Re: Updating the XLFD specification

From: Markus Kuhn (
Date: Fri Apr 09 1999 - 14:48:10 EDT

Juliusz Chroboczek wrote on 1999-04-09 17:00 UTC:
> 2. We need a way to specify planes of a multi-plane encoding. The
> intent would be to specify a multi-plane encoding as a family of
> single-plane encodings, which avoids the need for an extension to the
> X11 protocl. How do you specify a font that is encoded according to
> Plane 1 of ISO 10646?

Roman Czyborra <> proposed a long time ago on
the mailing list (check the archives on something like

  *-iso10646-01 for plane 1
  *-iso10646-02 for plane 2

etc. The proposal sounds a bit like what you had in mind and was
commonly greeted in the following discussion as an ugly hack if I
remember correctly. There was not much progress on this topic since
then, because at the moment there is nothing really interesting for X11
users outside the BMP. The clean solution would have been to extend the
X protocol to allow the handling of 24-bit or even 32-bit fonts, but
this sounds like a more severe change to me. The problem with the format
is that the CHARSET_ENCODING field is now again used for two orthogonal
purposes: encoding offset (= plane selection) and subset indication.

I do not think it is an urgent problem at the moment, and it should
probably be discussed at a larger scale which approach is in the long
term the best to take. The option of making the X11 system 32-bit font
capable should be thoroughly investigated first before ugly hacks like
indicating the plane in the CHARSET_ENCODING field are proposed.


Markus G. Kuhn, Computer Laboratory, University of Cambridge, UK
Email: mkuhn at,  WWW: <>

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