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From: oeschi@netmbx.UUCP (Johann Deutinger)
Newsgroups: comp.os.msdos.programmer
Subject: Re: Word for Windows and DOS idle interrupt (INT28)
Message-ID: <1537@netmbx.UUCP>
Date: 16 Dec 90 11:37:37 GMT
References: <1522@netmbx.UUCP> <1990Dec13.220804.1611@vax5.cit.cornell.edu> <5094@trantor.harris-atd.com>
Distribution: comp
Organization: netmbx, Berlin, West Germany
Lines: 45

In article <5094@trantor.harris-atd.com>, sonny@charybdis.harris-atd.com (Bob Davis) writes:
> In article <1990Dec13.220804.1611@vax5.cit.cornell.edu> hd7x@vax5.cit.cornell.edu (Sanjay Aiyagari) writes:
> >In article <1522@netmbx.UUCP>, oeschi@netmbx.UUCP (Johann Deutinger) writes:
> >> I am developing a TSR using Tesseract (which seems to be a very useful
> >> product) to do some background processing from time to time. It even works
> >> well together with Windows 3.0 with one exception: when I use Word for
> >> Windows no DOS idle interrupts (INT28) occur. Tesseract needs them to poll
> >> my TSR for background processing. Other Windows applications (Write,
> >> Pagemaker, CorelDraw ...) don't cause this problem. Any help for me?
> >
> >Isn't it only necessary to check for INT 28's only if the DOS busy flag is set?
> --------------------------------------------
> 
> If the DOS busy flag (sometimes called the InDOS flag) is set, sometimes it
> is only set because DOS awaits keyboard input (i.e., DOS is at command prompt)
[lines deleted]
> 	But, perhaps, with such software the InDOS busy flag will indicate
> that DOS is NOT busy and therefore one need not even check for an interrupt
> 28h to know that DOS can safely be re-entered.
> 	From my reading on the subject, I have concluded that DOS can 
> safely be re-entered with ANY Int21h DOS function if the InDOS flag indicates 
> DOS not busy. If you know this not to be universally true, please tell me.

[lines deleted...]

There seems to be a minor misunderstanding: my background software (which
is actually used to talk to our intelligent fax card) relies on being
activated through the INT28 hook of TeSseRact, i.e. when DOS waits for
keyboard input or in other I/O busy situation, it does an INT28. This
in turn gives me the chance to do some background processing. If no INT28
occurs (as in Word for Windows) I don't become called from anywhere. All
other Windows application I have don't cause that. TeSseRact additionally
calls INT28 on BIOS keyboard wait, this does not help in Windows which
does not use the BIOS for keyboard I/O. In WfW, as soon as I pull down
one of the menus, INT28 calls do occur, they don't show up as long as I
am in the editing Window. A solution for that is very important to me
because otherwise I could not send or receive faxes during WfW editing.

Johann


-- 
oeschi@netmbx.UUCP     | Johann Deutinger
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