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List:       xfree-fonts
Subject:    Re: [Fonts] Complex text layout and mapping screen coordinates
From:       Arun Sharma <arun () sharma-home ! net>
Date:       2002-02-25 8:15:43
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Keith Packard wrote:
> [...]
> > It seems to me that, by the current definition of the X protocol, the
> > client has to do complex text rendering, meaning that full support for
> > OpenType HAS to reside on the client side, and not on the server side.
> 
> That's correct.  

Can you be more specific ? Are you saying that it's a bad idea or that
it's illegal ? Do you think interpreting the argument to XDrawString()
as a sequence of character codes instead of a glyph string would be a
violation of the X protocol ?

I can see some advantages to implementing it on the server side, instead
of the client:

1. In a networked environment, people have control over their desktop
   machines, but not necessarily a large number of clients machines they're
   logging in to.

   In the context of supporting Indian languages (> 25 scripts), a large
   number of Indian language shaping engines will have to be installed
   on all these clients - which is unlikely if for eg, say the client is
   in a different country.

2. Client side fonts require the fonts to be installed on each one of
   the client machines - basically requiring that all the clients be
   localized. A server side solution only requires that the clients be
   internationalized - not necessarily localized.

3. If we ever were to make open type fonts network transparent,
   communicating font information to the client over the network may
   be expensive. It's the classic question of - do you move
   code to where data is or do you move data to where code is ?


> The solution is not to have the X server do layout -- it's not possible
> on that side of the wire as, in general, it requires arbitrary amounts
> of the character data to do the layout.

True. What's wrong with the client doing the layout, but using the
"services" of the X server for handling the information in the open type
font file ? If the client handles line breaks, it could possibly
send a line of data to the server at a time to query its extents.

	-Arun
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