[Openicc] Renaming an ICC profile

[Richard Hughes]

Hi all,

One frequent request from users seems to be the ability to "rename" an
ICC profile in the GUI. What they mean is to change the description
value of user-local profiles (rather than system-installed profiles).
Allowing this does pose a few problems:

* We don't want to restrict the user to ASCII for v2 profiles
* We don't really want to change the header checksum otherwise the
mapping to devices will be destroyed

I see two ways around this. For a v4 profile we can of course just use
a MLUC value and store in the UTF16 values of what the user entered,
but should the locale of this be the users locale (e.g. pt_BR) or the
system locale (e.g. C) -- if it's the former then we probably need to
store an "English" version of the profile description, although I'm
not sure how that could be generated. I'm not sure if applications
assume that they'll always be a non-NULL locale entry in the MLUC
(lcms2 seems to do the right thing) or if such a program would just be
considered buggy.

For a v2 profile, I suppose it makes sense to use the non-standard
cmsSigProfileDescriptionTagML and then use the MLUC value like above.
This means applications need to read the cmsSigProfileDescriptionTagML
and if present prefer this over the cmsSigProfileDescriptionTag value.
This seems to be what Apple does in OS-X, although I think in Linux
only programs using libcolord will do the fallback like this at the
moment. A safer bet might be to write cmsSigProfileDescriptionTagML
and then some ASCIIfied version of the description to
cmsSigProfileDescriptionTag although that seems to be inviting users
to report bugs about profiles they've renamed with accented chars that
are not showing in things like scribus and inkscape.

For the second point, we could introduce a new metadata property,
something like "OriginalChecksum" which would represent the original
file checksum and use that for matching profiles to devices. This
would be easily abstracted away in libcolord, so end applications
wouldn't even be aware the checksum had changed, just that the "title"
had been modified.

I've not written any code yet, but I'm open for suggestions and
feedback. Thanks.

Richard