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

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

Hi,

I have just joined the list.

Let me first say thanks to Mr. Joseph Koshy for evaluating
the IndiX system. It's really good to have someone who can
independently evaluate our work. Thanks a lot Mr. Koshy!
Also I am thankful to Mr. Tapan Parikh for informing me
about this mailing list.

There are certain points which I want to put comments on.

--- Joseph Koshy wrote:
> [[ This is a 28MB download. I wonder why they didn't
> (also)
> put up a "diff" wrt. XFree86 sources instead. ]]

Agreed. I was too lazy to put 'diff' on the website :(.
I'll do it.

> 
> IMO, the plus points of this work are:

At this moment, I don't want to say anything about plus
point of IndiX. I rather like to discuss negative points so
that I can improve the design and the system :) 

> 
> The NCST changes are, unfortunately, intrusive, and break
> the semantics of the X Window system protocol.
> 
> The problem with the NCST design arises from confusion
> over
> character codes and the glyph indices used in X11 text
> drawing calls.
> 

I have some objection on this point. X11 text drawing calls
accepts character codes and send them to the X Server along
with other data in the form of a request. We have not
changed this semantic. This character codes are then used
by the subsequent font library to get the glyph codes.

> 
> In the NCST work however, all text strings fed into X11
> text calls are assumed to be UNICODE character streams
> encoded in UTF-8 format.

True. This assumption we have taken. There are certain
reasons behind this but we'll discuss them later on.

> The NCST system cannot be considered an implementation of
> the X Window System protocol.  Applications using the
> NCST
> X library will not work correctly on other X servers and
> applications compiled on other systems will not work
> correctly on the NCST X server.

Again this is not true. I have been downloading binary RPMS
and using it on my machine where IndiX has been installed.
You can also use applications compiled on the IndiX system
and use it without any problem on your machine.

> 
> Compatibility of clients using the NCST X11 library with
> `stock' X servers is broken because of a change to
> XQueryTextExtents(): in the NCST system, the text string
> sent over to the X server is assumed to be in UTF-8
> format
> and is first converted to UCS-2 by their X11 library. 
> Thus
> the bytes (in UCS-2 format) that get sent out will be
> quite different from what the client passed in.  The NCST
> X
> server will deal correctly with this UCS-2 encoded data,
> but stock X servers will not.

Err! Please carefully see the source code of 
xc/lib/X11/QuTextExt.c in original XFree86. It also first
converts the string into UCS-2 before sending request to
the X Server. The only difference between the conversion is
that, originally X Server pads an extra byte to each
element of the string to make it UCS-2. We assume incoming
sequence into UTF-8 and convert it into UCS-2. The changes
made in IndiX was earlier breaking relationship with other
foreign languages like French, German (all with iso-8859-*
encoding). But now I am taking care of this also.

> 
> Nice system, nice code; unfortunately not compatible with
> the X Window System protocol.

In my view, it is compatible with the X Window System
protocol.

Thanks,
Keyur


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