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#!/usr/bin/env python3
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# SPDX-License-Identifier: GPL-2.0-only
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# Copyright (C) Akira Yokosawa, 2024
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#
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# Ported to Python by (c) Mauro Carvalho Chehab, 2025
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"""
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Detect problematic Noto CJK variable fonts
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==========================================
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For ``make pdfdocs``, reports of build errors of translations.pdf started
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arriving early 2024 [1]_ [2]_.  It turned out that Fedora and openSUSE
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tumbleweed have started deploying variable-font [3]_ format of "Noto CJK"
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fonts [4]_ [5]_.  For PDF, a LaTeX package named xeCJK is used for CJK
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(Chinese, Japanese, Korean) pages.  xeCJK requires XeLaTeX/XeTeX, which
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does not (and likely never will) understand variable fonts for historical
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reasons.
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The build error happens even when both of variable- and non-variable-format
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fonts are found on the build system.  To make matters worse, Fedora enlists
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variable "Noto CJK" fonts in the requirements of langpacks-ja, -ko, -zh_CN,
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-zh_TW, etc.  Hence developers who have interest in CJK pages are more
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likely to encounter the build errors.
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This script is invoked from the error path of "make pdfdocs" and emits
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suggestions if variable-font files of "Noto CJK" fonts are in the list of
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fonts accessible from XeTeX.
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.. [1] https://lore.kernel.org/r/[email protected]/
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.. [2] https://lore.kernel.org/r/[email protected]/
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.. [3] https://en.wikipedia.org/wiki/Variable_font
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.. [4] https://fedoraproject.org/wiki/Changes/Noto_CJK_Variable_Fonts
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.. [5] https://build.opensuse.org/request/show/1157217
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Workarounds for building translations.pdf
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-----------------------------------------
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* Denylist "variable font" Noto CJK fonts.
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  - Create $HOME/deny-vf/fontconfig/fonts.conf from template below, with
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    tweaks if necessary.  Remove leading "".
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  - Path of fontconfig/fonts.conf can be overridden by setting an env
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    variable FONTS_CONF_DENY_VF.
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    * Template::
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        <?xml version="1.0"?>
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        <!DOCTYPE fontconfig SYSTEM "urn:fontconfig:fonts.dtd">
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        <fontconfig>
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        <!--
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        Ignore variable-font glob (not to break xetex)
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        -->
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            <selectfont>
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                <rejectfont>
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                    <!--
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                        for Fedora
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                    -->
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                    <glob>/usr/share/fonts/google-noto-*-cjk-vf-fonts</glob>
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                    <!--
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                        for openSUSE tumbleweed
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                    -->
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                    <glob>/usr/share/fonts/truetype/Noto*CJK*-VF.otf</glob>
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                </rejectfont>
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            </selectfont>
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        </fontconfig>
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    The denylisting is activated for "make pdfdocs".
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* For skipping CJK pages in PDF
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  - Uninstall texlive-xecjk.
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    Denylisting is not needed in this case.
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* For printing CJK pages in PDF
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  - Need non-variable "Noto CJK" fonts.
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    * Fedora
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      - google-noto-sans-cjk-fonts
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      - google-noto-serif-cjk-fonts
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    * openSUSE tumbleweed
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      - Non-variable "Noto CJK" fonts are not available as distro packages
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        as of April, 2024.  Fetch a set of font files from upstream Noto
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        CJK Font released at:
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          https://github.com/notofonts/noto-cjk/tree/main/Sans#super-otc
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        and at:
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          https://github.com/notofonts/noto-cjk/tree/main/Serif#super-otc
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        then uncompress and deploy them.
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      - Remember to update fontconfig cache by running fc-cache.
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.. caution::
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    Uninstalling "variable font" packages can be dangerous.
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    They might be depended upon by other packages important for your work.
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    Denylisting should be less invasive, as it is effective only while
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    XeLaTeX runs in "make pdfdocs".
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"""
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import os
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import re
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import subprocess
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import textwrap
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import sys
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class LatexFontChecker:
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    """
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    Detect problems with CJK variable fonts that affect PDF builds for
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    translations.
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    """
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    def __init__(self, deny_vf=None):
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        if not deny_vf:
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            deny_vf = os.environ.get('FONTS_CONF_DENY_VF', "~/deny-vf")
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        self.environ = os.environ.copy()
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        self.environ['XDG_CONFIG_HOME'] = os.path.expanduser(deny_vf)
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        self.re_cjk = re.compile(r"([^:]+):\s*Noto\s+(Sans|Sans Mono|Serif) CJK")
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    def description(self):
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        """
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        Returns module description.
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        """
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        return __doc__
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    def get_noto_cjk_vf_fonts(self):
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        """
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        Get Noto CJK fonts.
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        """
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        cjk_fonts = set()
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        cmd = ["fc-list", ":", "file", "family", "variable"]
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        try:
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            result = subprocess.run(cmd,stdout=subprocess.PIPE,
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                                    stderr=subprocess.PIPE,
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                                    universal_newlines=True,
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                                    env=self.environ,
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                                    check=True)
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        except subprocess.CalledProcessError as exc:
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            sys.exit(f"Error running fc-list: {repr(exc)}")
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        for line in result.stdout.splitlines():
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            if 'variable=True' not in line:
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                continue
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            match = self.re_cjk.search(line)
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            if match:
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                cjk_fonts.add(match.group(1))
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        return sorted(cjk_fonts)
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    def check(self):
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        """
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        Check for problems with CJK fonts.
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        """
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        fonts = textwrap.indent("\n".join(self.get_noto_cjk_vf_fonts()), "    ")
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        if not fonts:
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            return None
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        rel_file = os.path.relpath(__file__, os.getcwd())
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        msg = "=" * 77 + "\n"
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        msg += 'XeTeX is confused by "variable font" files listed below:\n'
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        msg += fonts + "\n"
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        msg += textwrap.dedent(f"""
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                For CJK pages in PDF, they need to be hidden from XeTeX by denylisting.
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                Or, CJK pages can be skipped by uninstalling texlive-xecjk.
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                For more info on denylisting, other options, and variable font, run:
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                    tools/docs/check-variable-fonts.py -h
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            """)
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        msg += "=" * 77
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        return msg
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