How do I make an external ?

[Alex Rice]

On Wednesday, July 30, 2003, at 11:36  AM, Jez wrote:

> I want to make an external for Revolution to access a few of the
> functions provided in User32.dll. I do have experience of visual C
> programming. I found a directory "External SDK" in my old 1.1.1
> Revolution directory, but nothing under 2.0, and I don't understand
> what's in there anyway. Are there any guidelines anywhere ?

Hi, I am not an expert at writing externals, but I have been in the 
same boat as you recently. Information on writing externals is very 
scarce. Here are some suggestions:

1) The "External SDK": look at external.c mainly. This is your primary 
reference. It's not commented very well so you gotta guess what's going 
on. Look at the associated .rev stack. It has two apps in the external: 
Game of Life, and Image Compositing. Why it's not included with RR 2.0 
I would like to know.

2) Post questions to this mailing list. A few people here have been 
coding externals in C for years.

3) _Hypertalk Script Language Guide_ by Apple Computer, in Appendix A, 
has the closest thing I can find to a documentation of the externals 
API. The calling interfaces are changed, but the function names are the 
same. Unfortunately there are more Pascal examples than C examples.

4) RR said a tutorial on writing externals is in the works. Right RR 
:-)?

5) So web searches for XFCN and XCMD. XFCN stands for "external 
function", a transcript function handler that's implemented in native 
code. XCMD is "external command" or a transcript command handler that's 
implemented in native code.

Hope this helps,

Alex Rice, Software Developer
Architectural Research Consultants, Inc.
http://ARCplanning.com