[poppler] poppler::ustring encoding issue

Sun Mar 18 12:18:22 UTC 2018

Dear Albert,

please let me confirm your thought.

>> Maybe the consideration of GlobalParams::textEncoding
>> would be discussed in future when cpp frontend introduces an API
>> to modify it to non-Unicode values.
> 
> Honestly i don't think that makes any sense, why would you want that?

do you mean that "for cpp frontend, no need to care the cases that
non-Unicode encoding is specified in GlobalParams::textEncoding" ?

if so, its reason would be "because text(), text_list(), etc return
the texts by ustring objects, thus, even if the clients can set
GlobalParams::textEncoding to preferred non-Unicode encoding, they
cannot retrieve the text in the preferred non-Unicode encoding.
therefore, no need to expose GlobalParams::setTextEncoding() via
cpp frontend" ?

if this is what you meant, I agree that no need to care the cases
that non-Unicode encoding in GlobalParams::textEncoding.

The reason why I tried to care such cases was: some utils (like
pdftotext) allow users to specify non-Unicode encoding, so I was
wondering whether something similar would be added to cpp frontend
in future. If there's no such, it's good news for me.

Sorry for lengthy confirmation!

Regards,
mpsuzuki

Albert Astals Cid wrote:
> El dijous, 15 de març de 2018, a les 14:20:52 CET, suzuki toshiya va escriure:
>> Dear Albert,
>>
>> Thank you, I'm glad to hear that one of the direction could be
>> acceptable. Maybe the consideration of GlobalParams::textEncoding
>> would be discussed in future when cpp frontend introduces an API
>> to modify it to non-Unicode values.
> 
> Honestly i don't think that makes any sense, why would you want that?
> 
> Cheers,
>   Albert
> 
>> Now I'm discussing with Jeroen about how to fix other metadata
>> (not related with text_list() API), please wait a while.
>>
>> Regards,
>> mpsuzuki
>>
>> Albert Astals Cid wrote:
>>> El dimecres, 14 de març de 2018, a les 18:17:47 CET, suzuki toshiya va
>>>
>>> escriure:
>>>> Dear Adam,
>>>>
>>>> The 2nd option, iconv + GlobalParams::textEncoding solution might be
>>>> something like:
>>>> https://github.com/mpsuzuki/poppler/commit/80f088c4a94b151ddb90e05147a8dc
>>>> 456 5e01d89 ?
>>> Seems a bit too much to me.
>>>
>>> I've personally had had no time to test the other solution you sent
>>> (replacing unicode_GooString_to_ustring with from_utf8), but if that one
>>> works, it seems much simpler and straighforward and I'd like to commit
>>> that.
>>>
>>> Cheers,
>>>
>>>   Albert
>>>> Regards,
>>>> mpsuzuki
>>>>
>>>> suzuki toshiya wrote:
>>>>> Oops, I'm quite sorry for my mistake which make people confused as
>>>>> if my bits are in github.com/freedesktop. The right places are:
>>>>>
>>>>> sample PDF file
>>>>> https://github.com/mpsuzuki/poppler/blob/cpp-textlist-encoding-issue/cpp
>>>>> /t
>>>>> ests/HereIsUSASCII.pdf
>>>>>
>>>>> a easiest (and oversimplified) fix for this issue
>>>>> https://github.com/mpsuzuki/poppler/commit/9f2ac5773553a1b83bc8b7bbfc0bc
>>>>> 72
>>>>> 728fc85f9
>>>>>
>>>>> Regards,
>>>>> mpsuzuki
>>>>>
>>>>> suzuki toshiya wrote:
>>>>>> Dear Jeroen, Adam,
>>>>>>
>>>>>> Sorry for long latency about this issue. I would try to draft
>>>>>> the solutions suggested by Adam.
>>>>>>
>>>>>> Yet I'm not sure what I'm seeing now is same trouble with you.
>>>>>> In my case, the testing PDF is:
>>>>>> https://rawgit.com/freedesktop/poppler/1fb325f4b0a92ca28c110d46dc7a9dba
>>>>>> 2a
>>>>>> d94367/cpp/tests/HereIsUSASCII.pdf (maybe I should provide a PDF
>>>>>> showing
>>>>>> surrogate characters to
>>>>>> clarify the difference of UTF-8 & UTF-16)
>>>>>> I see your testing code shows same outputs for ASCII, but
>>>>>> different outputs for Cyrill etc. So, the encodings by text()
>>>>>> and textlist() are different, although their types are same
>>>>>> (ustring). It should be fixed. However, US-ASCII characters
>>>>>> are not garbled. If it's different from the trouble you're
>>>>>> seeing, please let me know.
>>>>>>
>>>>>> Now the easiest solution, using ustring::from_utf8() is drafted.
>>>>>> https://github.com/freedesktop/poppler/commit/9f2ac5773553a1b83bc8b7bbf
>>>>>> c0
>>>>>> bc72728fc85f9 Please check if it works for you. I think it works well
>>>>>> in
>>>>>> my
>>>>>> environment.
>>>>>>
>>>>>> I would proceed to the next one, implementing something like
>>>>>> ustring::from_utf8() which reflects GlobalParams::textEncoding.
>>>>>>
>>>>>> Regards,
>>>>>> mpsuzuki
>>>>>>
>>>>>> Adam Reichold wrote:
>>>>>>> Hello Jeroen,
>>>>>>>
>>>>>>> Am 06.03.2018 um 12:59 schrieb Jeroen Ooms:
>>>>>>>> On Tue, Mar 6, 2018 at 10:31 AM, Adam Reichold
>>>>>>>>
>>>>>>>> <adam.reichold at t-online.de> wrote:
>>>>>>>>> Hello mpsuzuki,
>>>>>>>>>
>>>>>>>>> from a glance at the code, it seems page::text uses
>>>>>>>>> ustring::from_utf8
>>>>>>>>> to convert Poppler's GooString into ustring which seems correct if
>>>>>>>>> GlobalParams::textEncoding has its default value of "UTF-8" .
>>>>>>>> I don't understand this part. Why is textEncoding a global property?
>>>>>>>> Shouldn't this be a property of single pdf document? Is there some
>>>>>>>> way
>>>>>>>> I can read a document's encoding from the C++ api (without including
>>>>>>>> GlobalParams.h).
>>>>>>>>
>>>>>>>> The pdf spec states that different strings may have different
>>>>>>>> encodings. Perhaps it would be possible to expose an encoding field
>>>>>>>> in
>>>>>>>> the ustring class? If there would be a way to know the encoding of a
>>>>>>>> ustring, I can get the raw data and convert it to a suitable encoding
>>>>>>>> myself. This would be much better than making assumptions.
>>>>>>> This is not the encoding of the text in the PDF document, but the
>>>>>>> encoding of the GooString that are returned by the internal Poppler
>>>>>>> API.
>>>>>>> Also I think the ustring class is intended to always store UTF-16
>>>>>>> encoded data.
>>>>>>>
>>>>>>> Best regards, Adam.
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