Re: Proposal. Looking for feedback, interest, etc.

[Alexander Malmberg]

> Hello all!
>   I¹m working on that GNUstep based distribution, SimplyGNUstep.  Since the
> goal of the distro is to be very user friendly (developer friendly too) I
> would like to introduce some new aspects to the GNUstep ³system².
>   The main thing I¹d like to do is to create a new, non-X11 backend which
> uses a common postscript based imaging model.  Instead of X11 I want to
> interact with the kernel framebuffer in a similar fashion as OS X does.
> That is, have a light weight WindowServer process and (my own addition) a
> DisplayManager process (for multiple displays).
>   The way I would like to do this is by creating a very generic postscript
> interpreter and implement it as a shared library.  I¹m thinking that this PS
> lib would only be able to render to an in memory pixmap, nothing more.  That
> way, the exact same code could be used for both printing and the display.
> By using shared memory the graphical result can be transferred to the
> display or a printer device interpreter/converter.

back-art works by rendering to a buffer, blitted to the screen by using
normal X calls, and optionally XShm (I assume that the gslib backend
works similarly). There's _highly_experimental_ proof of concept (ie.
it's mostly broken and unimplemented and not even remotely usable) code
for doing it with an abstract display server at
http://w1.423.telia.com/~u42308495/alex/backart/rds-0.0.1.tar.gz . I'm
not working on it at the moment, but it shows how it could be done.

I fail to see how this would help printing, though.

>   I¹ve been reading the PS and DPS references and I know creating a PS
> interpreter is no easy feat.

The backend interface is not a pure PS/DPS interface, it's a mix of
PS/DPS and PDF/Quartz. 'Interpreter' is pushing it.

> The VM is complicated and the generic path
> based graphics is no joke to code (especially to make it run fast).  I¹m not
> proposing a completely new code-base be started, rather, I was thinking of
> grabbing the GPL ghostscript and ³cutting and pasting² it into this new
> project.  AFAIK the license allows this (feedback?)

AFAIK, yes, but cutting and pasting would be an ugly solution. You might
want to have a look at how gslib works (or simply use it; it sounds
pretty much like what you want).

>   Since the PS lib would be very generic, it is plausible it can be used in
> the x11 backend as well.  Is anybody else interested in this?
> More specific, is anybody interested in helping?

There are several x11-based backends (-xlib, -xdps, -art, -gslib), and
another backend based on the back/Source/x11 code is possible. However,
this does sound very similar to the gslib backend.

- Alexander Malmberg