Re: FW: Displaying Plane 1 characters

From: Mark Davis (mark_macchiato@yahoo.com)
Date: Mon Nov 09 1998 - 21:38:54 EST


Microsoft is absolutely correct in this matter. Unicode 2.1
conformance does not require surrogates to be supported.

Where UTF-8 is used, conformance does require surrogate pairs to be
properly handled, cf A-7.

Mark

---Lori Brownell <loribr@microsoft.com> wrote:
>
>
> > Surrogate pairs are not defined/supported in current versions of
Win32. In
> > other words, a surrogate pair is treated as two undefined 16-bit
Unicode
> > code values. However, MutliByteToWideChar and WideCharToMultiByte
> > conversions between UTF-8 and UCS-2 will preserve surrogate pairs
without
> > a loss of data. The Win32 conversions do not support UCS-4 32-bit
chars
> > (non-BMP).
> >
> Microsoft believes that non-BMP and surrogate pair support is not
required
> for Unicode 2.x conformance based on the Conformance Requirements
documented
> in Section 3.1 of The Unicode Standard 2.0. Clause C4 does not
require
> support of surrogates, rather it prohibits the use of unpaired
surrogates to
> represent other characters (just as C6 says you can't assign an
abstract
> character to an unassigned code value). Microsoft products do not
assign any
> control or representation of data to unpaired surrogates, it simply
treats
> them as unassigned Unicode code values.
>
> > -----Original Message-----
> > From: Markus Scherer [SMTP:schererm@us.ibm.com]
> > Sent: Monday, November 09, 1998 6:37 AM
> > To: Unicode List
> > Subject: Re: Displaying Plane 1 characters
> >
> > Sorry if this was answered before -
> >
> > Microsoft Windows Win32 APIs up to and including NT 5.0 beta 2
ignore or
> > even
> > mistreat surrogate pairs and other representations (UTF-8) of
non-BMP
> > characters.
> > Conversions between UTF-8 and UCS-2 yield incorrect results for
non-BMP
> > characters, at least if "correct" means UTF-16 as specified in
Unicode 2.0
> > .
> > Non-BMP characters are destroyed in these conversions.
> > I don't know if the OpenType technology supports this.
> >
> > markus
> >
> >
> > PS: Microsoft advertises compliance with Unicode 2.12 . I expect
them to
> > fulfill it eventually...
> >
> >
> > Markus Scherer IBM RTP +1 919 486 1135 Dept. Fax +1 919 254 6430
> > scherer@raleigh.ibm.com
>
>
>

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