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Re: Type1 fonts & status of various backends


From: Fred Kiefer
Subject: Re: Type1 fonts & status of various backends
Date: Mon, 16 Oct 2000 21:12:07 +0200

Hi Wim,

fine that you looked into the Postscript font suff. I will try to answer
some of your questions:

> 2.  What is the goal of the various backends?
>         As far as I know there are three (potential) backends for X11
>         systems.
> 
>         - xgps   based on XLib. Does support minimal display
>                 postscript in order to make the AppKit part work.
>                 Most stable and easiest to get working right now.
> 
>         I especially wonder about xgps.  What is its aim?  I can not
>         imagine that the goal is to be a complete DPS backend, that seems
>         to much work and would duplicate a big part of the DGS system.
>         
>         The impression I get (confirmed by an old post in the archives) is
>         that xgps is a temporarily solution.
>         
>         But if it is a temporarily solution is it worth it to put
>         better font support in it?   At any rate, a
>         description of the direction xgps is going is appreciated
>         (and should perhaps be included in the documentation).
> 

I also think that xgps is a temporary solution, but one that will last
for a whole while.
Even if there will be a full working display postscript based solution,
there will be the need for a GNUstep frontend to work with a X-Server
that does not support display postscript.
BTW some weeks ago Ralph Levine took over the maintenance of Ghostscript
and one of the things he put on his working list was display postscript.
So if you have any questions in that area, you should get in contact
with him.

> 3.  During experimenting with my T1-xgps version (gstep-core-0.6.6)
>         I noticed various problems with text drawing.
>         - Text draw at the wrong position,
>                 I know my code is wrong, but even the X11 font support
>                 has this problem, although less noticable.
>         - Scrolling in the Edit.app shows some refreshing problems.
>         How is it in the latest versions?  If nothing is really changed
>         I will try to make a nice bug report ;-) or fix it.
> 

There are a lot of problems left with text formatting and display in
NSText and the layout mechanism. I am working on them, but there has
been only little progress in that area. But still you could check with
the latest CVS version. If the problem is still there, fix it in that
code.

> 4.  If T1 font support is worth while, how about Truetype fonts
>         with freetype2?  Because if we are going to use T1Lib I
>         would want to keep the X11 font support.  And if
>         we support two font engines, why not three?
>         
>         I am not really knowledgable about the differences between all
>         these fonts.  So there could be lots of reasons not to include
>         Truetype fonts?
> 
> 

I based the font support for xgps on the X-Server, so that if there is a
Postscript module loaded (or a Truetype module) all the fonts provided
by that, are supplied to GNUstep. Of course, we don't get all the
specific information from that fonts, only what the X-Server hands on,
but we get what we currently need. There is this great FreeType project
(htttp://www.freetype.org) that will provide access to different fonts
for all applications (An older version is included in XFree 4.0).
Perhaps we could use their interface for all the specialized font
support. For xgps I think that our current solution will be good enough
until we switch over to use Pango (htttp://www.pango.org) in a few
years.

A better Postscript support will also be needed for GNUstep as a whole.
Currently we have split up the backend on that line, but we will need
Postscript for printing in all the GUI code. Some minimal Postscript
support (not Display Postscript, no windows interaction) will be needed
for that. So any work you do will benefit all backends.

> 5.  If I start implementing I will probably have a lot of questions
>         about the desing of xgps and gui. (I have the nextstep docs
>         at hand but that does not always help)  So is this the
>         appriopriate forum?
> 

The GNUStep Developer mailing list <address@hidden> will be more
appropriate for those questions.


> 6.  I got some crashes in the message lookup functions.  (sarray or
>         something like that.)  During sending -release to my
>         new FontInfo object.  If I put a dummy -release in the
>         class it does not happen anymore.  Ideas anyone?

This sounds like a memory management problem. Perhaps you are trying to
free memory that has already been released.

Greetings Fred





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