Method set_subset_fontname

src/__init__.py:7521–7543

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+'
            import random
            import string
            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)

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