Fwd: "International Domain Names" support in KDE

[Simon Josefsson]

Marc.Mutz at uni-bielefeld.de (Marc Mutz) writes:

> If you are talking about GNU's libidn, I'd advise against that. It would 
> duplicate _a lot_ of unicode tables that are already in Qt.

(Disclaimer: I have an interest in libidn)

Using Unicode tables from QT would likely violate the IDN
specifications, either directly or down the road, e.g.:

,---| IDNA, Security considerations
| Implementations MUST NOT use more recent normalization tables than the
| one referenced from this document, even though more recent tables may be
| provided by operating systems.  If an application is unsure of which
| version of the normalization tables are in the operating system, the
| application needs to include the normalization tables itself.  Using
| normalization tables other than the one referenced from this
| specification could have security and operational implications.
`----

,---- Stringprep
| This document is for Unicode version 3.2, and should not be considered
| to automatically apply to later Unicode versions.  The IETF, through
| an explicit standards action, may update this document as appropriate
| to handle later Unicode versions.
`----

Using a specific library for IDN, instead of QT, guarantees that the
proper Unicode tables for IDN purposes are used.  According to
<http://doc.trolltech.com/3.1/unicode.html> it seems QT references
Unicode 3.0.1.  Although the specifications only says "later versions
than 3.2", using earlier versions would cause similar problems.

If QT provided versioned Unicode tables (i.e., where you can be sure
you use Unicode 3.2, without any erratas not used by IDN) the QT
tables could be used.  But this would cause similar bloat as using
libidn, since QT will likely support Unicode 4.0 sooner or later...