From: Andreas Beck <becka@rz.uni-duesseldorf.de>
  To  : ggi-develop@eskimo.com
  Date: Mon, 17 May 1999 21:50:38 +0200

Re: Some though about raster operation.

> > No, LibGGI2D is an extension and the reason for extensions is to allow 
> > acceleration of stuff that is beyond the libGGI core.  The core was
> > kept very basic on purpose, so it could be implemented on the widest
> > array of display systems and extensions would have something generic to
> > build on.
> BS]  What is the purpose of the libGGI core ? 

To be the smallest subset that makes implementing higher primitives possible
at a somewhat decent speed when there is no specialized implementation
available.

We drew the line at DrawLine, which is the most complex function in the core
LibGGI.

> Why then 2 blit function are in the core ? 

? You are talking about Copybox and CrossBlit ?

They serve completely different purposes. Copybox is intra-visual, and
sometimes needed for implementing higher primitives like
glyph/texture-caching.

CrossBlit allows to transfer data between visuals which is included
to make working with multi-visual setups feasible.

> I don't understand the underlying logic. 
> Could someone explain me which operation goes where and why ?

Everything which isn't in LibGGI yet and does not _have_ to be there
for some reason (like when it deals with mode/target negotiation or similar)
should not go there.

Many many apps do not even need the stuff that already is in the core
LibGGI. The LibGGI core is kind of the lowest common denominator of
common drawing libs.

It is totally painless to implement any addition as an extension, so
we should group every additional set of capabilities that belongs together
into an extension.

> 	What I find odd, is that some subroutine are obviously generic (like
> the one we are talking about) but are considered as specific.

They are specifically optimized, though the optimization level is
pretty low. There still is a generic fallback in generic-stubs.

CU, ANdy

-- 
= Andreas Beck                    |  Email :  <andreas.beck@ggi-project.org> =