Re: emacs could not show this symbol.

[Peter Dyballa]

Am 26.02.2008 um 12:00 schrieb anhnmncb:

> I don't seem it's font's problem. I think that urxvt's font
> selection mechanism is great, if a font doesn't contain a symbol in  
> that
> encoding, it will find another font to display it, don't know whether
> emacs could implement this technique?

It would not be that easy.

A terminal emulation has an easy job: display things in one encoding.  
GNU Emacs supports some dozens. Less than a handful are sensible,  
IMO, i.e. Unicode based. Some encodings are 8 bit, left from the  
child days of some operating systems, other are 16 bit or more, most  
of them for some restricted national use.

Ideally GNU Emacs would need to construct font sets for all these  
encodings, at least for those in use. It also supports scripts  
(writing systems) and their languages (language environments). This  
*can* mean that for different font sizes and font variants (regular,  
bold, italic, bold italic) 100 MB of fonts would be loaded into  
memory, at least for 16 bit encodings. The size needed might be  
reduced when 8 bit encodings could be derived from 16 bit encodings  
(for example ISO 8859-11 and TIS620 are the same and both could map  
into Unicode).

The idea of font backends eases this situation by delegating font  
handling to the operating system (what Mac OS X or MS Losedos or ...  
or X11 are providing in some way, some better, some worse). To make  
this work the OS has to know what its fonts support/deliver. This  
information usually is derived from the fonts. Some provide enough  
information, others tend to hide it. The it becomes difficult.

With fc-list you can check what your system provides. The language  
name used is based on RFC 3066 which in turn references ISO 639. A  
font with your Thai character could be searched for with:

        fc-list :lang=th

Much more options are possible. To find all monospaced fonts with  
Thai support:

        fc-list : file lang spacing | grep spac | egrep 'lang=.*th'

This is because fc-list tends to report either too much or not enough  
– or I need more practise with fc-list!

--
Greetings

  Pete

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