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

[Alexander Larsson <alexl redhat com>]

On Wed, 2010-07-07 at 10:01 -0400, Shaun McCance wrote:
> On Mon, 2010-07-05 at 10:43 +0200, 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.
> 
> Perhaps we should add some convenience API to GSettings.
> 
> GFile *   g_settings_get_file   (GSettings   *settings,
>                                  const gchar *key);
> gboolean  g_settings_set_file   (GSettings   *settings,
>                                  const gchar *key,
>                                  GFile       *file);
> 
> If this API insisted on the type being "ay", it would
> encourage developers to do the right thing.

Well, the serialization form of a GFile is a uri, and uris are ascii
strings. So, in this case "ay" is not needed. However, that doesn't mean
an API like this is not useful.

-- 
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 Alexander Larsson                                            Red Hat, Inc 
       alexl redhat com            alexander larsson gmail com 
He's a deeply religious one-eyed cyborg who knows the secret of the alien 
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