[gs-devel] Kick-off of ESP/GPL GhostScript merger: X11 output device modularization

[Till Kamppeter]

Hi,

to start the planned merger of ESP and GPL GhostScript I have ported the 
feature of modularization of the X11 output device. Before submitting 
the patched GhostScript do the SVN repositories I want to present the 
patch here.


For what do we need this?
-------------------------

Every Linux distribution ships GhostScript as binary packages. There was 
one problem. If the GhostScript has X11 support built-in you can display 
PostScript and PDF files on the screen but on an X-less server you have 
a lot of disk-space wasting do to the dependency of the GhostScript 
package on the X libraries. If you would leave out the X11 support users 
are not able to display PostScript and PDF files.

Many years ago distros shipped two GhostScript packages, one with and 
one without X. This made maintainability more difficult and wasted CD 
space/download volume.

More or less in 2000 at Mandriva a patch was developed to modularize the 
X11 and the SVGA output devices so that one got two binary RPMs, one 
with the GhostScript core and one with the X11 and SVGA output devices 
in a dinamically linkable library. On servers only the GhostScript core 
was installed and on desktops both the core and the X11/SVGA output 
device libraries. GhostScript auto-detected the presence of the X11/SVGA 
output device libraries and if present it listed the appropriate devices 
in "gs- h" and allowed to use them. This solved the problem without 
wasting any space.


Is this patch stable?
---------------------

This patch I have introduced into ESP GhostScript and there it was for 
many years. Due to the complete printer driver spectrum and the "cups" 
output device all distros use ESP GhostScript by default and as this 
functionality is built by default on Unix/gcc/libdl systems it is 
present on all Linux distros. To me there are no known bug reports on 
ESP GhostScript, Mandriva, and Ubuntu concerning the X11 device 
modularization.

On my port to the current SVN snapshot of GPL GhostScript I have checked 
the ESP GhostScript crasher bugs reported to Ubuntu

https://bugs.launchpad.net/ubuntu/+source/gs-esp/

and they do not get introduced into GPL GhostScript by the patch.


Is the functionality of this patch portable?
--------------------------------------------

Unfortunately, it works only on Unix/gcc systems with libdl, but it does 
not break compilability of the patched GhostScript, as it uses 
conditional compiling.

The new code is only compiled if GS_DEVS_SHARED is set. GS_DEVS_SHARED 
is only set in the src/unix-gcc.mak file (so only on Unix/gcc systems). 
Adding configurability to the configure script would not be a big problem.

Mike Sweet has kept ESP GhostScript also as portable as possible, as it 
is done with GPL GhostScript.


How to get the patch?
---------------------

Download it here:

http://www.linuxprinting.org/download/printing/esp-gpl-ghostscript-merge/ghostscript-8.57-x11-svga-as-shared-library.patch

Apply it with

cd gs
patch -p1 < ../ghostscript-8.15-x11-svga-as-shared-library.patch

and compile as usual.


Tests
-----

I have tested the patch and it works correctly with and without the 
X11.so module being present. Crasher bugs (and many of the other bugs, 
too) reported to Ubuntu

https://bugs.launchpad.net/ubuntu/+source/gs-esp/

do not get introduced by the patch.


I could upload it to the subversion repositories and we can see by the 
regular regression tests whether it does not break anything.

Is there a possibility that I can trigger the regression tests after an 
upload to the SVN or do I have to wait for a cron job?

    Till