New version of gslib backend available

[BALATON Zoltan]

Hello,

A new version of the gslib patch is available again at
http://goliat.eik.bme.hu/~balaton/gnustep/gnustep-back-gslib-4.patch.gz

It is still very experimental, but some important things are now
implemented (although some bugs remain). As usual, it is NOT yet for the
general public, but I would be interested in feedback from developers.

To try it you need:
* GNU Ghostscript 7.05 or newer
 - To fix a bug in Ghostscript apply this patch:
   http://goliat.eik.bme.hu/~balaton/gnustep/ghostscript-image.patch
 - Use the following makefile:
   http://goliat.eik.bme.hu/~balaton/gnustep/makefile
   (To build do 'make STDDIRS; make libgslib.a')
* Patch is against cvs of Aug 1 10:21 CEST
 - Apply to back, set GHOSTSCRIPTDIR in config.make
 - configure with --enable-graphics=gslib
 - You have to figure out and set the correct dspformat in
   GSGSContextX11.m:_setupDisplayDevice to match the config of your display
   (for explanation see GHOSTSCRIPTDIR/src/gdevdsp.h,
   for hints try the --GNU-Debug=GSGSCallbacks debug channel)

Changes since last version:
* Implemented image handling (still has bugs though):
 - Compositing operators (compositerect, composite, dissolve)
 - Data source images (NSDrawBitmap)
* Stub implementation of text handling
 - Stub for show operator (does nothing as font handling is still missing)
* Some other easy operators are now implemented
 - fill, eofill, arc, arcn, arct, curveto, rcurveto

Known bugs: (but soulutions nevertheless welcome :-)
* Colors in images are garbled (probably the ghostscript gstate is not
  initialised correctly)
* Sometimes some images are flipped, one is mixed up. (could this
  be a bug in the gui?)
* Not all drawing appears when it should (currently things are rendered to
  a memory buffer and copied to the window when flushGraphics is called)
* Some lines are 1 pixel off (this is probably a rounding difference between
  ghostscript and the gsc/xlib backend)

Missing functionality:
* Font handling (this is a tough one, probably the easiest way is to use
  freetype (the ghostscript developers are also work on this))
* Implement missing operators (this should be easy)
* Port to other platforms (should be easy as ghostscript is portable)
* Use hardware acceleration (this may involve implemeting a ghostscript
  driver or patching existing ones which is moderately hard)
* The FIXME-s...

Greetings,
BALATON Zoltan