lfs-book/stylesheets/lfs-xsl/docbook-xsl-1.78.1/params/nominal.image.width.xml

<refentry xmlns="http://docbook.org/ns/docbook"
          xmlns:xlink="http://www.w3.org/1999/xlink"
          xmlns:xi="http://www.w3.org/2001/XInclude"
          xmlns:src="http://nwalsh.com/xmlns/litprog/fragment"
          xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
          version="5.0" xml:id="nominal.image.width">
<refmeta>
<refentrytitle>nominal.image.width</refentrytitle>
<refmiscinfo class="other" otherclass="datatype">length</refmiscinfo>
</refmeta>
<refnamediv>
<refname>nominal.image.width</refname>
<refpurpose>The nominal image width</refpurpose>
</refnamediv>

<refsynopsisdiv>
<src:fragment xml:id="nominal.image.width.frag">
<xsl:param name="nominal.image.width" select="6 * $pixels.per.inch"/>
</src:fragment>
</refsynopsisdiv>

<refsection><info><title>Description</title></info>

<para>Graphic widths expressed as a percentage are problematic. In the
following discussion, we speak of width and contentwidth, but
the same issues apply to depth and contentdepth.</para>

<para>A width of 50% means "half of the available space for the image."
That's fine. But note that in HTML, this is a dynamic property and
the image size will vary if the browser window is resized.</para>

<para>A contentwidth of 50% means "half of the actual image width".
But what does that mean if the stylesheets cannot assess the image's
actual size? Treating this as a width of 50% is one possibility, but
it produces behavior (dynamic scaling) that seems entirely out of
character with the meaning.</para>

<para>Instead, the stylesheets define a
<parameter>nominal.image.width</parameter> and convert percentages to
actual values based on that nominal size.</para>

</refsection>
</refentry>