd><depth></kbd>
<em>require a unit of measure.</em>
</p>
<p>
To draw boxes of specified dimensions, you must, at a minimum,
supply <strong>DBX</strong> with the arguments <kbd><nobr>rule
weight</nobr></kbd> or <kbd>SOLID</kbd>, <kbd>indent</kbd>
(measured from the current left margin), <kbd>length</kbd> and
<kbd>depth</kbd>.
</p>
<p>
Optionally, you may give a <kbd>colour</kbd> argument.
The colour may be either one defined with
<a href="color.html#NEWCOLOR">NEWCOLOR</a>,
or a named X-colour inititialized with
<a href="color.html#XCOLOR">XCOLOR</a>,
or an X-colour alias (again, initialized with
<strong>XCOLOR</strong>).
</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:
<pre>
indent depth
| |
.DBX .5 1i 12P 6P
| |
weight length
</pre>
(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>
If you want the same box, but solid ("filled") rather
than drawn as an outline:
<pre>
.DBX SOLID 1i 12P 6P
</pre>
<p>
Additionally, if you want the box green:
<pre>
.DBX .5 1i 12P 6P green
or
.DBX SOLID 1i 12P 6P green
</pre>
</p>
<h3><u>How mom handles the positioning of boxes</u></h3>
<p>
Boxes are drawn from the baseline down, from left to right, and
from the perimeter <em>inward</em>. "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
<em>within</em> the dimensions of the box.
</p>
<p>
Furthermore, after the box is drawn, <strong>mom</strong> returns
you to the current left margin, at the same vertical position
on the page as when <strong>DBX</strong> was invoked. In other
words, <strong>DBX</strong> causes no movement on the page, either
horizontal or vertical.
</p>
<!-- -DCL- -->
<hr width="33%" align="left"/>
<a name="DCL"><h3><u>Drawing circles (ellipses)</u></h3></a>
<p>
<nobr>Macro: <strong>DCL</strong> <kbd>< <rule weight> | SOLID > <indent> <length> <depth> [<colour>]</kbd></nobr>
<br/>
<em>*The argument to</em> <kbd><rule weight></kbd> <em>is
in</em>
<a href="definitions.html#TERMS_PICASPOINTS">points</a>,
<em>but do </em> NOT <em>append the</em>
<a href="definitions.html#TERMS_UNITSOFMEASURE">unit of
measure</a>, <kbd>p</kbd>.
<br/>
<em>*The arguments,</em> <kbd><indent></kbd><em>,</em>
<kbd><length></kbd> <em>and</em> <kbd><depth></kbd>
<em>require a unit of measure.</em>
</p>
<p>
To draw circles of specified dimensions, you must, at a minimum,
supply <strong>DCL</strong> with the arguments <kbd><nobr>rule
weight</nobr></kbd> or <kbd>SOLID</kbd>, <kbd>indent</kbd>
(measured from the current left margin), <kbd>length</kbd> and
<kbd>depth</kbd>.
</p>
<p>
Optionally, you may give a <kbd>colour</kbd> argument.
The colour may be either one defined with
<a href="color.html#NEWCOLOR">NEWCOLOR</a>,
or a named X-colour inititialized with
<a href="color.html#XCOLOR">XCOLOR</a>,
or an X-colour alias (again, initialized with
<strong>XCOLOR</strong>).
</p>
<p>
Say, for example, you want to draw a 1/2 point outline circle
(ellipse, actually, in this case) that starts one inch from the
current left margin and has the dimensions 6 centimeters x 3
centimeters. To do so, you'd invoke <kbd>.DCL</kbd> like this:
<pre>
indent depth
| |
.DCL .5 1i 6c 3c
| |
weight ength
</pre>
(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>
If you want the same box, but solid ("filled") rather
than drawn as an outline:
<pre>
.DCL SOLID 1i 6c 3c
</pre>
<p>
Additionally, if you want the circle yellow:
<pre>
.DCL .5 1i 6c 3c yellow
or
.DCL SOLID 1i 6c 3c yellow
</pre>
</p>
<h3><u>How mom handles the positioning of circles (ellipses)</u></h3>
<p>
Circles (ellipses) are drawn from the baseline down, from left
to right, and from the perimeter <em>inward</em>. "From the
perimeter inward" means that if you request a box weight of six
points, the 6-point rule used to draw the outline of the circle or
ellipse falls entirely <em>within</em> the dimensions of the circle
or ellipse.
</p>
<p>
Furthermore, after the circle is drawn, <strong>mom</strong> returns
you to the current left margin, at the same vertical position
on the page as when <strong>DCL</strong> was invoked. In other
words, <strong>DCL</strong> causes no movement on the page, either
horizontal or vertical.
</p>
<hr/>
<p>
<a href="docprocessing.html#TOP">Next</a>
<a href="color.html#TOP">Prev</a>
<a href="#TOP">Top</a>
<a href="toc.html">Back to Table of Contents</a>
</p>
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