<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Thanks for inquiry.<div class=""><br class=""></div><div class="">About:</div><div class=""><br class=""><div><blockquote type="cite" class=""><div class=""><div class=""><br class="">I welcome counterexamples, but I see no practical use for it. And there<br class="">don't seem to be any real-world documents in the TeX universe using it. -k<br class=""><br class=""></div></div></blockquote><br class=""></div></div><div>The Python Sphinx documentation generator (<a href="https://www.sphinx-doc.org" class="">https://www.sphinx-doc.org</a>)</div><div>uses it. Most users target HTML/CSS hence often use "px" unit for</div><div>image inclusion. From the sources of the user projects, Sphinx</div><div>produces output in HTML/CSS</div><div>or also other formats including PDF via LaTeX. Hence availability of px unit</div><div>in pdfTeX and luaTeX allows to interpret the user input directly.</div><div><br class=""></div><div>Arbitrarily \pdfpxdimen=0.75bp is issued by default to obtain circa 96px to 1in.</div><div><br class=""></div><div>As Sphinx user may use also xelatex or platex, Sphinx LaTeX writer</div><div>actually does not use "px"</div><div>in output markup but a custom \dimen register. On pdfTeX it is let to \pdfpxdimen</div><div>on luaTeX it is let to \pxdimen on other engines it is allocated as new \dimen.</div><div><br class=""></div><div>Then user input "xyz.abcd px" becomes "xyz.abcd \sphinxpxdimen" in LaTeX mark-up.</div><div><br class=""></div><div>On pdfTeX/LuaTeX, this is totally equivalent to using "px" unit, </div><div>due to the Knuth rules for parsing dimensional inputs.</div><div>(and the way the engines themselves interpret "px" as being</div><div>associated with an N/65536 ratio factor)</div><div><br class=""></div><div>So, if the feature was to be dropped from engines, Sphinx would be robust</div><div>against such change (it uses \ifdefined to check, not an engine check).</div><div><br class=""></div><div>Sorry for verbose, but I felt I had to explain that real-world documents</div><div>do use it... but it is "expendable" indeed.</div><div><br class=""></div><div>Best,</div><div><br class=""></div><div>Jean-François</div><div><br class=""></div><div><br class=""></div></body></html>