Function set_subset_fontname

src_classic/utils.py:5221–5242

Generate a name prefix to tag a font as subset. We use a random generator to select 6 upper case ASCII characters. The prefixed name must be put in the font xref as the "/BaseFont" value and in the FontDescriptor object as the '/FontName' value.

(new_xref)

        return None

    def set_subset_fontname(new_xref):
        """Generate a name prefix to tag a font as subset.

        We use a random generator to select 6 upper case ASCII characters.
        The prefixed name must be put in the font xref as the "/BaseFont" value
        and in the FontDescriptor object as the '/FontName' value.
        """
        # The following generates a prefix like 'ABCDEF+'
        prefix = "".join(random.choices(tuple(string.ascii_uppercase), k=6)) + "+"
        font_str = doc.xref_object(new_xref, compressed=True)
        font_str = font_str.replace("/BaseFont/", "/BaseFont/" + prefix)
        df = doc.xref_get_key(new_xref, "DescendantFonts")
        if df[0] == "array":
            df_xref = int(df[1][1:-1].replace("0 R", ""))
            fd = doc.xref_get_key(df_xref, "FontDescriptor")
            if fd[0] == "xref":
                fd_xref = int(fd[1].replace("0 R", ""))
                fd_str = doc.xref_object(fd_xref, compressed=True)
                fd_str = fd_str.replace("/FontName/", "/FontName/" + prefix)
                doc.update_object(fd_xref, fd_str)
        doc.update_object(new_xref, font_str)
        return None

    def build_subset(buffer, unc_set, gid_set):
        """Build font subset using fontTools.