[RFC PATCH 1/3] docs: pdfdocs: Refactor config for CJK document

[Akira Yokosawa <akiyks@gmail.com>]

To make generated LaTeX code portable across systems with different sets
of available fonts, convert font-availability check in python code to
LaTeX code by using a conditional command provided by the "fontspec"
package.

This will help those who want to run Sphinx on one machine/container
and run latexmk on other machines/containers with different font
configurations.

Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
---
 Documentation/conf.py | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/Documentation/conf.py b/Documentation/conf.py
index 7d92ec3e5b6e..22f083bafaae 100644
--- a/Documentation/conf.py
+++ b/Documentation/conf.py
@@ -358,26 +358,23 @@ latex_elements = {
 # At least one book (translations) may have Asian characters
 # with are only displayed if xeCJK is used
 
-cjk_cmd = check_output(['fc-list', '--format="%{family[0]}\n"']).decode('utf-8', 'ignore')
-if cjk_cmd.find("Noto Sans CJK SC") >= 0:
-    latex_elements['preamble']  += '''
+latex_elements['preamble']  += '''
+    \\IfFontExistsTF{Noto Sans CJK SC}{
 	% This is needed for translations
-        \\usepackage{xeCJK}
-        \\setCJKmainfont{Noto Sans CJK SC}
+	\\usepackage{xeCJK}
+	\\setCJKmainfont{Noto Sans CJK SC}
 	% Define custom macros to on/off CJK
 	\\newcommand{\\kerneldocCJKon}{\\makexeCJKactive}
 	\\newcommand{\\kerneldocCJKoff}{\\makexeCJKinactive}
-	% To customize \sphinxtableofcontents
+	% Inactivate CJK after tableofcontents (using etoolbox)
 	\\usepackage{etoolbox}
-	% Inactivate CJK after tableofcontents
 	\\apptocmd{\\sphinxtableofcontents}{\\kerneldocCJKoff}{}{}
-     '''
-else:
-    latex_elements['preamble']  += '''
+    }{ % No CJK font
 	% Custom macros to on/off CJK (Dummy)
 	\\newcommand{\\kerneldocCJKon}{}
 	\\newcommand{\\kerneldocCJKoff}{}
-     '''
+    }
+'''
 
 # Fix reference escape troubles with Sphinx 1.4.x
 if major == 1:
-- 
2.17.1