To: Heasley <heasleka AT ptbma DOT usbm DOT gov>
Cc: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: Re: program crashes with mouse movement? 
Date: Thu, 19 Jan 95 18:21:26 +0200
From: "Eli Zaretskii" <eliz AT is DOT elta DOT co DOT il>

> Subsequently, I have turned the mouse cursor off before the disk reads 
> and then turned the mouse cursor on after the disk reads/writes and this 
> seems to stop the crashes (MouseEraseCursor, MouseDisplayCursor).  This 
> seems to make the program work, but I do not necessarily understand why.

This is only a wild guess, but it is usually considered harmful
to mix disk writes and serial communications (in this case, with
the mouse, which is serial, right?).  There even is a tiny TSR
called RTS (look on SimTel/msdos/modem/rts14.zip) which lowers
the RTS bit when disk cache flushes its buffers, so that serial
port won't lose characters due to this.  When you disable the
cursor, the mouse driver stops communicating with the mouse, so
the problem doesn't happen.  This effect might be amplified by
the hardware interrupt handling in DJGPP 1.1x, which leaves
much to be desired.