Around 22 o'clock on Feb 20, Joseph Koshy wrote:

> Font technologies like OpenType allow for the font renderer to do
> sophisticated transformations on the glyphs being rendered, including
> glyph substitution, glyph repositioning (e.g:- kerning) and the like.
> 
> If this rendering were to be done by an X server, how would a client
> map a screen coordinate back to an underlying location in the text
> that it is handling?

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.

> 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.  Systems like Pango are doing just that, accessing the 
OpenType tables directly from the font file and rendering text using the 
Xft library.  Server side fonts are a bad idea, and sophisticated text 
layout of this nature is one of the more significant features that simply 
cannot be grafted onto server-side font support.

The new version of the Xft library provides client-side font support for
all X servers, making it possible for applications to take advantage of the
capabilities client-side fonts bring to every desktop. The Render extension
provides the infrastructure to do this with performance equivalent to
server-side fonts.

Keith Packard        XFree86 Core Team        Compaq Cambridge Research Lab


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