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From:	jpg AT cs DOT waikato DOT ac DOT nz (J P Griffiths)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Idea: DJGPP w/windows...
Date:	15 Aug 1995 21:58:13 GMT
Organization:	The University of Waikato
Lines:	47
Sender:	jpg AT waikato DOT ac DOT nz
Reply-To:	jpg AT waikato DOT ac DOT nz
Nntp-Posting-Host:	neptune.cs.waikato.ac.nz
To:	djgpp AT sun DOT soe DOT clarkson DOT edu
Dj-Gateway:	from newsgroup comp.os.msdos.djgpp

Hello fellow DJGPP'ers,

  While I was trying to sleep last night I began to think about how you could use the 
windows API from DJGPP DPMI programs in either windows or win 95.  Here's The idea I came
up with.

NOTE: I have no experience whatsoever in progamming under windows,  so this is just a 
guess at how someone could attempt it.

The main problem seems to be cludging up an interface (in asm) and therefore getting your 
program to call the API by c wrappers which call the windows functions.  This method 
would produce a lot of asm code,  lots of work,  and probably need quite a bit of 
reverse engineering/undocumented stuff to work.

However,  there are (commercial) windows compilers out there that already have this 
functionality built in - they can call any API function they want.  If our DJGPP 
programs could tap that functionality,  then they could use the API.

So why not set up a program (using a commercial windows compiler) that acts as a server,
recieving messages about API calls and managing them for a client program?

One way of implementing this would be:
The windows compiled program boots the DJGPP image as a dos box process.  They 
communicate through some interrupt mechanism.  When the DJGPP program wants to call the API,
it calls a c wrapper which triggers the interrupt (with a code for the API call),  and 
waits for a signal that indicates the API call was succesful.  The windows program opens 
and manages windows for the DJGPP program,   giving the illusion that the DJGPP program is
in control of the window.  

All this requires to work is a way of sharing a small part of memory space between the 
programs so that signals/parameters may be passed in it.  If you wanted to get really 
technical, you could make the windows server handle more than one DJGPP process at a time,
by requiring all programs to "register" themselves to the server, and using a unique ID 
number (which was passed back) to indicate which DJGPP process required which services.

This method would be slower than standard windows programs but might work under NT and 
95.  As soon as DJGPP can produce windows programs with API functionality,  my 
prediction is that it will rapidly become the most popular dos/windows compiler.

Thoughts?  Ideas?  Comments?  Problems?

Looking forward to your replies...

    Jon.
    (jpg AT cs DOT waikato DOT ac DOT nz)

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