agree at carltonfields.com wrote:
> 
> How, then, does the calling/signalling prim-code communicate parameters to the callback? 

>From the "The Do-It-Yourself Guide to Squeak Primitives"
(http://www.create.ucsb.edu/squeak/DIYSqPrims.html) --

"You can also trigger Smalltalk semaphores from C primitives; see John
Maloney's SoundPlayer class or Siren's
PrimMIDIPort for examples. This is by far the best way to implement
"call-backs" from C to Smalltalk--have the Smalltalk
application class pass down a semaphore to the VM and then start a loop
process that waits for the semaphore and handles
it asynchronously (If you're really clever, you can even create events
and post them in Squeak's event input queue.)"

The way I "pass arguments" is to have the data cached in the VM, and
have the waiting process make another "fetch" prim call. In the case of
the MIDIPort input, the code outline looks like the following:

	On start-up (port open), call a prim. and pass it a semaphore number
(that's 
		registered as external)
	Start a wait process in Smalltalk that waits on that semaphore
	At some later time (in response to a primitive or to external
activity), signal 
		the semaphore from the VM.
	The Smalltalk wait process makes a prim. call to get some data and
waits again

-- 
stp

Stephen Travis Pope | stp at create.ucsb.edu |
http://www.create.ucsb.edu/~stp