1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
|
<!DOCTYPE html>
<html>
<!-- Created by GNU Texinfo 7.0.3, https://www.gnu.org/software/texinfo/ -->
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<!-- This manual documents GNU troff version 1.23.0.
Copyright � 1994-2023 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A
copy of the license is included in the section entitled "GNU Free
Documentation License". -->
<title>Vertical Position Traps (The GNU Troff Manual)</title>
<meta name="description" content="Vertical Position Traps (The GNU Troff Manual)">
<meta name="keywords" content="Vertical Position Traps (The GNU Troff Manual)">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<meta name="viewport" content="width=device-width,initial-scale=1">
<link href="index.html" rel="start" title="Top">
<link href="Request-Index.html" rel="index" title="Request Index">
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
<link href="Traps.html" rel="up" title="Traps">
<link href="Page-Location-Traps.html" rel="next" title="Page Location Traps">
<link href="Traps.html" rel="prev" title="Traps">
<style type="text/css">
<!--
a.copiable-link {visibility: hidden; text-decoration: none; line-height: 0em}
span.r {font-family: initial; font-weight: normal; font-style: normal}
span:hover a.copiable-link {visibility: visible}
strong.def-name {font-family: monospace; font-weight: bold; font-size: larger}
-->
</style>
</head>
<body lang="en">
<div class="subsection-level-extent" id="Vertical-Position-Traps">
<div class="nav-panel">
<p>
Next: <a href="Page-Location-Traps.html" accesskey="n" rel="next">Page Location Traps</a>, Previous: <a href="Traps.html" accesskey="p" rel="prev">Traps</a>, Up: <a href="Traps.html" accesskey="u" rel="up">Traps</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Request-Index.html" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<h4 class="subsection" id="Vertical-Position-Traps-1">5.28.1 Vertical Position Traps</h4>
<a class="index-entry-id" id="index-vertical-position-traps"></a>
<a class="index-entry-id" id="index-traps_002c-vertical-position"></a>
<p>A <em class="dfn">vertical position trap</em> calls a macro when the formatter’s
vertical drawing position reaches or passes, in the downward direction,
a certain location on the output page or in a diversion. Its
applications include setting page headers and footers, body text in
multiple columns, and footnotes.
</p>
<dl class="first-deffn">
<dt class="deffn" id="index-_002evpt"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.vpt</code></strong> <var class="def-var-arguments">[<span class="r"><i class="slanted">flag</i></span>]</var><a class="copiable-link" href='#index-_002evpt'> ¶</a></span></dt>
<dd><a class="index-entry-id" id="index-vpt"></a>
</dd><dt class="deffnx def-cmd-deffn" id="index-_005cn_005b_002evpt_005d"><span class="category-def">Register: </span><span><strong class="def-name"><code class="t">\n[.vpt]</code></strong><a class="copiable-link" href='#index-_005cn_005b_002evpt_005d'> ¶</a></span></dt>
<dd><a class="index-entry-id" id="index-_002evpt-1"></a>
<a class="index-entry-id" id="index-enabling-vertical-position-traps-_0028vpt_0029"></a>
<a class="index-entry-id" id="index-vertical-position-traps_002c-enabling-_0028vpt_0029"></a>
<a class="index-entry-id" id="index-vertical-position-trap-enable-register-_0028_002evpt_0029"></a>
<p>Enable vertical position traps if <var class="var">flag</var> is non-zero or absent;
disable them otherwise. Vertical position traps are those set by the
<code class="code">wh</code> request or by <code class="code">dt</code> within a diversion. The parameter
that controls whether vertical position traps are enabled is global.
Initially, vertical position traps are enabled. The current value is
stored in the <code class="code">.vpt</code> read-only register.
</p>
<a class="index-entry-id" id="index-page-break_002c-prevented-by-vpt"></a>
<a class="index-entry-id" id="index-break_002c-page_002c-prevented-by-vpt"></a>
<a class="index-entry-id" id="index-page-ejection_002c-prevented-by-vpt"></a>
<a class="index-entry-id" id="index-ejection_002c-page_002c-prevented-by-vpt"></a>
<p>A page can’t be ejected if <code class="code">vpt</code> is set to zero; see <a class="ref" href="The-Implicit-Page-Trap.html">The Implicit Page Trap</a>.
</p></dd></dl>
<ul class="mini-toc">
<li><a href="Page-Location-Traps.html" accesskey="1">Page Location Traps</a></li>
<li><a href="The-Implicit-Page-Trap.html" accesskey="2">The Implicit Page Trap</a></li>
<li><a href="Diversion-Traps.html" accesskey="3">Diversion Traps</a></li>
</ul>
</div>
</body>
</html>
|
