[ab] lispbuilder-sdl API changes

[Luke J Crook]

This is a quick update on how I am currently butchering the 
lispbuilder-sdl API's. We have discussed most of these changes on this 
list but I am finally getting around to implementing what we discussed. 
Here is the summary:

1) Automatic CFFI finalization when foreign objects go out of scope.
2) Making the lispbuilder-sdl API's more lispy (contentious issue)
3) Having three layers of abstraction.

I'll start with (3): I have already implemented the lower two of the 
three abstraction layers.
   - The lowest tier contains the 'raw' CFFI bindings and 
re-implementation of C macros in Lisp. These are contained in the 
'lispbuilder-sdl-cffi' package.
   - The second tier, 'lispbuilder-sdl-base' contains most of the macros 
and functions that have traditionally resided in the 'lispbuilder-sdl' 
package in the 0.8 release. For example, WITH-SURFACE, WITH-RECTANGLE, 
WITH-EVENTS, BLIT-SURFACE, READ/WRITE-PIXEL etc. The main changes in the 
API's at this level (i.e lispbuilder-sdl -> lispbuilder-sdl-base) are 
that the new API's accept foreign pointers instead of VECTORs for 
rectangles and colors. In addition this layer no longer makes use of the 
default global variables, *default-surface*, *default-color* etc. These 
must be passed as parameters to the functions. Surprisingly the new API 
is very similar to the old API in that the existing examples require 
very minor changes to get working. I made these modifications because 
the current API was quite inefficient. Vectors were being converted to 
and from foreign types and on each call to the CFFI bindings. I noticed 
this when I was trying to speed up pixel access for Anthony (blame 
Anthony for this change ;) )

   - The third tier that I am now working on is CLOS based. It has to be 
because of (1) above. More on this later.

For (2): I have manually gone though all the SWIG generated CFFI 
bindings in 'lispbuilder-sdl-cffi' and performed a lispification on 
almost everything. This means that SDL_BlitSurface is now 
sdl-blit-surface. Why, I hear you scream? Well, Emacs automatically 
expands (s-b-c to sdl-blit-surface with the C->TAB combination. It's 
cool and it really speeds up coding. I haven't gone completely overboard 
and wrapped constants in '+', e.g. +blah+ as this I don't like.

For (1): This layer will be entirely CLOS based. This will be the 
'lispbuilder-sdl' layer. The CFFI finalization methods require that 
foreign objects be wrapped in a class in order to fire the necessary 
clean up routines when the Lisp object is garbage collected. The 
advantage is that coding using this layer should now be a lot easier as 
a lot less messy WITH-* macros are required.

Let me know what you all think.
- Luke