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+<html>
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+under the terms of the GNU Free Documentation License, Version 1.3 or
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+<title>Suppressing Output (The GNU Troff Manual)</title>
+
+<meta name="description" content="Suppressing Output (The GNU Troff Manual)">
+<meta name="keywords" content="Suppressing Output (The GNU Troff Manual)">
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+<div class="section-level-extent" id="Suppressing-Output">
+<div class="nav-panel">
+<p>
+Next: <a href="Colors.html" accesskey="n" rel="next">Colors</a>, Previous: <a href="Environments.html" accesskey="p" rel="prev">Environments</a>, Up: <a href="GNU-troff-Reference.html" accesskey="u" rel="up">GNU <code class="code">troff</code> Reference</a> &nbsp; [<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>
+<h3 class="section" id="Suppressing-Output-1">5.32 Suppressing Output</h3>
+
+<dl class="first-deffn">
+<dt class="deffn" id="index-_005cO_005bnum_005d"><span class="category-def">Escape&nbsp;sequence: </span><span><strong class="def-name"><code class="t">\O[</code><span class="r"><i class="slanted">num</i></span><code class="t">]</code></strong><a class="copiable-link" href='#index-_005cO_005bnum_005d'> &para;</a></span></dt>
+<dd><a class="index-entry-id" id="index-_005cO"></a>
+<a class="index-entry-id" id="index-suppressing-output-_0028_005cO_0029"></a>
+<a class="index-entry-id" id="index-output_002c-suppressing-_0028_005cO_0029"></a>
+<p>Suppress GNU <code class="code">troff</code> output of glyphs and geometric objects. The
+sequences <code class="code">\O2</code>, <code class="code">\O3</code>, <code class="code">\O4</code>, and <code class="code">\O5</code> are
+intended for internal use by <code class="code">grohtml</code>.
+</p>
+<dl class="table">
+<dt>&lsquo;<samp class="samp">\O0</samp>&rsquo;</dt>
+<dd><p>Disable the emission of glyphs and geometric objects to the output
+driver, provided that this sequence occurs at the outermost suppression
+level (see <code class="code">\O3</code> and <code class="code">\04</code> below). Horizontal motions
+corresponding to non-overstruck glyph widths still occur.
+</p>
+</dd>
+<dt>&lsquo;<samp class="samp">\O1</samp>&rsquo;</dt>
+<dd><p>Enable the emission of glyphs and geometric objects to the output
+driver, provided that this sequence occurs at the outermost suppression
+level.
+</p></dd>
+</dl>
+
+<a class="index-entry-id" id="index-opminx"></a>
+<a class="index-entry-id" id="index-opminy"></a>
+<a class="index-entry-id" id="index-opmaxx"></a>
+<a class="index-entry-id" id="index-opmaxy"></a>
+<p><code class="code">\O0</code> and <code class="code">\O1</code> also reset the four registers <code class="code">opminx</code>,
+<code class="code">opminy</code>, <code class="code">opmaxx</code>, and <code class="code">opmaxy</code> to &minus;1. These
+four registers mark the top left and bottom right hand corners of a box
+encompassing all written or drawn output.
+</p>
+<dl class="table">
+<dt>&lsquo;<samp class="samp">\O2</samp>&rsquo;</dt>
+<dd><p>At the outermost suppression level, enable emission of glyphs and
+geometric objects, and write to the standard error stream the page
+number and values of the four aforementioned registers encompassing
+glyphs written since the last interpolation of a <code class="code">\O</code> sequence, as
+well as the page offset, line length, image file name (if any),
+horizontal and vertical device motion quanta, and input file name.
+Numeric values are in basic units.
+</p>
+</dd>
+<dt>&lsquo;<samp class="samp">\O3</samp>&rsquo;</dt>
+<dd><p>Begin a nested suppression level. <code class="command">grohtml</code> uses this mechanism
+to create images of output preprocessed with <code class="command">gpic</code>,
+<code class="command">geqn</code>, and <code class="command">gtbl</code>. At startup, GNU <code class="code">troff</code> is at
+the outermost suppression level. <code class="command">pre-grohtml</code> generates these
+sequences when processing the document, using GNU <code class="command">troff</code> with
+the <code class="code">ps</code> output device, Ghostscript, and the PNM tools to produce
+images in PNG format. They start a new page if the device is not
+<code class="code">html</code> or <code class="code">xhtml</code>, to reduce the number of images crossing a
+page boundary.
+</p>
+</dd>
+<dt>&lsquo;<samp class="samp">\O4</samp>&rsquo;</dt>
+<dd><p>End a nested suppression level.
+</p></dd>
+</dl>
+
+<dl class="table">
+<dt>&lsquo;<samp class="samp">\O[5<var class="var">P</var><var class="var">file</var>]</samp>&rsquo;</dt>
+<dd><p>At the outermost suppression level, write the name <code class="code">file</code> to the
+standard error stream at position <var class="var">P</var>, which must be one of
+<code class="code">l</code>, <code class="code">r</code>, <code class="code">c</code>, or&nbsp;<code class="code">i</code>, corresponding to left,
+right, centered, and inline alignments within the document,
+respectively. <var class="var">file</var> is a name associated with the production of
+the next image.
+</p></dd>
+</dl>
+</dd></dl>
+
+<dl class="first-deffn">
+<dt class="deffn" id="index-_005cn_005b_002eO_005d"><span class="category-def">Register: </span><span><strong class="def-name"><code class="t">\n[.O]</code></strong><a class="copiable-link" href='#index-_005cn_005b_002eO_005d'> &para;</a></span></dt>
+<dd><a class="index-entry-id" id="index-_002eO"></a>
+<a class="index-entry-id" id="index-suppression-nesting-level-register"></a>
+<a class="index-entry-id" id="index-nesting-level_002c-suppression_002c-register"></a>
+<a class="index-entry-id" id="index-level_002c-suppression-nesting_002c-register"></a>
+<p>Output suppression nesting level applied by <code class="code">\O3</code> and <code class="code">\O4</code>
+escape sequences.
+</p></dd></dl>
+
+
+
+</div>
+<hr>
+<div class="nav-panel">
+<p>
+Next: <a href="Colors.html">Colors</a>, Previous: <a href="Environments.html">Environments</a>, Up: <a href="GNU-troff-Reference.html">GNU <code class="code">troff</code> Reference</a> &nbsp; [<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>
+
+
+
+</body>
+</html>