tex4ht updates, texhr r1096-1106

git-svn-id: svn://tug.org/texlive/trunk@62897 c570f23f-e606-0410-a88d-b1316a301751

7 files changed, 199 insertions, 70 deletions

diff --git a/Master/texmf-dist/source/generic/tex4ht/ChangeLog b/Master/texmf-dist/source/generic/tex4ht/ChangeLog
index c69257cad6e..8bd91f94e15 100644
--- a/Master/texmf-dist/source/generic/tex4ht/ChangeLog
+++ b/Master/texmf-dist/source/generic/tex4ht/ChangeLog
@@ -1,10 +1,60 @@
-2021-03-21  Michal Hoftich  <michal.h21@gmail.com>
+2022-04-04  Michal Hoftich  <michal.h21@gmail.com>
+
+	* tex4ht-4ht.tex (minted.4ht): fixed spurious whitespace produced by
+	\mintinline.
+	* tex4ht-html4.tex (html4.4ht): disable ht-fonts for inline Minted.
+
+2022-03-31  Michal Hoftich  <michal.h21@gmail.com>
+
+	* tex4ht-html4.tex (html4.4ht): support frames and background colors
+	in custom Listings environments.
+	https://tex.stackexchange.com/a/639135/2891
+
+2022-03-30  Michal Hoftich  <michal.h21@gmail.com>
+
+	* tex4ht-sty.tex (tex4ht.sty): don't redefine \IfFileExists. It can
+	break packages that don't expect extra tokens at it's end.
+	https://tex.stackexchange.com/a/638965/2891
+
+2022-03-29  Michal Hoftich  <michal.h21@gmail.com>
+
+	* tex4ht-4ht.tex (subfiles.4ht): fixed support for multiple included
+	files in the Subfiles package.
+	https://tex.stackexchange.com/a/353117/2891
+
+	* tex4ht-html4.tex (html4.4ht): handle \# character in \title.
+	https://tex.stackexchange.com/a/638821/2891
+
+2022-03-28  Michal Hoftich  <michal.h21@gmail.com>
+
+	* tex4ht-ooffice.tex (ooffice.4ht): don't use bold font for \textsf
+	command.
+
+2022-03-25  Michal Hoftich  <michal.h21@gmail.com>
+
+	* tex4ht-4ht.tex (biblatex.4ht): fixed issues with backref page
+	numbers.
+	https://github.com/michal-h21/make4ht/issues/58
+
+2022-03-24  Michal Hoftich  <michal.h21@gmail.com>
+
+	* tex4ht-mathjax.tex (mathjax-latex-4ht.4ht): use \detokenize to
+	prevent math environments from expansion.
+	https://puszcza.gnu.org.ua/bugs/?557
+	* tex4ht-4ht.tex (listings.4ht): ignore spurious spaces at beginning
+	of listings.
+	* tex4ht-html4.tex (html4.4ht): removed extra <br> tags, fixed
+	issues with extra newlines.
+	* tex4ht-4ht.tex (biblatex.4ht): removed spurious whitespace after
+	backrefences.
+
+2022-03-21  Michal Hoftich  <michal.h21@gmail.com>
 
 	* tex4ht-4ht.tex (arydshln.4ht): added basic support for the
 	Arydshln package.
 	https://tex.stackexchange.com/a/637897/2891
 
-2021-03-20  Michal Hoftich  <michal.h21@gmail.com>
+2022-03-20  Michal Hoftich  <michal.h21@gmail.com>
 
 	* tex4ht-4ht.tex (graphics.4ht): don't execute graphics rules when
 	user selected other driver than dvips.
@@ -13,13 +63,13 @@
 
 	* update-htfonts: add installed files, not dev.
 
-2021-03-20  Michal Hoftich  <michal.h21@gmail.com>
+2022-03-20  Michal Hoftich  <michal.h21@gmail.com>
 
 	* tex4ht-html4.tex (html4.4ht): added support for background and
 	border colors in Listings.
 	https://tex.stackexchange.com/a/637789/2891
 
-2021-03-17  Michal Hoftich  <michal.h21@gmail.com>
+2022-03-17  Michal Hoftich  <michal.h21@gmail.com>
 
 	* tex4ht-fonts-opensans.tex: added support for OpenSans fonts.
 	https://tex.stackexchange.com/q/637314/2891
diff --git a/Master/texmf-dist/source/generic/tex4ht/mktex4ht-cnf.tex b/Master/texmf-dist/source/generic/tex4ht/mktex4ht-cnf.tex
index 65fe3c18818..5a1bcfbba61 100644
--- a/Master/texmf-dist/source/generic/tex4ht/mktex4ht-cnf.tex
+++ b/Master/texmf-dist/source/generic/tex4ht/mktex4ht-cnf.tex
@@ -1,4 +1,4 @@
-% $Id: mktex4ht-cnf.tex 1095 2022-03-21 13:29:42Z michal_h21 $
+% $Id: mktex4ht-cnf.tex 1103 2022-03-29 15:46:43Z michal_h21 $
 % Manually-maintained file, listing *.4ht files created by tex4ht-4ht.tex.
 % Read by tex4ht-cond4ht.
 %
@@ -369,5 +369,6 @@
 \AddFile{9}{menukeys}
 \AddFile{9}{animate}
 \AddFile{9}{sectionbreak}
+\AddFile{9}{subfiles}
 \AddFile{9}{fontawesome5}
 % \AddFile{9}{mktex4ht}
diff --git a/Master/texmf-dist/source/generic/tex4ht/tex4ht-4ht.tex b/Master/texmf-dist/source/generic/tex4ht/tex4ht-4ht.tex
index b4ce6fa169f..c8020013b08 100644
--- a/Master/texmf-dist/source/generic/tex4ht/tex4ht-4ht.tex
+++ b/Master/texmf-dist/source/generic/tex4ht/tex4ht-4ht.tex
@@ -1,4 +1,4 @@
-% $Id: tex4ht-4ht.tex 1095 2022-03-21 13:29:42Z michal_h21 $
+% $Id: tex4ht-4ht.tex 1106 2022-04-04 10:06:26Z michal_h21 $
 % tex tex4ht-4ht   or   ht tex tex4ht-4ht
 %
 % Copyright 2009-2022 TeX Users Group    
@@ -2795,7 +2795,8 @@ Fix backlink support in BibLaTeX
     % insert link to the page
     \html:addr\Link-{}{|<haddr prefix|>\last:haddr}\EndLink%
     % save link to the .xref file
-    \Tag{)Q##1\thepage}{|<haddr prefix|>\last:haddr}%
+    % we need to use \protected@write to get correct page numbers in backrefs
+    \protected@write\:refout{}{\string\:CrossWord{)Q##1\thepage}{|<haddr prefix|>\last:haddr}{\folio}}
     % we need to save the link destination in .xref file
     % too, otherwise \Link command would issue warning
     \Tag{)Q|<haddr prefix|>\last:haddr}{\FileNumber}%
@@ -2823,18 +2824,18 @@ Fix backlink support in BibLaTeX
   % back to the citations on the given pages
   \let\orig:hyperlink\hyperlink%
   \let\hyperlink\bbx:hyperlink%
-  \ifnumless{\abx@pagerefstyle}{0}
+  \ifnumless{\abx@pagerefstyle}{0}%
     {\usebibmacro{list:plain}%
-     \ifhyperref
-       {\hyperlink{page.#1}{#1}}
-       {#1}}
-    {\ifnumequal{\value{listcount}}{1}
-       {\usebibmacro{pageref:init}}
+     \ifhyperref%
+       {\hyperlink{page.#1}{#1}}%
+       {#1}}%
+    {\ifnumequal{\value{listcount}}{1}%
+       {\usebibmacro{pageref:init}}%
        {}%
      \usebibmacro{pageref:comp}{#1}%
-     \ifnumequal{\value{listcount}}{\value{liststop}}
-       {\usebibmacro{pageref:dump}}
-       {}}
+     \ifnumequal{\value{listcount}}{\value{liststop}}%
+       {\usebibmacro{pageref:dump}}%
+       {}}%
   \let\hyperlink\orig:hyperlink%
 }
 
@@ -4745,6 +4746,43 @@ PDF mode, it is safest thing to do to just disable the package.
 \Hinput{sectionbreak}
 >>> \AddFile{9}{sectionbreak}
 
+
+\<subfiles.4ht\><<< 
+% subfiles.4ht (|version), generated from |jobname.tex 
+% Copyright 2022 TeX Users Group 
+|<TeX4ht license text|> 
+|<subfiles enddocument|>
+\Hinput{subfiles}
+\endinput
+>>> \AddFile{9}{subfiles}
+
+We use the original version of \Verb|\subfiles@renewEndDocument|, the only 
+change is that we added the \Verb|\choose:begin| redefinition. It is necessary
+to prevent processing of the document after \Verb|\end{document}| in the 
+included subfile.
+
+\<subfiles enddocument\><<<
+\def\:tempa#1{%
+  \ifcsname subfiles@end\endcsname
+  \else
+    \subfiles@saveEndTo\subfiles@end
+  \fi
+  \let\choose:begin\@secondoftwo
+  \expandafter\def\csname end \endcsname##1{%
+    \romannumeral
+    \subfiles@StrIfEqTF{##1}{document}{%
+      \z@
+      \subfiles@restoreEndFrom\subfiles@end
+      #1%
+    }{%
+      \expandafter\expandafter\expandafter\z@\subfiles@end{##1}%
+    }%
+  }%
+}
+
+\HLet\subfiles@renewEndDocument\:tempa
+>>>
+
 \Section{url.sty}
 %%%%%%%%%%%%%%%%%%
 
@@ -24776,22 +24814,44 @@ of LaTeX.  The \''\:gobbleII' is for getting rid of the
 
 \<minted.4ht\><<<
 % minted.4ht (|version), generated from |jobname.tex
-% Copyright 2020-2021 TeX Users Group
+% Copyright 2022 TeX Users Group
 |<TeX4ht license text|>
+
+|<minted inline fixes|>
+|<minted background color|>
+|<minted background color|>
+|<minted input fixes|>
+
+\Hinput{minted}
+\endinput
+>>> \AddFile{9}{minted}
+
+Support for inline Minted listings. We need to take care of
+newline and space characters, as they produce unwanted white space
+in the generated HTML.
+
+\<minted inline fixes\><<<
 \NewConfigure{InlineCode}{2}
+% this is a hack to hide a newline that is produced, and which causes spurious space in the output
+\NewConfigure{MintedHideNewline}{2} 
+\Configure{MintedHideNewline}{\HCode{<!--}}{\HCode{-->}}
 
 \def\:tempa#1{%
   \endgroup%
   \begingroup%
-  \Configure{BVerbatimInput}{\HCode{}}{}{}{}{}\a:InlineCode% The \HCode is necessary for correct paragraph handling
+  \Configure{BVerbatimInput}{\HCode{}\ht:special{t4ht@(}}% \HCode is necessary for correct paragraph handlingling
+  {\a:MintedHideNewline}{\ht:special{t4ht@)}}{}{}% also hide newline and spurious spaces
+  \a:InlineCode%
   \begingroup%
-  \o:minted@inline@iii:{#1}%
+  \o:minted@inline@iii:{#1}\b:MintedHideNewline%
   \b:InlineCode%
   \endgroup%
 }
 
 \HLet\minted@inline@iii\:tempa
+>>>
 
+\<minted background color\><<<
 % support for background color in Minted listings
 \NewConfigure{MintedColorbg}{2}
 \renewenvironment{minted@colorbg}[1]{%
@@ -24801,13 +24861,7 @@ of LaTeX.  The \''\:gobbleII' is for getting rid of the
   \a:MintedColorbg%
   }
   {\b:MintedColorbg\medskip\noindent}
-
-|<minted input fixes|>
-
-\Hinput{minted}
-\endinput
->>> \AddFile{9}{minted}
-
+>>>
 
 Minted sometimes produces unexpected results. For example, << characters 
 get translated to guilelemets. To prevent that, we define new configuration,
@@ -30938,19 +30992,21 @@ Configure list of listings
    \lst@newlinetrue
 }%
 \HLet\lst@NewLine\:tempa
-\def\lst@InputListing#1{% 
-    \begingroup 
-      \lsthk@PreSet \gdef\lst@intname{#1}% 
+\def\:tempa#1{
+    \begingroup%
+      \lsthk@PreSet\gdef\lst@intname{#1}% 
       \expandafter\lstset\expandafter{\lst@set}% 
-      \lsthk@DisplayStyle 
-      \catcode\active=\active 
-      \a:lstinputlisting \lst@Init\relax \let\lst@gobble\z@ 
-      \lst@SkipToFirst 
+      \lsthk@DisplayStyle%
+      \catcode\active=\active%
+      \a:lstinputlisting\special{t4ht@[}\lst@Init\relax \let\lst@gobble\z@%
+      \lst@SkipToFirst%
       \lst@ifprint \def\lst@next{\input{#1}}% 
-             \else \let\lst@next\@empty \fi 
-      \lst@next \lst@DeInit 
-      \b:lstinputlisting
+             \else \let\lst@next\@empty \fi%
+      \special{t4ht@]}\lst@next \lst@DeInit%
+      \b:lstinputlisting%
     \endgroup} 
+
+\HLet\lst@InputListing\:tempa 
 \NewConfigure{lstinputlisting}{2}
 >>>
 
diff --git a/Master/texmf-dist/source/generic/tex4ht/tex4ht-html4.tex b/Master/texmf-dist/source/generic/tex4ht/tex4ht-html4.tex
index f9edbd385b3..ba40def116e 100644
--- a/Master/texmf-dist/source/generic/tex4ht/tex4ht-html4.tex
+++ b/Master/texmf-dist/source/generic/tex4ht/tex4ht-html4.tex
@@ -1,4 +1,4 @@
-% $Id: tex4ht-html4.tex 1093 2022-03-20 16:15:35Z karl $
+% $Id: tex4ht-html4.tex 1106 2022-04-04 10:06:26Z michal_h21 $
 % Compile 4 times: latex tex4ht-html4
 % Copy html4.4ht into the work directory before all but the last compilation.
 %
@@ -6328,6 +6328,8 @@ thanks author date and>>>
 \def\mbox{\hbox}%
 \def\gobble:font##1##2{##2}\:TITLE: \no:fonts
 \def\footnotemark[##1]{}%
+\def\:hashintitle{\protect\symbol{35}}
+\let\#\:hashintitle
 \Tag{TITLE+}{\@title}}
 >>>
 
@@ -6352,6 +6354,8 @@ Old latex files need \verb'\no:fonts', but not new ones.---wrong, as far as writ
 \def\mbox{\hbox}%
 \def\gobble:font##1##2{##2}\:TITLE: \no:fonts
 \def\footnotemark[##1]{}%
+\def\:hashintitle{\protect\symbol{35}}
+\let\#\:hashintitle
 \Tag{TITLE+}{\shorttitle}}
 >>>
 
@@ -6378,6 +6382,8 @@ Old latex files need \verb'\no:fonts', but not new ones.---wrong, as far as writ
 \let \bf=\empty
 \let \centering=\empty
 \def \ignorespaces##1\vskip##2//{##1}%
+\def\:hashintitle{\protect\symbol{35}}
+\let\#\:hashintitle
 \Tag{TITLE+}{\@title//}%
 }%
 >>>
@@ -6391,6 +6397,8 @@ Old latex files need \verb'\no:fonts', but not new ones.---wrong, as far as writ
 \def\mbox{\hbox}%
 \let\\\space \def\TeX{TeX}%
 \def\gobble:font##1##2{##2}\:TITLE: \no:fonts
+\def\:hashintitle{\protect\symbol{35}}
+\let\#\:hashintitle
 \Tag{TITLE+}{\@title}}%
 >>>
 
@@ -12566,6 +12574,7 @@ y{\ht:special{t4ht@+\string&{35}x00FD{59}}y}%
 \<env for titles\><<<
 \let\"=\:same \let\~=\:same \let\^=\:same
 \let\v=\:same \let\'=\:same \let\r=\:same
+\let\#=\:same 
 \PictureOff
 >>>
 
@@ -15197,7 +15206,8 @@ listings.dtx.
 
 Configuration for the inline code
 \<configure html4 minted\><<<
-\Configure{InlineCode}{\HCode{<code>}}{\HCode{</code>}}
+\Configure{InlineCode}{\HCode{<code class="minted-inline">}\NoFonts}{\EndNoFonts\HCode{</code>}}
+\Css{code.minted-inline{font-family:monospace,monospace;}}
 >>>
 
 Configuration for listings with colored backgrounds
@@ -15236,21 +15246,29 @@ Inline listings snippets
    fixed size fonts (see listings.dtx)}
 >>>
 
+This configuration is used mainly when user defines new environment using \verb|lstnewenvironment|.
+
 \<configure html4 listings\><<<
+\HAssign\listingN=0
 \HAssign\listings:Depth = 0
 \Configure{listings}
-   {\ifvmode \IgnorePar\fi \EndP
+   {\ifvmode \IgnorePar\fi \EndP%
     {\everypar{}\leavevmode}\HCode{<!--l. \the\inputlineno-->}%
-     \ifnum \listings:Depth=0 \HCode{<pre class="listings">}\else
-                              \HCode{<span class="listings-nested">}\fi
-     \gHAdvance\listings:Depth by 1
+     \ifnum \listings:Depth=0 \HCode{<pre class="listings" id="listing-\listingN">}\else%
+                              \HCode{<span class="listings-nested" id="listing-\listingN">}\fi%
+     \gHAdvance\listings:Depth by 1%
+     \gdef\start:LstLn{}%
    }
    {\gHAdvance\listings:Depth by -1
     \ifnum \listings:Depth=0 \HCode{</pre>}\else
                              \HCode{</span>}\fi
    }
-   {|<nbsp|>\HCode{<br /><span class="label">}}
+   {\start:LstLn\HCode{<span class="label">}%
+   \gdef\start:LstLn{\HCode{\Hnewline}}}%
    {\HCode{</span>}}%
+\Css{pre.listings{font-family: monospace,monospace; white-space: pre-wrap; 
+                    margin-top:0.5em; margin-bottom:0.5em;
+                   }}
 >>>
 
 \<configure html4 listings\><<<
@@ -15280,14 +15298,12 @@ Inline listings snippets
 
 
 \<configure html4 listings\><<<
-\HAssign\listingN=0
 \ConfigureEnv{lstlisting}
    {\ifvmode \IgnorePar\fi \EndP  
-    \gHAdvance\listingN by 1
     \HCode{<!--l. \the\inputlineno-->}%
     \gdef\start:LstLn{%
        \HCode{<pre class="lstlisting" id="listing-\listingN">}%
-       \gdef\start:LstLn{|<nbsp|>\HCode{<br />\Hnewline}}}
+       \gdef\start:LstLn{\HCode{\Hnewline}}}
     \bgroup%
     % we put the closing </div> here in order to support floating listings
     % https://tex.stackexchange.com/a/615703/2891
@@ -15301,7 +15317,7 @@ Inline listings snippets
    {\egroup\par}
    {} {}
 \Css{.lstlisting .label{margin-right:0.5em; }}
-\Css{pre.lstlisting{font-family: monospace,monospace; white-space: nowrap; 
+\Css{pre.lstlisting{font-family: monospace,monospace; white-space: pre-wrap; 
                     margin-top:0.5em; margin-bottom:0.5em;
                    }}
 >>>
@@ -15310,14 +15326,12 @@ Inline listings snippets
 \Configure{lstinputlisting}  
    {\ifvmode \IgnorePar\fi \EndP  
     \HCode{<!--l. \the\inputlineno-->}%  
-    \gHAdvance\listingN by 1%
-    \HCode{<pre class="lstinputlisting" id="listing-\listingN">}%  
+    \gdef\start:LstLn{\HCode{<pre class="lstinputlisting" id="listing-\listingN">}\gdef\start:LstLn{\HCode{\Hnewline}}}% ignore first newline, to prevent spurious line
     \bgroup\ttfamily%\special{t4ht@(}%  
        \Configure{listings}%
          {{\everypar{}\leavevmode}}%  
          {{\everypar{}\leavevmode}}%  
-         {|<nbsp|>%
-             \HCode{<br />\Hnewline<span class="label">}}%  
+         {\start:LstLn\HCode{<span class="label">}}%  
          {\HCode{</span>}}%  
    }  
    {%\special{t4ht@)}
@@ -15325,7 +15339,7 @@ Inline listings snippets
     \ifvmode \IgnorePar\fi \EndP  \HCode{</pre>}\par}% 
 \Css{pre.lstinputlisting{
    font-family: monospace,monospace;
-   white-space: nowrap;
+   white-space: pre-wrap; 
 }}
 \Css{.lstinputlisting .label{margin-right:0.5em;}}
 >>>
@@ -15362,7 +15376,8 @@ Support for background and border color
 
 \<configure html4 listings\><<<
 \lst@AddToHook{Init}{%
-\bgroup%
+  \gHAdvance\listingN by 1% increase the ID before we save colors. 
+  \bgroup%
   % handle backround color and border in listings
   \ifx\lst@fillcolor\@empty\else%
     \lst@fillcolor%
diff --git a/Master/texmf-dist/source/generic/tex4ht/tex4ht-mathjax.tex b/Master/texmf-dist/source/generic/tex4ht/tex4ht-mathjax.tex
index 3c50d2cacf5..730a778fce7 100644
--- a/Master/texmf-dist/source/generic/tex4ht/tex4ht-mathjax.tex
+++ b/Master/texmf-dist/source/generic/tex4ht/tex4ht-mathjax.tex
@@ -1,4 +1,4 @@
-% $Id: tex4ht-mathjax.tex 1023 2021-12-02 09:42:42Z michal_h21 $
+% $Id: tex4ht-mathjax.tex 1098 2022-03-24 22:18:43Z michal_h21 $
 % compile: latex tex4ht-mathjax
 %
 % Copyright 2018-2021 TeX Users Group
@@ -104,7 +104,7 @@ verbatim to the HTML output.
 \newcommand\VerbMath[1]{%
   \cs_if_exist:cTF{#1}{
     \RenewDocumentEnvironment{#1}{+!b}{%
-      \NoFonts\expandafter\VerbMathToks\expandafter{##1}{#1}\EndNoFonts%
+      \NoFonts\expandafter\VerbMathToks\expandafter{\detokenize{##1}}{#1}\EndNoFonts%
     }{}
   }{}%
 }
diff --git a/Master/texmf-dist/source/generic/tex4ht/tex4ht-ooffice.tex b/Master/texmf-dist/source/generic/tex4ht/tex4ht-ooffice.tex
index 0395dadac0a..56de7c4c9c1 100644
--- a/Master/texmf-dist/source/generic/tex4ht/tex4ht-ooffice.tex
+++ b/Master/texmf-dist/source/generic/tex4ht/tex4ht-ooffice.tex
@@ -1,4 +1,4 @@
-% $Id: tex4ht-ooffice.tex 1074 2022-02-06 19:43:26Z michal_h21 $
+% $Id: tex4ht-ooffice.tex 1101 2022-03-28 11:52:50Z michal_h21 $
 % compile 3 times: latex tex4ht-ooffice
 %      htlatex tex4ht-ooffice "xhtml,4,sections+"
 %
@@ -7409,7 +7409,7 @@ The section style  can't be in style.xml?
 \<oo textsf style\><<<
 <style:style style:name="textsf" style:family="text">\Hnewline
    <style:text-properties fo:font-style="normal" 
-                     fo:font-weight="bold"
+                     fo:font-weight="normal"
                      style:font-family-generic="swiss" 
                      style:font-pitch="variable" />\Hnewline
 </style:style>\Hnewline
diff --git a/Master/texmf-dist/source/generic/tex4ht/tex4ht-sty.tex b/Master/texmf-dist/source/generic/tex4ht/tex4ht-sty.tex
index 6a5c7ed0e11..7bf410fe7a0 100644
--- a/Master/texmf-dist/source/generic/tex4ht/tex4ht-sty.tex
+++ b/Master/texmf-dist/source/generic/tex4ht/tex4ht-sty.tex
@@ -1,4 +1,4 @@
-% $Id: tex4ht-sty.tex 981 2021-09-14 20:14:03Z michal_h21 $
+% $Id: tex4ht-sty.tex 1104 2022-03-30 12:06:52Z michal_h21 $
 % tex tex4ht-sty   or   ht tex tex4ht-sty
 %
 % Copyright 2009-2020 TeX Users Group
@@ -9082,18 +9082,25 @@ and \`'\Configure{SUP}{ before }{ after }' get into effect.
 \<defs for early latex subs/sups\><<<
 \append:def\:RestoreCatcodes{\early:sub\early:sup}
 \let\:IfFileExists\IfFileExists
-\long\def\IfFileExists#1#2#3{%
-   \csname recall:sub\endcsname   
-   \csname recall:sup\endcsname
-   \expandafter\let\csname #1:sub\endcsname=\early:sub
-   \expandafter\let\csname #1:sup\endcsname=\early:sup
-   \let\early:sub=\relax     \let\recall:sub\relax   
-   \let\early:sup=\relax     \let\recall:sup\relax
-   \:IfFileExists{#1}{#2}{#3}%
-   \expandafter\let\expandafter\early:sub\csname #1:sub\endcsname
-   \expandafter\let\expandafter\early:sup\csname #1:sup\endcsname
-   \early:sub \early:sup
-}
+
+% I am not sure why we used this declaration. It is from the original 
+% TeX4ht sources, so it probably had some reason. The problem is that it 
+% inserts extra tokens after \:IfFileExists, and if some package uses
+% something like \IfFileExists{foo.sty}{\@firstoftwo}{\@secondoftwo}{aa}{bb}, 
+% then it fails. I've found this issue with the Standalone class.
+% See https://tex.stackexchange.com/a/638965/2891 for example where it fails.
+% \long\def\IfFileExists#1#2#3{%
+%    \csname recall:sub\endcsname   
+%    \csname recall:sup\endcsname
+%    \expandafter\let\csname #1:sub\endcsname=\early:sub
+%    \expandafter\let\csname #1:sup\endcsname=\early:sup
+%    \let\early:sub=\relax     \let\recall:sub\relax   
+%    \let\early:sup=\relax     \let\recall:sup\relax
+%    \:IfFileExists{#1}{#2}{#3}%
+%    \expandafter\let\expandafter\early:sub\csname #1:sub\endcsname
+%    \expandafter\let\expandafter\early:sup\csname #1:sup\endcsname
+%    \early:sub \early:sup
+% }
 \ifx \o:document\:UnDef
    \pend:def\Preamble{%
      \csname recall:sub\endcsname