Can't view the corresponding text from font file

[CodePythonFollow]

I extracted the fonts using the method below

fonts = page.get_fonts(full=True)

for font in fonts:
    res = file.extract_font(font[0])

I use the following method to obtain text information

blocks = page.get_text("dict", flags=11)["blocks"]
for b in blocks:  # iterate through the text blocks
    for l in b["lines"]:  # iterate through the text lines
        for s in l["spans"]:  # iterate through the text spans
            print("")
            font_properties = "Font: '%s' (%s), size %g, color #%06x" % (
                s["font"],  # font name
                flags_decomposer(s["flags"]),  # readable font flags
                s["size"],  # font size
                s["color"],  # font color
            )
            print("Text: '%s'" %  s["text"])  # simple print of text
            print(f"box: {s['bbox']}")  # simple print of text
            print(font_properties)

out:

I can't see the corresponding text in the extracted font. font type: cid

The text "重要提示" not in font file.

I wonder if something went wrong with me？

[JorjMcKie]

This is not bug, but a "Discussions" item. Let me transfer first.

[ousia]

Do you really think this is an announcement? I think Q&A would make more sense here (writing that after mischaracterizing myself my previous discussion as announcement) .

[JorjMcKie]

of course you are right!

[JorjMcKie]

Back-translation information from a visible "glyph" on a page to its unicode, that was used to generate that glyph, may or may not be provided by a font - this is voluntary.

1. This information may be missing completely: then no text extraction is possible at all and you will only see invalid unicode symbols U+FFFD, '�' (white question mark with a black diamond shaped background).
2. This information may be incomplete: only some characters have been forgotten and therefore appear as �.
3. This information may be given, but wrong on purpose: this can is used to prevent text extraction. By not letting � appear, a program may not realize an extraction problem (although it is extractiing garbage) and will not invoke OCR - as it would otherwise.

[CodePythonFollow]

I have encountered the ' �' character you said, the above situation is a normal display Chinese, but the font file can only see the numbers without getting the Chinese characters.
Are you talking about incomplete font files？

� like it:

[JorjMcKie]

Are you talking about incomplete font files？

Yes, exactly. Could be that the font in question only has /ToUnicode entries for numbers and maybe always returns the space character code for all other glyphs.

WRT to "incomplete" fonts: The /ToUnicode information is optional for a font. There is no law or rule prescribing that a font must provide this information at all. Please recall that PDF has originally been created to display information for human reception. Not as a data store - things like text extraction, image extraction, etc. came later and - as I wrote - are not necessarily reliable.

[CodePythonFollow]

Thank you very much.