Re: desktop schemas review [was: Re: GSettings migration status]

["A. Walton" <awalton gnome org>]

On Mon, Jul 5, 2010 at 10:06 PM, Russell Shaw <rjshaw netspace net au> wrote:
> Alexander Larsson wrote:
>>
>> On Sat, 2010-07-03 at 13:25 -0400, Ryan Lortie wrote:
>>>
>>> On Sat, 2010-07-03 at 13:37 +0200, Christian Persch wrote:
>>>>
>>>> This is a common error. Filenames need to be stored as "ay" and *NOT*
>>>> "s" (since "s" is UTF-8). (I think this needs some enhancement in
>>>> glib-compile-schemas to be able to still put a string in <default>.)
>>>
>>> I'm not sure I buy into your hardline stance on this one.
>>>
>>> I think it's not unreasonable to require that all filenames specified in
>>> the settings be in a valid encoding (whatever that encoding is) on their
>>> own filesystem (where "in a valid encoding" means "converts correctly to
>>> and from unicode").  In that case, utf8 is appropriate here.
>>
>> This is not right at all. Anything that does that is broken for two
>> reasons:
>>
>> 1) Technically for unix all filenames are "valid" if they are byte
>> strings without the characters zero and '/'. If you enforce anything
>> else on your filenames there *will* be actual files on the system that
>> you can't store references too. I've fixed soo many bugs from people
>> thinking filenames are "utf8 strings", they are just not, they are byte
>> arrays. This sucks, but its reality and we have to handle it.
>>
>> 2) Storing a "converted" pathname (for instance from filename encoding
>> to utf8) is a bad idea, even if it succeeds. First of all, the encoding
>> is runtime dependent (env vars) so may change over time, secondly
>> roundtripping to unicode and back does not necessarily get you the same
>> exact bytes back, so you might not be able to actually open the file.
>>
>> I've spent lots of work getting this right in e.g. gvfs, where raw
>> filenames are G_FILE_ATTRIBUTE_TYPE_BYTE_STRING, but e.g.
>> standard::display-name is G_FILE_ATTRIBUTE_TYPE_STRING. Please don't
>> break this. Filenames are not unicode strings, they are byte array
>> identifiers.
>
> Given that users may store file names in arbitrary encodings,
> what is the best way to determine the encoding for display in
> a file viewer?

We have an API for (almost) that, g_filename_display_name(). And
round-tripping through GFile querying info for the display name
attribute (standard::display-name) will do the same thing, in case
that is more convenient for your piece of code (e.g. checking for file
existence).

-A. Walton

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