LuaLatex font discrepancies and compilation speed with fontspec

Question

Making a transition from XeLatex to LuaLatex and I'm struggling with some odd font and loading issues.

My starting point for this question is this answer by https://tex.stackexchange.com/a/234785/15886 by @ulrike-fischer - 5 years ago. 5 years later and using a current version of TexLive and LuaHBTeX, Version 1.12.0 (TeX Live 2020/W32TeX) (format=lualatex 2020.7.28) on Windows 10

I am getting quite slow compilation speeds versus XeLatex

Like Ulrike I find that supposedly switching off the "feature" of fontspec to search for .fontspec files massively speeds compilation by a factor of 3 (for example from 23 seconds to 8 seconds on my current document)

I start with Ulrike's MWE (below) extended to add some font testing routines.

Lines 4--7 of the MWE according to Ulricke do nothing more than prevent an unnecessary search for .fontspec files. This should make no difference to the output of the MWE anyway, because the fonts in the libertine package used here do not seem to have .fontspec files anyway.

Toggling lines 4-7 on/off does indeed massively speed compilation (not demonstrable with this short MWE so clearly not just to do with initial font loading). However the fonts are actually changed, for reasons I don't understand.

The last few lines of the MWE output are for example - without Ulrike's magic lines

and with Ulrike's lines (which supposedly just switch off .fontspec search

So my questions are:

a) Why does preventing the system-killing search for .fontspec change the rendering, particularly when libertine does not use this anyway b) 5 years after the earlier question, what should we be doing in LuaLatex in terms of font loading. If I want to use libertine and Biolinium for example should I be loading them from a package (supposedly LuaLatex "compliant") or directly, with fontspec at all (?), and how should I be dealing with this slowing - which is clearly something to do with fonts, perhaps only on Windows?

MWE Follows:

\documentclass{article}
\usepackage{fontspec}
\usepackage{booktabs}
 % \ExplSyntaxOn
 % \cs_set:Nn \__fontspec_load_external_fontoptions:Nn
 %  {}
 % \ExplSyntaxOff
\usepackage{libertine}

\begin{document}
\newcommand{\FontCmd}[3]{\PBS\verb!\#1{!\textit{text}\verb!}!  \> %
                         \verb!{\#2 !\textit{text}\verb!}! \> %
                         \#1{#3}}
\begin{tabular}{lll}
\textit{Command} & \textit{Declaration} & \textit{Effect} \\
\verb!\textrm{!\textit{text}\verb!}!                    & %
        \verb!{\rmfamily !\textit{text}\verb!}!               & %
        \textrm{Roman family} \\
\verb!\textsf{!\textit{text}\verb!}!                    & %
        \verb!{\sffamily !\textit{text}\verb!}!               & %
        \textsf{Sans serif family} \\
\verb!\texttt{!\textit{text}\verb!}!                    & %
        \verb!{\ttfamily !\textit{text}\verb!}!               & %
        \texttt{Typewriter family} \\
\verb!\textmd{!\textit{text}\verb!}!                    & %
        \verb!{\mdseries !\textit{text}\verb!}!               & %
        \textmd{Medium series} \\
\verb!\textbf{!\textit{text}\verb!}!                    & %
        \verb!{\bfseries !\textit{text}\verb!}!               & %
        \textbf{Bold series} \\
\verb!\textup{!\textit{text}\verb!}!                    & %
        \verb!{\upshape !\textit{text}\verb!}!               & %
        \textup{Upright shape} \\
\verb!\textit{!\textit{text}\verb!}!                    & %
        \verb!{\itshape !\textit{text}\verb!}!               & %
        \textit{Italic shape} \\
\verb!\textsl{!\textit{text}\verb!}!                    & %
        \verb!{\slshape !\textit{text}\verb!}!               & %
        \textsl{Slanted shape} \\
\verb!\textsc{!\textit{text}\verb!}!                    & %
        \verb!{\scshape !\textit{text}\verb!}!               & %
        \textsc{Small Caps shape} \\
\verb!\emph{!\textit{text}\verb!}!                      & %
        \verb!{\em !\textit{text}\verb!}!               & %
        \emph{Emphasized} \\
\verb!\textnormal{!\textit{text}\verb!}!                & %
        \verb!{\normalfont !\textit{text}\verb!}!       & %
        \textnormal{Document font} \\
\verb!\underline{!\textit{text}\verb!}!                 & %
                                                        & %
        \underline{Underline}
\end{tabular}

\begin{tabbing}
\verb!\footnotesizezzz!          \= \kill%sets the tab
\verb!\tiny!                  \>  \tiny{tiny} \\
\verb!\scriptsize!            \>  \scriptsize{scriptsize} \\
\verb!\footnotesize!          \>  \footnotesize{footnotesize} \\
\verb!\small!                 \>  \small{small} \\
\verb!\normalsize!            \>  \normalsize{normalsize} \\
\verb!\large!                 \>  \large{large} \\
\verb!\Large!                 \>  \Large{Large} \\
\verb!\LARGE!                 \>  \LARGE{LARGE} \\
\verb!\huge!                  \>  \huge{huge} \\
\verb!\Huge!                  \>  \Huge{Huge}
\end{tabbing}

\begin{tabular}{@{}ll@{}}
\textit{Environment}  &  \textit{Declaration}  \\
\verb!\begin{center}!      & \verb!\centering!  \\
\verb!\begin{flushleft}!  & \verb!\raggedright! \\
\verb!\begin{flushright}! & \verb!\raggedleft!  \\
\end{tabular}

\begin{tabular}{@{}llll@{}}
\textit{Name} & \textit{Source} & \textit{Example} & \textit{Usage} \\
hyphen  & \verb!-!   & X-ray          & In words. \\
en-dash & \verb!--!  & 1--5           & Between numbers. \\
em-dash & \verb!---! & Yes---or no?    & Punctuation.
\end{tabular}

\textasciitilde

\textasciicircum

\textbackslash

\begin{tabular}{ll}\toprule
\textbf{x} & \textbf{y} \\\midrule
    \verb|`|&`\\
    \verb|'|&'\\
    \verb|``|&``\\
    \verb|''|&''\\
    \verb|"|&"\\
    \verb|,,|&,,\\
    \verb|<<|&<<\\
    \verb|>>|&>>\\
    \verb|--|&--\\
    \verb|---|&---\\
\bottomrule
\end{tabular}

\verb|{\Huge\libertineGlyph{uni211A}}| \hfill {\Huge\libertineGlyph{uni211A}} \par\medskip
\verb|{\Huge\libertineGlyph{uni211A}}| \hfill {\Huge\libertineGlyph{uni211A}} \par\medskip
\verb|{\Huge\textbf{\libertineGlyph{uni211A}}}| \hfill{\Huge\textbf{\libertineGlyph{uni211A}}} \par\medskip
\verb|{\Huge\textit{\libertineGlyph{uni211A}}}| \hfill {\Huge\textit{\libertineGlyph{uni211A}}} \par\medskip

\begin{tabbing}
\verb!\footnotesizezzz!          \= \kill
\verb!\tiny!                  \>  {\tiny tiny} \\
\verb!\scriptsize!            \>  {\scriptsize scriptsize} \\
\verb!\footnotesize!          \>  {\footnotesize footnotesize} \\
\verb!\small!                 \>  {\small small} \\
\verb!\normalsize!            \>  {\normalsize normalsize} \\
\verb!\large!                 \>  {\large large} \\
\verb!\Large!                 \>  {\Large Large} \\
\verb!\LARGE!                 \>  {\LARGE LARGE } \\
\verb!\huge!                  \>  {\huge huge} \\
\verb!\Huge!                  \>  {\Huge Huge}\\
\end{tabbing}

\par{\Huge\textit{textit text test}}
\bigskip
\par{\sffamily\bfseries\Huge Test Text}

\end{document}

Answer 1

(This is more of a comment than an answer, but it was too long for that...)

Ulrike's

\ExplSyntaxOn
\cs_set:Nn \__fontspec_load_external_fontoptions:Nn
 {}
\ExplSyntaxOff

should no longer be used for modern fontspec versions since fontspec added an official interface for this: The IgnoreFontspecFile option. Basically any font loaded with this option will not trigger a search for a fontspec file. When using the libertine package and not loading the fonts directly, you can pass this option using libertines defaultfeatures option:

\usepackage[defaultfeatures=IgnoreFontspecFile]{libertine}

This still shows the issue you observed though. This is a fontspec bug but the fix will probably be merged soon.

I guess that this won't fix your issue either because you mentioned that the delay does not appear during font loading but later in the document. In that case it's probably not caused by searching the fontspec file at all and the speedup after this change appeared as a sideeffect of using less fonts because of the bug. Of course it's hard to say without seeing an example file which shows the slowdown.

Answer 2

I’m not sure why this problem would be reappearing five years after Ulrike Fischer reported that the bug in file search was fixed. This might be a regression.

I’ve noticed (in TeX Live 2020) that LuaLaTeX sometimes takes an excessive amount of time and memory to load large fonts, unless I specify Renderer=HarfBuzz.

In theory, fontspec should not need to search for as many filenames if you specify UprightFont=, BoldFont=, ItalicFont=, BoldItalicFont=, and Extension=, or search at all if you also specify Path=.

Answer 3

I don't know why but moving the \usepackage{libertine} line before the ExplSyntax lines seems to avoid the problem.