Variable font support for LuaLaTeX

fontspec-code-internal.dtx

@@ -455,7 +455,7 @@
     \prop_gput:cnx {g_@@_fontinfo_ \g_@@_nfss_family_tl _prop} {fontdef}
       {
         \@@_construct_font_call:nn {\l_fontspec_fontname_tl}
-          { \l_@@_pre_feat_sclist \g_@@_rawfeatures_sclist }
+          { \l_@@_pre_feat_sclist \g_@@_rawfeatures_sclist \@@_get_variations: }
       }
     \prop_gput:cnV {g_@@_fontinfo_ \g_@@_nfss_family_tl _prop} {script-num} \l_@@_script_int
     \prop_gput:cnV {g_@@_fontinfo_ \g_@@_nfss_family_tl _prop} {lang-num}   \l_@@_language_int
@@ -800,7 +800,7 @@
 %<debug>\typeout{====~Setup~NFSS~shape:~<\l_@@_size_tl>~\l_fontspec_fontname_tl}
 
     \@@_get_features:n { #2 , #3 , #4 }
-%<debug>\typeout{====~Gathered~features:~\g_@@_rawfeatures_sclist}
+%<debug>\typeout{====~Gathered~features:~\g_@@_rawfeatures_sclist \@@_get_variations:}
 
     \tl_if_empty:NF \l_@@_scale_tl
       {
@@ -811,7 +811,7 @@
       {
         <\l_@@_size_tl> \l_@@_scale_tl
         \@@_construct_font_call:nn { \l_fontspec_fontname_tl }
-          { \l_@@_pre_feat_sclist \g_@@_rawfeatures_sclist }
+          { \l_@@_pre_feat_sclist \g_@@_rawfeatures_sclist \@@_get_variations: }
       }
   }
 %    \end{macrocode}
@@ -1062,6 +1062,33 @@
 %    \end{macrocode}
 % \end{macro}
 %
+% \begin{macro}{\@@_get_variations:}
+% \cmd{\@@_get_variations:} builds the feature string representing the
+% current variation instance and/or axis settings.
+%    \begin{macrocode}
+\cs_generate_variant:Nn \tl_tail:n { e }
+\cs_new:Nn \@@_format_axis:nn
+  {
+    , #1 = #2
+  }
+\cs_new:Nn \@@_get_variations:
+  {
+    \tl_if_empty:NF \g_@@_instance_tl
+      {
+        instance = { \g_@@_instance_tl };
+      }
+      \prop_if_empty:NF \g_@@_rawvariations_prop
+      {
+        axis = {
+          \tl_tail:e {
+            \prop_map_function:NN \g_@@_rawvariations_prop \@@_format_axis:nn
+          }
+        };
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
 % \subsection{Initialisation}
 %
 % \begin{macro}{\@@_init:}
@@ -1099,6 +1126,8 @@
 \cs_new:Nn \@@_init_fontface:
   {
     \tl_gclear:N \g_@@_rawfeatures_sclist
+    \prop_gclear:N \g_@@_rawvariations_prop
+    \tl_gclear:N \g_@@_instance_tl
     \tl_clear:N \l_@@_scale_tl
     \tl_set_eq:NN \l_@@_opacity_tl \c_@@_opacity_tl
     \tl_set_eq:NN \l_@@_hexcol_tl \c_@@_hexcol_tl

fontspec-code-keyval.dtx

@@ -782,14 +782,21 @@
 % \subsubsection{Continuous font axes}
 %
 %    \begin{macrocode}
+%<*XE>
 \@@_keys_define_code:nnn {fontspec} {Weight}
   {
     \@@_update_featstr:n{weight=#1}
   }
+%</XE>
+%<LU>\@@_define_opentype_variation_axis:nn {Weight} {wght}
+%<*XE>
 \@@_keys_define_code:nnn {fontspec} {Width}
   {
     \@@_update_featstr:n{width=#1}
   }
+%</XE>
+%<LU>\@@_define_opentype_variation_axis:nn {Width} {wdth}
+\@@_define_opentype_variation_axis:nn {Slant} {slnt}
 \@@_keys_define_code:nnn {fontspec} {OpticalSize}
 %<*XE>
   {
@@ -817,6 +824,23 @@
 %</LU>
 %    \end{macrocode}
 %
+% For other potentially font specific variation axes, there is a raw setter available:
+%    \begin{macrocode}
+\@@_keys_define_code:nnn {fontspec-opentype} {RawAxis}
+  {
+    \prop_gput_from_keyval:Nn \g_@@_rawvariations_prop {#1}
+  }
+%    \end{macrocode}
+%
+% \subsubsection{Variation instances}
+%
+%    \begin{macrocode}
+\@@_keys_define_code:nnn {fontspec-opentype} {Instance}
+  {
+    \tl_gset:Nn \g_@@_instance_tl {#1}
+  }
+%    \end{macrocode}
+%
 % \subsubsection{Font transformations}
 % These are to be specified to apply directly to a font shape:
 %    \begin{macrocode}

fontspec-code-opentype.dtx

@@ -10,6 +10,22 @@
 %
 %
 %
+% \begin{macro}{\@@_define_opentype_variation_axis:nn}
+%    \begin{macrocode}
+\cs_new:Nn \@@_define_opentype_variation_axis:nn
+  {
+    \keys_define:nn {fontspec-opentype}
+      {
+        #1 .code:n = {
+          \prop_gput:Nnn \g_@@_rawvariations_prop { #2 } { ##1 }
+        },
+        #1 .value_required:n = true,
+        #1 .groups:n = {opentype},
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
 % \begin{macro}{\@@_define_opentype_feature_group:n}
 %    \begin{macrocode}
 \cs_new:Nn \@@_define_opentype_feature_group:n

fontspec-code-vars.dtx

@@ -152,6 +152,7 @@
 \prop_new:N \g_@@_strong_prop
 \prop_new:N \g_@@_fontid_family_prop
 \prop_new:N \g_@@_family_int_prop
+\prop_new:N \g_@@_rawvariations_prop
 %    \end{macrocode}
 %
 % \paragraph{Token lists}
@@ -289,6 +290,7 @@
 \tl_new:N \l_@@_punctspace_adjust_tl
 \tl_new:N \l_@@_wordspace_adjust_tl
 \tl_new:N \l_@@_postadjust_tl
+\tl_new:N \g_@@_instance_tl
 %    \end{macrocode}
 %
 %    \begin{macrocode}

fontspec-doc-featset.tex

@@ -608,6 +608,90 @@ \subsection{Letter spacing}
 In particular, small amounts of letter spacing can be very useful, when setting small caps or all caps titles.
 Also see the OpenType \opt{Uppercase} option of the \feat{Letters} feature (\vref{sec:letters}).
 
+
+\section{Variable fonts} \label{sec:variable}
+
+OpenType variable fonts and Multiple Master fonts are parameterised over
+orthogonal font axes, allowing continuous selection along such features
+as weight, width, and optical size.
+
+Currently OpenType variable fonts are only supported in \LuaTeX, while
+Multiple Master fonts only work with \XeTeX.
+
+\subsection{Optical font sizes} \label{sec:aat-opticalsize}
+Whereas traditional OpenType fonts will have only a few separate
+optical sizes, a Variable or Multiple Master font's optical size can be
+specified over a continuous range. Unfortunately, this flexibility makes
+it harder to create an automatic interface through \LaTeX, and the
+optical size for a Variable or Multiple Master font must always be specified
+explicitly.
+\begin{Verbatim}
+  \fontspec{Minion MM Roman}[OpticalSize=11]
+   MM optical size test                    \\
+  \fontspec{Minion MM Roman}[OpticalSize=47]
+   MM optical size test                    \\
+  \fontspec{Minion MM Roman}[OpticalSize=71]
+   MM optical size test                    \\
+\end{Verbatim}
+
+
+\subsection{Weight} \label{sec:variable-weight}
+For fonts with a variable weight axis, the weight can be specified through the
+\feat{Weight} feature. The value should be between 0 and 1000, where typically
+400 corresponds to regular wight and 700 is a bold font.
+\begin{Verbatim}
+  \fontspec{Source Serif Variable}[Weight=700]
+  Bold                                     \\
+  \fontspec{Source Serif Variable}[Weight=200]
+  Extra Light                              \\
+\end{Verbatim}
+
+
+\subsection{Width} \label{sec:variable-width}
+Similarly, the \feat{Width} feature allows specifying the value of the width axis,
+where the value is a percentage of normal width.
+\begin{Verbatim}
+  \fontspec{Noto Serif}[Width=100]
+  Normal Width                             \\
+  \fontspec{Noto Serif}[Width=75]
+  Condensed                                \\
+\end{Verbatim}
+
+\subsection{Slant} \label{sec:variable-slant}
+Also fonts with a slant axis can be controlled with the \feat{Slant} feature.
+In a standard compliant font the value should specify the clockwise angle in degree
+the glyphs are slanted. Therefore for a typical forward leaning slanted font, a
+negative value should be passed.
+
+Many fonts use this feature in non-standard ways, so you might have to experiment
+a bit with the value.
+\begin{Verbatim}
+  \fontspec{Roboto Flex}[Slant=0]
+  Upright                            \\
+  \fontspec{Roboto Flex}[Slant=-5]
+  Slanted                            \\
+\end{Verbatim}
+
+\subsection{Other axes} \label{sec:variable-raw}
+For OpenType variable fonts, additional axis values can be specified
+if the four letter tag of these axes is known.
+Than their value can be set with the \feat{RawAxis} feature:
+\begin{Verbatim}
+  \fontspec{Noto Serif}[RawAxis={CTGR=100}]
+  Maximal contrast                        \\
+  \fontspec{Noto Serif}[RawAxis={CTGR=0}]
+  Regular contrast                        \\
+\end{Verbatim}
+
+\subsection{Instances} \label{sec:variable-instances}
+Instead of manually setting axis values, many fonts contain named instances which are predefined settings of all axes.
+
+To select such an instance, the \feat{Instance} feature can be used:
+\begin{Verbatim}
+  \fontspec{Noto Serif}[Instance=ExtraCondensed Bold]
+  This is in extra condensed bold.
+\end{Verbatim}
+
 \end{document}
 
 % /©

fontspec-doc-xetex.tex

@@ -58,27 +58,6 @@ \subsection{Different font technologies: \AAT, OpenType, and Graphite}\label{sec
 select the \opt{OpenType} renderer.}
 
 
-\subsection{Optical font sizes} \label{sec:aat-opticalsize}
-
-Multiple Master fonts are parameterised over
-orthogonal font axes, allowing continuous selection along such
-features as weight, width, and optical size.
-Whereas an OpenType font will have only a few separate
-optical sizes, a Multiple Master font's optical size can be
-specified over a continuous range. Unfortunately, this flexibility makes
-it harder to create an automatic interface through \LaTeX, and the
-optical size for a Multiple Master font must always be specified
-explicitly.
-\begin{Verbatim}
-  \fontspec{Minion MM Roman}[OpticalSize=11]
-   MM optical size test                    \\
-  \fontspec{Minion MM Roman}[OpticalSize=47]
-   MM optical size test                    \\
-  \fontspec{Minion MM Roman}[OpticalSize=71]
-   MM optical size test                    \\
-\end{Verbatim}
-
-
 \subsection{Vertical typesetting}
 
 \XeTeX\ provides for vertical typesetting simply with the ability to rotate

testfiles/fontload-variable.luatex.tlg

@@ -0,0 +1,9 @@
+This is a generated file for the l3build validation system.
+Don't change this file in any respect.
+Default: 9.45pt
+Bold: 9.86pt
+Black: 10.16pt
+Black condensed: 8.98pt
+Extracondensed Bold: 8.07pt
+***************
+Compilation 1 of test file completed with exit status 0

testfiles/fontload-variable.lvt

@@ -0,0 +1,33 @@
+\input{fontspec-testsetup.tex}
+
+\usepackage{fontspec}
+\usepackage{iftex}
+\ifluahbtex
+  \defaultfontfeatures{Renderer=HarfBuzz}
+\fi
+
+\begin{document}
+
+\START
+
+\fontspec{NotoSerif-VF.ttf}
+\setbox0\hbox{m}
+\MSG{Default: \the\wd0}
+
+\fontspec[Weight=700]{NotoSerif-VF.ttf}
+\setbox0\hbox{m}
+\MSG{Bold: \the\wd0}
+
+\fontspec[Weight=900]{NotoSerif-VF.ttf}
+\setbox0\hbox{m}
+\MSG{Black: \the\wd0}
+
+\fontspec[Weight=900, Width=75]{NotoSerif-VF.ttf}
+\setbox0\hbox{m}
+\MSG{Black condensed: \the\wd0}
+
+\fontspec[Instance=ExtraCondensed Bold]{NotoSerif-VF.ttf}
+\setbox0\hbox{m}
+\MSG{Extracondensed Bold: \the\wd0}
+
+\end{document}

testfiles/fontload-variable.xetex.tlg

@@ -0,0 +1,9 @@
+This is a generated file for the l3build validation system.
+Don't change this file in any respect.
+Default: 9.45pt
+Bold: 9.45pt
+Black: 9.45pt
+Black condensed: 9.45pt
+Extracondensed Bold: 9.45pt
+***************
+Compilation 1 of test file completed with exit status 0