DOC: remove old LaTeX hack if Sphinx is at 5.0.0 or later (fix #22941) (

#22952)

This removes an old LaTeX hack if Sphinx is at 5.0.0+. The hack served to insert a newline after each parameter name before its description and is unneeded as Sphinx 5+ does it (otherwise) and it now causes extra vertical whitespace.

If one day in future NumPy pins Sphinx to be at least 5.0.0, the whole thing will become removable.

Closes #22941

EDIT: this also removes \usepackage{xcolor}. Sphinx for many many years uses xcolor if it is available.

doc/source/conf.py

@@ -253,26 +253,31 @@ def setup(app):
 # Additional stuff for the LaTeX preamble.
 latex_elements['preamble'] = r'''
 % In the parameters section, place a newline after the Parameters
-% header
-\usepackage{xcolor}
+% header.  This is default with Sphinx 5.0.0+, so no need for
+% the old hack then.
+% Unfortunately sphinx.sty 5.0.0 did not bump its version date
+% so we check rather sphinxpackagefootnote.sty (which exists
+% since Sphinx 4.0.0).
+\makeatletter
+\@ifpackagelater{sphinxpackagefootnote}{2022/02/12}
+    {}% Sphinx >= 5.0.0, nothing to do
+    {%
 \usepackage{expdlist}
 \let\latexdescription=\description
 \def\description{\latexdescription{}{} \breaklabel}
 % but expdlist old LaTeX package requires fixes:
 % 1) remove extra space
 \usepackage{etoolbox}
-\makeatletter
 \patchcmd\@item{{\@breaklabel} }{{\@breaklabel}}{}{}
-\makeatother
 % 2) fix bug in expdlist's way of breaking the line after long item label
-\makeatletter
 \def\breaklabel{%
     \def\@breaklabel{%
         \leavevmode\par
         % now a hack because Sphinx inserts \leavevmode after term node
         \def\leavevmode{\def\leavevmode{\unhbox\voidb@x}}%
     }%
 }
+    }% Sphinx < 5.0.0 (and assumed >= 4.0.0)
 \makeatother
 
 % Make Examples/etc section headers smaller and more compact