docs: pdfdocs: Add CJK-language-specific font settings

zh_TW, ko_KR, and ja_JP translations have their preferred glyph sets
different from that of zh_CN.

To switch CJK font in the middle of the translations, introduce custom
LaTeX macros listed below:

    \kerneldocBeginSC
    \kerneldocEndSC
    \kerneldocBeginTC
    \kerneldocEndTC
    \kerneldocBeginKR
    \kerneldocEndKR
    \kerneldocBeginJP
    \kerneldocEndJP

, and embed a pair of macros in each language's index.rst.

NOTE 1: Update of zh_TW/index.rst is deferred to a follow-up change.

NOTE 2: Custom macros added here do not imply \kerneldocCJK(on|off).
This is intentional.  For example, \kerneldocCJKoff needs to be
at the top of Italian translations' index.rst for the footer of
final zh_TW page to be properly typeset.

Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Link: https://lore.kernel.org/r/31906baf-7490-68cd-7153-4e4d320fb9b0@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/conf.py

@@ -361,10 +361,51 @@ latex_elements['preamble']  += '''
 	% This is needed for translations
 	\\usepackage{xeCJK}
 	\\setCJKmainfont{Noto Sans CJK SC}
+	\\setCJKsansfont{Noto Sans CJK SC}
+	\\setCJKmonofont{Noto Sans Mono CJK SC}
+	% CJK Language-specific font choices
+	\\newCJKfontfamily[SCmain]\\scmain{Noto Sans CJK SC}
+	\\newCJKfontfamily[SCsans]\\scsans{Noto Sans CJK SC}
+	\\newCJKfontfamily[SCmono]\\scmono{Noto Sans Mono CJK SC}
+	\\newCJKfontfamily[TCmain]\\tcmain{Noto Sans CJK TC}
+	\\newCJKfontfamily[TCsans]\\tcsans{Noto Sans CJK TC}
+	\\newCJKfontfamily[TCmono]\\tcmono{Noto Sans Mono CJK TC}
+	\\newCJKfontfamily[KRmain]\\krmain{Noto Sans CJK KR}
+	\\newCJKfontfamily[KRsans]\\krsans{Noto Sans CJK KR}
+	\\newCJKfontfamily[KRmono]\\krmono{Noto Sans Mono CJK KR}
+	\\newCJKfontfamily[JPmain]\\jpmain{Noto Sans CJK JP}
+	\\newCJKfontfamily[JPsans]\\jpsans{Noto Sans CJK JP}
+	\\newCJKfontfamily[JPmono]\\jpmono{Noto Sans Mono CJK JP}
 	% Define custom macros to on/off CJK
 	\\newcommand{\\kerneldocCJKon}{\\makexeCJKactive}
 	\\newcommand{\\kerneldocCJKoff}{\\makexeCJKinactive}
-	% To customize \sphinxtableofcontents
+	\\newcommand{\\kerneldocBeginSC}{%
+	    \\begingroup%
+	    \\scmain%
+	}
+	\\newcommand{\\kerneldocEndSC}{\\endgroup}
+	\\newcommand{\\kerneldocBeginTC}{%
+	    \\begingroup%
+	    \\tcmain%
+	    \\renewcommand{\\CJKsfdefault}{TCsans}%
+	    \\renewcommand{\\CJKttdefault}{TCmono}%
+	}
+	\\newcommand{\\kerneldocEndTC}{\\endgroup}
+	\\newcommand{\\kerneldocBeginKR}{%
+	    \\begingroup%
+	    \\krmain%
+	    \\renewcommand{\\CJKsfdefault}{KRsans}%
+	    \\renewcommand{\\CJKttdefault}{KRmono}%
+	}
+	\\newcommand{\\kerneldocEndKR}{\\endgroup}
+	\\newcommand{\\kerneldocBeginJP}{%
+	    \\begingroup%
+	    \\jpmain%
+	    \\renewcommand{\\CJKsfdefault}{JPsans}%
+	    \\renewcommand{\\CJKttdefault}{JPmono}%
+	}
+	\\newcommand{\\kerneldocEndJP}{\\endgroup}
+	% To customize \\sphinxtableofcontents
 	\\usepackage{etoolbox}
 	% Inactivate CJK after tableofcontents
 	\\apptocmd{\\sphinxtableofcontents}{\\kerneldocCJKoff}{}{}
@@ -372,6 +413,14 @@ latex_elements['preamble']  += '''
 	% Custom macros to on/off CJK (Dummy)
 	\\newcommand{\\kerneldocCJKon}{}
 	\\newcommand{\\kerneldocCJKoff}{}
+	\\newcommand{\\kerneldocBeginSC}{}
+	\\newcommand{\\kerneldocEndSC}{}
+	\\newcommand{\\kerneldocBeginTC}{}
+	\\newcommand{\\kerneldocEndTC}{}
+	\\newcommand{\\kerneldocBeginKR}{}
+	\\newcommand{\\kerneldocEndKR}{}
+	\\newcommand{\\kerneldocBeginSC}{}
+	\\newcommand{\\kerneldocEndKR}{}
     }
 '''
 

Documentation/translations/ja_JP/index.rst

@@ -3,6 +3,7 @@
 	\renewcommand\thesection*
 	\renewcommand\thesubsection*
 	\kerneldocCJKon
+	\kerneldocBeginJP
 
 Japanese translations
 =====================
@@ -11,3 +12,7 @@ Japanese translations
    :maxdepth: 1
 
    howto
+
+.. raw:: latex
+
+	\kerneldocEndJP

Documentation/translations/ko_KR/index.rst

@@ -3,6 +3,7 @@
 	\renewcommand\thesection*
 	\renewcommand\thesubsection*
 	\kerneldocCJKon
+	\kerneldocBeginKR
 
 한국어 번역
 ===========
@@ -26,3 +27,4 @@
 .. raw:: latex
 
     \normalsize
+    \kerneldocEndKR

Documentation/translations/zh_CN/index.rst

@@ -5,6 +5,7 @@
 	\renewcommand\thesection*
 	\renewcommand\thesubsection*
 	\kerneldocCJKon
+	\kerneldocBeginSC
 
 .. _linux_doc_zh:
 
@@ -189,3 +190,7 @@ TODOList:
 ----------
 
 * :ref:`genindex`
+
+.. raw:: latex
+
+	\kerneldocEndSC