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+%% This is part of the OpTeX project, see http://petr.olsak.net/optex
+
+\_codedecl \fontfam {Fonts selection system <2021-02-25>} % preloaded in format
+
+ \_doc -----------------------------
+ \`\initunifonts` macro extends \LuaTeX's font capabalities,
+ in order to be able to load Unicode fonts. Unfortunately, this part of
+ \OpTeX/ depends on `luaotfload` package, which adapts Con\TeX/t's generic
+ font loader for plain \TeX/ and \LaTeX. `luaotfload` uses Lua functions
+ from \LaTeX's `luatexbase` namespace, we provide our own replacements.
+ Moreover, `\initunifont` switches with
+ the \^`\_doresizefont` macro to OTF mode which is represented by the
+ macro \`\_doresizeunifont`. This mode includes
+ a fallback to TFM mode if \^`\_fontnamegen` is not defined.
+ Finally, `\initunifonts` sets itself to relax because we don't want to do
+ this work twice.\nl
+ \`\_ttunifont` is default font for `\tt` variant if
+ `f-lmfonts.opm` (or another font file where `\tt` is declared) is not loaded.
+ \_cod -----------------------------
+
+\_def\_initunifonts {%
+ \directlua{%
+ require('luaotfload-main')
+ luaotfload.main()
+ }%
+ \_gdef\_rfskipatX ##1" ##2\_relax{"##1"}%
+ \_global\_let \_doresizefont=\_doresizeunifont
+ \_gdef\_tryloadtt {\_fontdef\_tentt{\_let\_fontnamegen=\_ttunifont\_rm}}%
+ \_global\_let \_initunifonts=\_relax % we need not to do this work twice
+ \_global\_let \initunifonts=\_relax
+}
+\_gdef\_doresizeunifont #1{\_logfont{#1}%
+ \_ifx\_fontnamegen\_undefined \_doresizetfmfont#1\_else
+ \_font#1={\_fontnamegen} \_sizespec \_relax \_setwsp#1\_relax
+ \_fi
+}
+\_def\_ttunifont{[lmmono10-regular]:\_fontfeatures-tlig;}
+
+\_public \initunifonts ;
+
+ \_doc -----------------------------
+ The \`\_famdecl` `[<Family Name>] \<Famselector> {<comment>} {<modifiers>} {<variants>} {<math>}`\nl
+ `{<font for testing>} {\def`\^`\_fontnamegen``{<data>}}` runs \^`\initunifonts`, then
+ checks if `\<Famselector>` is defined. If it is true, then closes the file by
+ `\endinput`. Else it defines `\<Famselector>` and saves it to the
+ internal `\_f:<currfamily>:main.fam` command.
+ The macro \`\_initfontfamily` needs it. The \`\_currfamily` is set
+ to the `<Famselector>` because the following \^`\moddef` commands need to
+ be in the right font family context. The `\_currfamily` is set to the
+ `<Famselector>` by the `\<Famselector>` too, because `\<Famselector>`
+ must set the right font family context. The font family context is given by the current
+ `\_currfamily` value and by the actual meaning of the \^`\_fontnamegen` macro.
+ The \`\_mathfaminfo` is saved for usage in the catalog.
+ \_cod -----------------------------
+
+\_def\_famdecl [#1]#2#3#4#5#6#7#8{%
+ \_initunifonts \_uniaccents
+ \_unless\_ifcsname _f:\_csstring#2:main.fam\_endcsname
+ \_isfont{#7}\_iffalse
+ \_opwarning{Family [#1] skipped, font "#7" not found}\_ea\_ea\_ea\_endinput \_else
+ \_edef\_currfamily {\_csstring #2}\_def\_mathfaminfo{#6}%
+ \_wterm {FONT: [#1] -- \_string#2 \_detokenize{(#3)^^J mods:{#4} vars:{#5} math:{#6}}}%
+ \_unless \_ifx #2\_undefined
+ \_opwarning{\_string#2 is redefined by \_string\_famdecl\_space[#1]}\_fi
+ \_protected\_edef#2{\_def\_noexpand\_currfamily{\_csstring #2}\_unexpanded{#8\_resetfam}}%
+ \_ea \_let \_csname _f:\_currfamily:main.fam\_endcsname =#2%
+ \_fi
+ \_else \_csname _f:\_csstring#2:main.fam\_endcsname \_reloading \_rm \_ea \_endinput \_fi
+}
+\_def\_initfontfamily{%
+ \_csname _f:\_currfamily:main.fam\_endcsname \_reloading \_rm
+}
+
+ \_doc -----------------------------
+ \`\_regoptsizes` `<internal-template> <left-output>?<right-output> <resizing-data>`
+ prepares data for using by the \`\_optname` `<internal-template>` macro.
+ The data are saved to the `\_oz:<internal-template>` macro.
+ When the `\_optname` is expanded then the data are scanned by the macro
+ \`\_optnameA` `<left-output>?<right-output> <mid-output> `\code{<}`<size>`
+ in the loop.\nl
+ \`\_optfontalias` `{<template A>}{<template B>}` is defined as
+ `\let\_oz:<templateA>=\_oz:<templateB>`.
+ \_cod -----------------------------
+
+\_def\_regoptsizes #1 #2?#3 #4*{\_sdef{_oz:#1}{#2?#3 #4* }}
+\_def\_optname #1{\_ifcsname _oz:#1\_endcsname
+ \_ea\_ea\_ea \_optnameA \_csname _oz:#1\_ea\_endcsname
+ \_else \_failedoptname{#1}\_fi
+}
+\_def\_failedoptname #1{optname-fails:(#1)}
+\_def\_optnameA #1?#2 #3 <#4 {\_ifx*#4#1#3#2\_else
+ \_ifdim\_optsize<#4pt #1#3#2\_optnameC
+ \_else \_afterfifi \_optnameA #1?#2 \_fi\_fi
+}
+\_def\_optnameC #1* {\_fi\_fi}
+\_def\_afterfifi #1\_fi\_fi{\_fi\_fi #1}
+\_def\_optfontalias #1#2{\_slet{_oz:#1}{_oz:#2}}
+
+ \_doc -----------------------------
+ \`\_fvars` `<rm-template> <bf-template> <it-template> <bi-template>`
+ saves data for usage by the `\_currV` macro. If a template is only dot
+ then previous template is used (it can be used if the font family doesn't
+ dispose with all standard variants).
+ \nl
+ \`\_currV` expands to a template declared by `\_fvars` depending on the
+ `<variant name>`. Usable only of standard four variants. Next variants
+ can be declared by the \^`\famvardef` macro.
+ \nl
+ \`\_fsetV` `<key>=<value>,...,<key>=<value>` expands to
+ `\def\_<key>V{<value>}` in the loop.
+ \nl
+ \`\_onlyif` `<key>=<value-a>,<value-b>...,<value-z>: {<what>}`
+ runs <what> only if the `\_<key>V` is defined as `<value-a>` or
+ `<value-b>` or ... or `<value-z>`.
+ \nl
+ \`\_prepcommalist` `ab,{},cd,\_end,` expands to `ab,,cd,` (auxiliary macro
+ used in `\_onlyif`).
+ \_cod -----------------------------
+
+\_def\_fvars #1 #2 #3 #4 {%
+ \_sdef{_fvar:rm}{#1}%
+ \_sdef{_fvar:bf}{#2}%
+ \_ifx.#2\_slet{_fvar:bf}{_fvar:rm}\_fi
+ \_sdef{_fvar:it}{#3}%
+ \_ifx.#3\_slet{_fvar:it}{_fvar:rm}\_fi
+ \_sdef{_fvar:bi}{#4}%
+ \_ifx.#4\_slet{_fvar:bi}{_fvar:it}\_fi
+}
+\_def\_currV{\_cs{_fvar:\_whatresize}}
+\_def\_V{ }
+\_def \_fsetV #1 {\_fsetVa #1,=,}
+\_def \_fsetVa #1=#2,{\_isempty{#1}\_iffalse
+ \_ifx,#1\_else\_sdef{_#1V}{#2}\_ea\_ea\_ea\_fsetVa\_fi\_fi
+}
+\_def \_onlyif #1=#2:#3{%
+ \_edef\_act{\_noexpand\_isinlist{,\_prepcommalist #2,\_end,}{,\_cs{_#1V},}}\_act
+ \_iftrue #3\_fi
+}
+\_def\_prepcommalist#1,{\_ifx\_end#1\_empty\_else #1,\_ea\_prepcommalist\_fi}
+
+ \_doc -----------------------------
+ The \`\moddef` `\<modifier> {<data>}` simply speaking does
+ `\def\<modifier>{<data>}`, but we need to respect
+ the family context. In fact, `\protected\def\_f:<current family>:<modifier>{<data>}` is
+ performed and the `\<modifier>` is defined as
+ \`\_famdepend``\<modifier>{_f:\_currfamily:<modifier>}`. It expands to
+ `\_f:\_currfamily:<modifier>` value if it is defined or it prints
+ the warning. When the `\_currfamily` value is
+ changed then we can declare the same `\<modifier>` with a different meaning.
+
+ When a user declares a prefixed variant of the `\<modifier>` then unprefixed
+ modifier name is used in internal macros, this is the reason why we are using
+ the \`\_remifirstunderscore``\_tmp` (where `\_tmp` expands to
+ `_<something>` or to `<something>`. The `\_remifirstunderscore`
+ redefines `\_tmp` in the way that it
+ expands only to `<something>` without the first `_`.
+
+ \`\_setnewmeaning` `<cs-name>=\_tmpa <by-what>` does exactly `\_let <csname>=\_tmpa`
+ but warning is printed if <cs-name> is defined already and it is not a variant
+ selector or font modifier.
+
+ \`\_addtomodlist` `<font modifier>` adds given modifier to \`\_modlist`
+ macro. This list is used after `\resetmod` when a new family is selected by
+ a family selector, see \`\_resetfam` macro.
+ This allows reinitializing the same current modifiers in the font context
+ after the family is changed.
+ \_cod -----------------------------
+
+\_def \_moddef #1#2{\_edef\_tmp{\_csstring#1}%
+ \_sdef{_f:\_currfamily:\_tmp}{\_addtomodlist#1#2\_reloading}%
+ \_protected \_edef \_tmpa{\_noexpand\_famdepend\_noexpand#1{_f:\_noexpand\_currfamily:\_tmp}}%
+ \_setnewmeaning #1=\_tmpa \moddef
+}
+\_protected \_def\_resetmod {\_cs{_f:\_currfamily:resetmod}} % private variant of \resetmod
+\_def \_resetfam{\_def\_addtomodlist##1{}\_resetmod
+ \_edef \_modlist{\_ea}\_modlist
+ \_let\_addtomodlist=\_addtomodlistb
+}
+\_def \_currfamily{} % default current family is empty
+\_def \_modlist{} % list of currently used modifiers
+
+\_def \_addtomodlist#1{\_addto\_modlist#1}
+\_let \_addtomodlistb=\_addtomodlist
+
+\_def\_famdepend#1#2{\_ifcsname#2\_endcsname \_csname#2\_ea\_endcsname \_else
+ \_ifx\_addtomodlist\_addtomodlistb
+ \_opwarning{\_string#1 is undeclared in family "\_currfamily", ignored}\_fi\_fi
+}
+\_def\_setnewmeaning #1=\_tmpa#2{%
+ \_ifx #1\_undefined \_else \_ifx #1\_tmpa \_else
+ \_opwarning{\_string#1 is redefined by \_string#2}%
+ \_fi\_fi
+ \_let#1=\_tmpa
+}
+\_public \moddef ;
+
+ \_doc -----------------------------
+ The \`\famvardef` `\<XX> {<data>}`
+ uses analogical trick like \^`\moddef` with
+ the \^`\_famdepend` macro. The auxiliary
+ \`\_famvardefA` `\<XX> \_ten<XX> \_tryload<XX> {<data>}` is used.
+ It does:
+ \begitems
+ * `\def \_tryload:<currfam>:<XX> {`\^`\fontdef`` \_ten<XX> {<data>}}` loads font `\_ten<XX>`,
+ * `\protected\def \<XX> {\_famdepend \<XX> {_f:<currfam>:<XX>}}`,
+ * `\def \_f:<currfam>:<XX> {\_tryload:<currfam>:<XX>\_ten<XX>}` keeps family dependent definition,
+ * `\def \_currvar:_ten<XX> {\<XX>}` in order to the \^`\currvar` macro work correctly.
+ \enditems
+ `\famvardef\tt` behaves somewhat differently: it doesn't re-define the
+ `\tt` macro which is defined as `\_tryloadtt \_tentt` in sections~\ref[math-preload]
+ and~\ref[unimath-codes]. It only re-defines the internal `\_tryloadtt` macro.
+ \_cod -----------------------------
+
+\_def\_famvardef#1{\_edef\_tmp{\_csstring#1}%
+ \_ea\_famvardefA \_ea#1\_csname _ten\_tmp\_ea\_endcsname
+ \_csname _tryload:\_currfamily:\_tmp\_endcsname
+}
+\_def\_famvardefA #1#2#3#4{% #1=\XX #2=\_tenXX #3=\_tryload:currfam:XX #4=data
+ \_isinlist{.\_rm\_bf\_it\_bi\currvar\_currvar}#1\_iftrue
+ \_opwarning{\_string\famvardef:
+ You cannot re-declare standard variant selector \_string#1}%
+ \_else
+ \_def#3{\_fontdef#2{#4}}%
+ \_protected\_edef\_tmpa{\_noexpand\_famdepend\_noexpand#1{_f:\_noexpand\_currfamily:\_tmp}}%
+ \_ifx #1\_tt \_let\_tryloadtt=#3\_else \_setnewmeaning #1=\_tmpa \famvardef \_fi
+ \_sdef{_f:\_currfamily:\_tmp}{#3#2}%
+ \_sdef{_currvar:\_csstring#2}{#1}%
+ \_fi
+}
+\_public \famvardef ;
+
+ \_doc -----------------------------
+ The \`\fontfam` `[<Font Family>]` does:
+ \begitems
+ * Convert its parameter to lower case and without spaces, e.g.\ `<fontfamily>`.
+ * If the file `f-<fontfamily>.opm` exists read it and finish.
+ * Try to load user defined `fams-local.opm`.
+ * If the `<fontfamily>` is declared in `fams-local.opm` or `fams-ini.opm`
+ read relevant file and finish.
+ * Print the list of declared families.
+ \enditems
+ The `fams-local.opm` is read by the \`\_tryloadfamslocal` macro. It sets
+ itself to `\_relax` because we need not load this file twice.
+ The \`\_listfamnames` macro prints registered font families to the
+ terminal and to the log file.
+ \_cod -----------------------------
+
+\_def\_fontfam[#1]{%
+ \_lowercase{\_edef\_famname{\_ea\_removespaces #1 {} }}%
+ \_isfile {f-\_famname.opm}\_iftrue \_opinput {f-\_famname.opm}%
+ \_else
+ \_tryloadfamslocal
+ \_edef\_famfile{\_trycs{_famf:\_famname}{}}%
+ \_ifx\_famfile\_empty \_listfamnames
+ \_else \_opinput {\_famfile.opm}%
+ \_fi\_fi
+}
+\_def\_tryloadfamslocal{%
+ \_isfile {fams-local.opm}\_iftrue
+ \_opinput {fams-local.opm}\_famfrom={}%
+ \_fi
+ \_let \_tryloadfamslocal=\_relax % need not to load fams-local.opm twice
+}
+\_def\_listfamnames {%
+ \_wterm{===== List of font families ======}
+ \_begingroup
+ \_let\_famtext=\_wterm
+ \_def\_faminfo [##1]##2##3##4{%
+ \_wterm{ \_space\_noexpand\fontfam [##1] -- ##2}%
+ \_let\_famalias=\_famaliasA}%
+ \_opinput {fams-ini.opm}%
+ \_isfile {fams-local.opm}\_iftrue \_opinput {fams-local.opm}\_fi
+ \_message{^^J}%
+ \_endgroup
+}
+\_def\_famaliasA{\_message{ \_space\_space\_space\_space -- alias:}
+ \_def\_famalias[##1]{\_message{[##1]}}\_famalias
+}
+\_public \fontfam ;
+
+ \_doc -----------------------------
+ When the `fams-ini.opm` or `fams-local.opm` files are read then we need
+ to save only a mapping from family names or alias names to the font family file
+ names. All other information is ignored in this case. But if these files
+ are read by the `\_listfamnames` macro or when printing a catalog then more
+ information is used and printed.\nl
+ \`\_famtext` does nothing or prints the text on the terminal.
+ \nl
+ \`\_faminfo` `[<Family Name>] {<comments>} {<file-name>} {<mod-plus-vars>}`
+ does\nl `\_def \_famf:<familyname> {<file-name>}` or prints information on
+ the terminal.
+ \nl
+ \`\_famalias` `[<Family Alias>]` does `\def \_famf:<familyalias> {<file-name>}`
+ where `<file-name>` is stored from the previous `\_faminfo` command. Or
+ prints information on the terminal.
+ \nl
+ \`\_famfrom` declares type foundry or owner or designer of the font family.
+ It can be used in `fams-ini.opm` or `fams-local.opm` and it is printed
+ in the font catalog.
+ \_cod -----------------------------
+
+\_def\_famtext #1{}
+\_def\_faminfo [#1]#2#3#4{%
+ \_lowercase{\_edef\_tmp{\_ea\_removespaces #1 {} }}%
+ \_sdef{_famf:\_tmp}{#3}%
+ \_def\_famfile{#3}%
+}
+\_def\_famalias [#1]{%
+ \_lowercase{\_edef\_tmpa{\_ea\_removespaces #1 {} }}%
+ \_sdef{_famf:\_tmpa\_ea}\_ea{\_famfile}%
+}
+\_newtoks\_famfrom
+\_input fams-ini.opm
+\_let\_famfile=\_undefined
+\_famfrom={}
+
+ \_doc -----------------------------
+ When the \^`\fontfam``[catalog]` is used then the file
+ `fonts-catalog.opm` is read. The macro \^`\_faminfo` is redefined here
+ in order to print catalog samples of all declared modifiers/variant
+ pairs. The user can declare different samples and different behavior of
+ the catalog, see the end of catalog listing for more information.
+ The default parameters
+ \`\catalogsample`, \`\catalogmathsample`, \`\catalogonly` and
+ \`\catalogexclude` of the catalog are declared here.
+ \_cod -----------------------------
+
+\_newtoks \_catalogsample
+\_newtoks \_catalogmathsample
+\_newtoks \_catalogonly
+\_newtoks \_catalogexclude
+\_catalogsample={ABCDabcd Qsty fi fl áéíóúüů řžč ÁÉÍÓÚ ŘŽČ 0123456789}
+
+\_public \catalogonly \catalogexclude \catalogsample \catalogmathsample ;
+
+ \_doc -----------------------------
+ The font features are managed in the \`\_fontfeatures` macro.
+ They have their implicit values saved in the \`\_defaultfontfeatures`
+ and the \`\setff` `{<features>}`
+ can add next font features. If there is the same font feature as the newly
+ added one then the old value is removed from the `\_fontfeatures` list.
+ \_cod -----------------------------
+
+\_def \_defaultfontfeatures {+tlig;}
+\_def \_setff #1{%
+ \_ifx^#1^\_let \_fontfeatures=\_defaultfontfeatures
+ \_else \_edef\_fontfeatures{\_fontfeatures #1;}\_fi
+ \_reloading
+}
+\_setff {} % default font features: +tlig;
+\_def\_removefeature #1{%
+ \_isinlist\_fontfeatures{#1}\_iftrue
+ \_def\_tmp ##1#1##2;##3\_relax{\_def\_fontfeatures{##1##3}}%
+ \_ea \_tmp \_fontfeatures \_relax
+ \_fi
+}
+\_public \setff ;
+
+ \_doc -----------------------------
+ The \`\setfontcolor` and \`\setletterspace` are macros based on the
+ special font features provided by \LuaTeX/ (and by \XeTeX/ too but it is not
+ our business). The \`\setwordspace` recalulates the `\fontdimen2,3,4`
+ of the font using the \`\setwsp` macro which is used by the
+ \^`\_doresizeunifont` macro. It activates a dummy font feature `+Ws` too in
+ order the font is reloded by the `\font` primitive (with independent
+ `\fontdimen` registers).
+ \_cod -----------------------------
+
+\_def\_savedfontcolor{}
+\_def\_savedletterspace{}
+\_def\_savedwsp{}
+
+\_def \_setfontcolor #1{\_removefeature{color=}%
+ \_edef\_tmp{\_calculatefontcolor{#1}}%
+ \_ifx\_tmp\_empty \_else \_edef\_fontfeatures{\_fontfeatures color=\_tmp;}\_fi
+ \_reloading
+}
+\_def \_setletterspace #1{\_removefeature{letterspace=}%
+ \_if^#1^\_else \_edef\_fontfeatures{\_fontfeatures letterspace=#1;}\_fi
+ \_reloading
+}
+\_def \_setwordspace #1{%
+ \_if^#1^\_def\_setwsp##1{}\_removefeature{+Ws}%
+ \_else \_def\_setwsp{\_setwspA{#1}}\_setff{+Ws}\_fi
+ \_reloading
+}
+\_def\_setwsp #1{}
+\_def\_setwspA #1#2{\_fontdimen2#2=#1\_fontdimen2#2%
+ \_fontdimen3#2=#1\_fontdimen3#2\_fontdimen4#2=#1\_fontdimen4#2}
+
+\_def\_calculatefontcolor#1{\_trycs{_fc:#1}{#1}} % you can define more smart macro ...
+\_sdef{_fc:red}{FF0000FF} \_sdef{_fc:green}{00FF00FF} \_sdef{_fc:blue}{0000FFFF}
+\_sdef{_fc:yellow}{FFFF00FF} \_sdef{_fc:cyan}{00FFFFFF} \_sdef{_fc:magenta}{FF00FFFF}
+\_sdef{_fc:white}{FFFFFFFF} \_sdef{_fc:grey}{00000080} \_sdef{_fc:lgrey}{00000025}
+\_sdef{_fc:black}{} % ... you can declare more colors...
+
+\_public \setfontcolor \setletterspace \setwordspace ;
+
+\_endcode %---------------------------------------------------
+
+
+\sec[fontsystem] The Font Selection System
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+The basic principles of the Font Selection System used in \OpTeX/
+was documented in the section~\ref[fontfam].
+
+\secc Terminology
+
+We distinguish between
+\begitems
+* {\em font switchers}, they are declared by the `\font` primitive or by
+ \^`\fontlet` or \~`\fontdef` macros, they select given font.
+* {\em variant selectors}, there are four basic variant selectors
+ \^`\rm`, \^`\bf`, \^`\it`, \^`\bi`, there is a special selector \^`\currvar`.
+ More variant selectors can be declared by the \~`\famvardef` macro.
+ They select the font depending on the given variant and on the {\em font context}
+ (i.e.\ on current family and on more features given by font modifiers).
+ In addition, \OpTeX/ defines \~`\tt` as variant selector
+ independent of chosen font family. It selects typewriter-like font.
+* {\em font modifiers} are declared in a family (`\cond`, `\caps`) or are
+ \"build in" (\^`\setfontsize``{<size spec>}`, \~`\setff{<features>}`).
+ They do appropriate change in the {\em font context} but do not select
+ the font.
+* {\em family selectors} (for example `\Termes`, `\LMfonts`),
+ they are declared typically in the {\em font family files}.
+ They enable to switch between font families, they do appropriate
+ change in the {\em font context} but do not select
+ the font.
+\enditems
+
+These commands set their values locally. When the \TeX/ group is
+left then the selected font and the {\em font context} are returned back to the values
+used when the group was opened. They have the following features:
+
+The {\em font context} is a set of macro values that will affect the
+selection of real font when the variant selector is processed. It includes the
+value of {\em current family}, current font size, and
+more values stored by font modifiers.
+
+The {\em family context} is the current family value stored in the font
+context. The variant selectors declared by \~`\famvardef` and
+font modifiers declared by \~`\moddef` are dependent on the {\em family context}.
+They can have the same names but different behavior in different families.
+
+The fonts registered in \OpTeX/ have their macros in the {\em font family files},
+each family is declared in one font family file with the name `f-famname.opm`.
+All families are collected in `fams-ini.opm` and users can give more
+declarations in the file `fams-local.opm`.
+
+\secc Font families, selecting fonts
+
+The \^`\fontfam` `[<Font Family>]` opens the relevant font family file where
+the `<Font Family>` is declared. The family selector is defined here by rules
+described in the section~\ref[fontfamfiles]. Font modifiers and variant
+selectors may be declared here.
+The loaded family is set as current and `\rm` variant selector is processed.
+
+The available declared font modifiers and declared variant selectors are
+listed in the log file when the font family is load. Or you can print
+`\fontfam[catalog]` to show available font modifiers and variant selectors.
+
+The font modifiers can be independent, like `\cond` and `\light`. They can
+be arbitrarily combined (in arbitrary order) and if the font family disposes
+of all such sub-variants then the desired font is selected (after variant
+selector is used). On the other hand, there are font modifiers that negates
+the previous font modifier, for example: `\cond`, `\extend`. You can reset
+all modifiers to their initial value by the \^`\resetmod` command.
+
+You can open more font families by more \^`\fontfam` commands. Then the
+general method to selecting the individual font is:
+
+\begtt \catcode`\<=13
+<family selector> <font modifiers> <variant selector>
+\endtt
+For example:
+\begtt
+\fontfam [Heros] % Heros family is active here, default \rm variant.
+\fontfam [Termes] % Termes family is active here, default \rm variant.
+{\Heros \caps \cond \it The caps+condensed italics in Heros family is here.}
+The Termes roman is here.
+\endtt
+
+There is one special command \^`\currvar` which acts as a variant selector.
+It keeps the current variant and the font of such variant is
+reloaded with respect to the current font context by the previously given family
+selector and font modifiers.
+
+You can use the \^`\setfontsize` `{<sizespec>}` command in the same sense as
+other font modifiers. It saves information about font size to the font
+context. See section~\ref[setfontsize]. Example:
+
+\begtt
+\rm default size \setfontsize{at14pt}\rm here is 14pt size \it italic is
+in 14pt size too \bf bold too.
+\endtt
+
+A much more comfortable way to resize fonts is using OPmac-like commands
+\~`\typosize` and \~`\typoscale`.
+These commands prepare the right sizes for math
+fonts too and they re-calculate many internal parameters like `\baselineskip`.
+See section~\ref[opmac-fonts] for more information.
+
+
+\secc Math Fonts
+%---------------
+
+Most font families are connected with a preferred Unicode-math font. This
+Unicode-math is activated when the font family is loaded. If you don't prefer
+this and you are satisfied with 8bit math CM+AMS fonts preloaded in the
+\OpTeX/ format then you can use command \^`\noloadmath` before you load a first
+font family.
+
+If you want to use your specially selected Unicode-math font then use
+\^`\loadmath` `{[<font_file>]}` or \^`\loadmath` `{<font_name>}` before first
+`\fontfam` is used.
+
+
+\secc[fontcommands] Declaring font commands
+%----------------------------
+
+Font commands can be font switches, variant selectors, font modifiers,
+family selectors and defined font macros doing something with fonts.
+
+\begitems
+* Font switches can be decared by `\font` primitive (see
+ section~\ref[fontprimitive]) or by \^`\fontlet` command (see
+ section~\ref[fontlet]) or by \~`\fontdef` command (see
+ sections~\ref[fontdef2] and~\ref[fontdef]).
+ When the font switches are used then they select the given font independently
+ of the current font context. They can be used
+ in `\output` routine (for example) because we need to set fixed fonts
+ in headers and footers.
+* Variant selectors are \^`\rm`, \^`\bf`, \^`\it`, \^`\bi`, \~`\tt` and \^`\currvar`. More
+ variant selectors can be declared by \~`\famvardef` command. They select a
+ font dependent on the current font context, see section~\ref[famvardef].
+ The `\tt` selector is documented in section~\ref[tt].
+* Font modifiers are \"build in" or declared by \~`\moddef` command.
+ They do modifications in the font context but don't select any font.
+ \begitems
+ * \"build-in" font modifiers are \^`\setfontsize` (see
+ section~\ref[setfontsize]), \~`\setff` (see section~\ref[setff]),
+ \~`\setfontcolor`, \~`\setletterspace` and \~`\setwordspace`
+ (see section~\ref[specff]). They are independent of font family.
+ * Font modifiers declared by \~`\moddef` depend on the font family and they
+ are typically declared in font family files, see
+ section~\ref[fontfamfiles].
+ \enditems
+* Family selectors set the given
+ font family as current and re-set data used by the family-dependent font
+ modifiers to initial values and to the currently used modifiers.
+ They are declared in font family files
+ by \~`\_famdecl` macro, see section~\ref[fontfamfiles].
+* Font macros can be defined arbitrarily by `\def` primitive by users.
+ See an example in section~\ref[fontmacros].
+\enditems
+
+All declaration commands mentioned here: `\font`, `\fontlet`, `\fontdef`, `\famvardef`,
+`\moddef`, `\_famdecl` and `\def` make local assignment.
+
+\secc[fontdef2] The `\fontdef` declarator in detail
+
+The general format for \^`\fontdef` usage is
+\begtt \catcode`\<=13
+\fontdef\<font switch> {\<family selector> <font modifiers> \<variant selector>}
+\endtt
+%
+where `\<family selector>` and `<font modifiers>` are optional and
+`\<variant selector>` is mandatory.
+
+The \^`\fontdef` does the following steps.
+It pushes the current font context to a stack, it does modifications of the font
+context by given `\<family selector>` and/or `<font modifiers>` and it
+finds the real font by `\<variant selector>`. This font is not selected but
+it is assigned to the declared `\<font switch>` (like `\font` primitive does
+it). Finally, `\fontdef` pops the font context stack, so the current
+font context is the same as it was before `\fontdef` is used.
+
+More about `\fontdef` command including examples is written in
+section~\ref[fontdef].
+
+
+\secc[famvardef] The `\famvardef` declarator
+
+You can declare a new variant selector by the \^`\famvardef` macro. This
+macro has similar syntax as \^`\fontdef`:
+\begtt \catcode`\<=13
+\famvardef\<new variant selector> {\<family selector> <font modifiers> \<variant selector>}
+\endtt
+%
+where `\<family selector>` and `<font modifiers>` are optional and
+`\<variant selector>` is mandatory.
+The `\<new variant selector>` should be used in the same sense as `\rm`,
+`\bf` etc. It can be used as the final command in next
+\^`\fontdef` or \^`\famvardef` declarators
+too. When the `\<new variant selector>` is used in the normal text then it does
+the following steps: pushes current font context to a stack, modifies font
+context by declared `\<family selector>` and/or `<font modifiers>`,
+runs following `\<variant selector>`.
+This last one selects a real font. Then pops the font context stack.
+The new font is selected but the font context has its original values.
+This is main difference between `\famvardef\foo{...}` and `\def\foo{...}`.
+
+Moreover, the \^`\famvardef` creates the `\<new variant selector>` family dependent.
+When the selector is used in another family context than it is defined then a warning is
+printed on the terminal \"<var selector> is undeclared in the current family"
+and nothing happens. But you can declare the same variant selector by
+\^`\famvardef` macro in the context of a new family. Then the same command
+may do different work depending on the current font family.
+
+Suppose that the selected font family provides the font modifier `\medium` for
+mediate weight of fonts. Then you can declare:
+\begtt
+\famvardef \mf {\medium\rm}
+\famvardef \mi {\medium\it}
+\endtt
+Now, you can use six independent variant selectors `\rm`, `\bf`, `\it`,
+`\bi`, `\mf` and `\mi` in the selected font family.
+
+A `\<family selector>` can be written before `<font modifiers>` in the
+`\famvardef` parameter. Then the `\<new variant selector>` is declared in
+the current family but it can use fonts from another family represented by
+the `\<family selector>`.
+
+When you are mixing fonts from more families then you probably run
+into a problem with incompatible ex-heights. This problem can be solved using
+\^`\setfontsize` and \^`\famvardef` macros:
+\begtt
+\fontfam[Heros] \fontfam[Termes]
+
+\def\exhcorr{\setfontsize{mag.88}}
+\famvardef\rmsans{\Heros\exhcorr\rm}
+\famvardef\itsans{\Heros\exhcorr\it}
+
+Compare ex-height of Termes \rmsans with Heros \rm and Termes.
+\endtt
+
+The variant selectors (declared by \~`\famvardef`) or font
+modifiers (declared by \~`\moddef`) are (typically) control sequences in user name
+space (`\mf`, `\caps`). They are most often declared in font family files and
+they are loaded by \^`\fontfam`. A conflict with such names in
+user namespace can be here. For example: if `\mf` is defined by a user and then
+`\fontfam[Roboto]` is used then `\famvardef\mf` is performed for Roboto
+family and the original meaning of `\mf` is lost. But \OpTeX/ prints warning
+about it. There are two cases:
+
+\begtt
+\def\mf{Metafont}
+\fontfam[Roboto] % warning: "The \mf is redefined by \famvardef" is printed
+ or
+\fontfam[Roboto]
+\def\mf{Metafont} % \mf variant selector redefined by user, we suppose that \mf
+ % is used only in the meaning of "Metafont" in the document.
+\endtt
+
+\secc[tt] The `\tt` variant selector
+
+\^`\tt` is an additional special variant selector which is defined as \"select typewriter
+font independently of the current font family". By default, the typewriter font-face
+from LatinModern font family is used.
+
+The \^`\tt` variant selector is used in \OpTeX/ internal macros
+\^`\_ttfont` (verbatim texts) and \^`\_urlfont` (printing URL's).
+
+You can redefine the behavior of `\tt` by \^`\famvardef`. For example:
+
+\begtt
+\fontfam[Cursor]
+\fontfam[Heros]
+\fontfam[Termes]
+\famvardef\tt{\Cursor\setff{-liga;-tlig}\rm}
+
+Test in Termes: {\tt text}. {\Heros\rm Test in Heros: {\tt text}}.
+Test in URL \url{http://something.org}.
+\endtt
+%
+You can see that `\tt` stay family independent. This is a special feature only
+for `\tt` selector. New definition is used in \^`\_ttfont` and \^`\_urlfont` too.
+It is recommended to use `\setff{-liga;-tlig}` to suppress the
+ligatures in typewriter fonts.
+
+If Unicode math font is loaded then the `\tt` macro selects typewriter
+font-face in math mode too. This face
+is selected from used Unicode math font and it is independent of
+`\famvardef\tt` declaration.
+
+
+\secc[fontmacros] Font commands defined by `\def`
+
+Such font commands can be used as fonts selectors for titles, footnotes,
+citations, etc. Users can define them.
+
+The following example shows how to define a \"title-font selector".
+Titles are not only bigger but they are typically in the bold variant. When a user puts
+`{\it...}` into the title text then he/she expects bold italic here, no normal
+italic. You can remember the great song by John Lennon \"Let It Be" and
+define:
+
+\begtt
+\def\titlefont{\setfontsize{at14pt}\bf \let\it\bi}
+...
+{\titlefont Title in bold 14pt font and {\it bold 14pt italics} too}
+\endtt
+
+\OpTeX/ defines similar internal commands \^`\_titfont`, \^`\_chapfont`, \^`\_secfont` and
+\^`\_seccfont`, see section~\ref[sections]. The commands \^`\typosize` and
+\^`\boldify` are used in these macros. They set the math fonts to given size too and they
+are defined in section~\ref[opmac-fonts].
+
+
+\secc[setff] Modifying font features
+%----------------------------
+
+Each OTF font provides \"font features". You can list these font features
+by `otfinfo -f font.otf`. For example, LinLibertine fonts provide `frac` font
+feature. If it is active then fractions like 1/2 are printed in a special
+form.
+
+The font features are part of the font context data.
+The macro \^`\setff` `{<feature>}` acts like family independent font modifier and
+prepares a new <feature>. You must use a variant selector in order to
+reinitialize the font with the new font feature. For example
+\^`\setff``{+frac}\rm` or \^`\setff``{+frac}`\^`\currvar`. You can declare a new variant
+selector too:
+
+\begtt
+\fontfam[LinLibertine]
+\famvardef \fraclig {\setff{+frac}\currvar}
+Compare 1/2 or 1/10 \fraclig to 1/2 or 1/10.
+\endtt
+
+If the used font does not support the given font feature then the font is reloaded
+without warning nor error, silently. The font feature is not activated.
+
+The `onum` font feature (old-style digits) is connected to `\caps` macro for
+Caps+SmallCaps variant in \OpTeX/ font family files. So you need not
+create a new modifier, just use `{\caps`\^`\currvar`` 012345}`.
+
+
+\secc[specff] Special font modifiers
+%---------------------------
+
+Despite the font modifiers declared in the font family file (and dependent on
+the font family), we have following font modifiers (independent of font
+family):
+
+\begtt \catcode`\<=13
+\setfontsize{<sizespec>} % sets the font size
+\setff{<font feature>} % adds the font feature
+\setfontcolor{<color>} % sets font color
+\setletterspace{<number>} % sets letter spacing
+\setwordspace{<scaling>} % modifies word spacing
+\endtt
+
+The \^`\setfontsize` command is described in the section \ref[setfontsize].
+The \^`\setff` command was described in previous subsection.
+
+\^`\setfontcolor` `{<color>}` specifies the color and the opacity of the text.
+The <color> parameter should be in the hexadecimal format of four bytes
+`<red><green><blue><opacity>`, for example `FF0080FF` means full red, zero
+green, half blue and full opacity. You can use names `red`, `green`, `blue`,
+`yellow`, `cyan`, `magenta`, `white`, `grey`, `lgrey` (without the backslash)
+instead of the hexadecimal specification.
+The empty parameter `<color>` means default black color.
+
+These colors of fonts are implemented using \LuaTeX/ internal font feature. This
+is different approach than using colors in section \ref[colors].
+
+\^`\setletterspace` `{<number>}` specifies the letter spacing of the font. The
+`<number>` is a decimal number without unit. The unit is supposed as 1/100 of
+the font size. I.e. `2.5` means 0.25 pt when the font is at 10 pt size. The
+empty parameter `<number>` means no letter spacing which is the default.
+
+\^`\setwordspace` `{<scaling>}` scales the default interword space (defined in the
+font) and its stretching and shrinking parameters by given `<scaling>`
+factor. For example `\setwordspace{2.5}` multiplies interword space by 2.5.
+
+If you need another font transformations, you can use `\setff`
+with following font features provided by Lua\TeX/:
+
+\begtt
+\setff{embolden=1.5}\rm % font is bolder because outline has nonzero width
+\setff{slant=0.2}\rm % font is slanted by a linear transformation
+\setff{extend=1.2}\rm % font is extended by a linear transformation.
+\setff{colr=yes}\rm % if the font includes colored characters, use colors
+\setff{upper}\rm % to uppercase (lower=lowecase) conversion at font level
+\endtt
+
+Use font transformations mentioned above and \^`\setletterspace`,
+\^`\setwordspace` with care. The best setting of these values is the default
+setting in every font, of course. If you really need to set a different
+letter spacing then it is strongly recommended to add `\setff{-liga}`
+to disable ligatures. And setting a positive letter spacing probably
+needs to scale interword spacing too.
+
+All mentioned font modifiers (except for `\setfontsize`) work only
+with Unicode fonts loaded by \^`\fontfam`.
+
+\secc[fontfamfiles] How to create the font family file
+%------------------------------------------------------
+
+\printdoctail f-heros.opm
+
+\printdoctail f-lmfonts.opm
+
+\secc How to register the font family in the Font Selection System
+%---------------------------------------------------------------
+
+\printdoctail fams-ini.opm
+
+\secc[exfont] Notices about extension of `\font` primitive
+%---------------------------------------------------------
+
+Unicode fonts are loaded by extended `\font` primitive. This extension is
+not activated in \OpTeX/ by default, \^`\initunifonts` macro activates it.
+You need not use \^`\initunifonts` explicitly if \^`\fontfam` macro is
+used because \^`\fontfam` runs it internally.
+
+The \^`\initunifonts` loads the Lua code from the Luaotfload package which
+implements the `\font` primitive extension. See its
+documentation `luaotfload-latex.pdf` for information about
+all possibilities of extended `\font` primitive.
+
+The \OpTeX/ format is initialized by `luatex` engine by default but
+you can initialize it by `luahbtex` engine too. Then the harfbuzz library is
+ready to use for font rendering as an alternative to build-in font renderer
+from Luaotfload. The harfbuzz library gives more features for rendering
+Indic and Arabic scripts. But it is not used as default, you need to specify
+`mode=harf` in the fontfeatures field when `\font` is used. Moreover, when
+`mode=harf` is used, then you must specify `script` too. For example
+
+\begtt
+\font\devafont=[NotoSansDevanagari-Regular]:mode=harf;script=dev2
+\endtt
+%
+If the `luahbtex` engine is not used then `mode=harf` is ignored. See
+Luaotfload documentation for more information.
+
+\endinput
+
+2021-02-25 \_ttunifont introduced
+2021-01-27 lua hack (print function) removed because luaotfload 3.17 removes bug.
+2020-12-12 \_modlist added, doc improved
+2020-04-18 \_tryloadfamslocal introduced
+ \_fontdecl -> \_famdecl with different concept
+2020-03-18 released