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From: pt93mg AT pt DOT hk-r DOT se (Mats Grahm)
Newsgroups: comp.os.msdos.djgpp
Subject: Hooking on interrupts
Date: 20 Aug 1995 05:43:41 GMT
Organization: College University of Karlskrona-Ronneby
Lines: 39
Distribution: world
Reply-To: pt93mg AT pt DOT hk-r DOT se
Nntp-Posting-Host: neptunus.pt.hk-r.se
To: djgpp AT sun DOT soe DOT clarkson DOT edu
Dj-Gateway: from newsgroup comp.os.msdos.djgpp

I'm quite new to protected mode programming, and got some problems when trying
to redirect keyboard interrupts to my program.

I have a keyboard handler from a book that I have tried to convert to pm.
Basicly I just commented out all "far" keywords, and replaced the getvect()
and setvect() calls with their go32 equvivalents, doing my best to follow
the instructions in the info file:

_go32_dpmi_seginfo myhandler;

handler.pm_offset = (int) KeyIntHandler;
handler.pm_selector = _go32_my_cs();
_go32_dpmi_allocate_iret_wrapper(&handler);
_go32_dpmi_set_protected_mode_interrupt_vector(9, &handler);


This works, but to be able to restore normal keyboard handling, I want to save 
the old handler. Should I use the protected or real mode version of 
	_go32_dpmi_get_???_mode_interrupt_vector() ?

I have tried both ways. As long as I only restore the keyboard at the end of
the program, it doesn't seam to matter, I suppose go32 does some cleanup. 

But when I temporarily restore to the old handler to allow libgrx GetMouseEvent()
to handle simultaneous keyboard and mouse events, I get a segmentation fault.
If I treat the vector as realmode it happens in some end() function, if I treat
it as pm it happens in int33(). I asume they both are called from somewhere inside
the mouse library, since the keyboard is lost when this happens I can't get any
further information from gdb. Only thing to do is to reboot.

So my two questions are:
	Should I treat the old keyboard interrupt vector as real or protected?
	Both ways I get segmentation faults in GetMouseEvent(). Any suggestions why? 

Thanks in advance for any help!

Mats