design (+ usage)

(this is for now just a design document and not describing the actual program.)

slutpet makes use of s7 scheme as a scripting language.
(this, by the way, is why the program takes a weirdly long time to compile --
s7.{c,h} contain the entire s7 scheme interpreter, over 100,000 lines.)
if you don't know scheme,
   a) don't worry, it's pretty simple, and
   b) sorry in advance.

c source files:

sp.c:	main entry, exit, event/render loops

a pet is implemented by setting the variable 'pet' to
an alist (is this the correct term?) which contains some values.
setting the pet variable should handle this automatically,
but various hooks can then be set, which will be executed
whenever a certain event has happened.

list of variables:
pet:		the pet that the program will use. this is a list of cons that define the pet.
		TODO: maybe this should be a macro that sets other variables.

pet-name:	string containing the pet's name.

list of hooks:
pre-init-hook:	before anything has happened at all; right after s7 has been initialised.
		this is also before any init files have been read
post-init-hook:	when the window has been set up and things are ready to happen.
		the current pet should be set and initialised by this point.
tick-hook:	every program tick. the pet's drawing information should be set
		here so it can be rendered.
TODO: figure out what to do about event hooks
pre-quit-hook:	the program is about to exit, no de-init things have been done yet.
post-quit-hook:	everything (except, obviously, the s7 interpreter) has been de-initialised.

list of functions:
(load-image path):	set up a new image, with the data taken from the given path.
	    		this will return the a list of cons pairs with the image data,
			in a form that can be used in the pet variable.
(free-image image):	free heap-allocated data in image.

list of c-types:
pixmap:			the data created from stb-image.