Re: [Indic-computing-devel] NCST IndiX examined

[Keyur S. <key...@ya...>]

--- Joseph Koshy <jk...@Fr...> wrote:
> 
> 
> Dear Keyur,
> 
> ks> When Xlib converts 8-bit string into 16-bit string,
> it
> ks> first send MSB first. This is same as Little-Endian
> UCS-2. 
> 
> The X11 Protocol definition predates Unicode.  This isn't
> Little-Endian UCS-2, its just a 2-byte encoding of the 8
> bit glyph
> indices.

I don't say that "it is" UCS-2. I say that it is "same as"
UCS-2 (or compatible with UCS-2).

> 
> ks> How can client have knowledge about the glyph
> indices?
> 
> That is what the encoding field in the long name of X
> fonts is for.
> For Latin fonts this will be `-iso8859-1' meaning the
> font is encoded
> compatibly with the ISO8859-1 character encoding.

As you said, this is really character encoding not font
encoding. Some distinction should be made between
"character" and "glyph".

-----------
According to Unicode standard (see glossary), a character
is 
(1) The smallest component of written language that has
semantic value; refers to the abstract meaning and/or
shape, rather than a specific shape (see also glyph),
though in code tables some form of visual representation is
essential for the reader's understanding.
(2) Synonym for abstarct character
(3) Loosely, the basic unit of encoding for the Unicode
character encoding, a 16-bit unit of textual
representation.
(4) Synonym for code value.
(5) The English name for the ideographic written elements
of Chinese origin.

Abstract character : A unit of information used for the
organization, control, or representation of textual data.
(See also character (1, 2))

And glyph has been defined as
(1) An abstract form that represents one or more glyph
images.
(2) A synonym for glyph image. In displaying Unicode
character data, one or more glyphs may be selected to
depict a particular character. These glyphs are selected by
a rendering engine during composition and layout
processing.
---------------

As can be depicted from the above definations, a client
pass "something" that has semantic value, means
"characters". One or more glyphs may be selected to display
a particular character. So client is in no position to
decide upon the glyph indices to be used for a character.
It is totally at the sole discretion of font designer to
select _proper_ glyph(s) for a character. We can't say that
particular glyph should be used for a character.
 
> You can have fonts that are not indexed by character
> codes and fonts
> that follow different encoding schemes e.g:- hp-roman8. 

Can you give me few font formats used in X Window system
which doesn't use mapping table? Even in case of different
encoding like hp-roman8 or font coding like ISFOC, there
should be mapping from these encoding values to the glyph
codes. In case of ISFOC, font glyph encoding matches with
ISFOC encoding.

> The client
> has to select the correct glyph indices in the X text
> drawing calls,
> appropriately.

In 

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