Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!usc!ucsd!ucbvax!bloom-beacon!LARRY.MCRCIM.MCGILL.EDU!mouse
From: mouse@LARRY.MCRCIM.MCGILL.EDU
Newsgroups: comp.windows.x
Subject: Re:  Making X work on Interactive 386/ix
Message-ID: <9012031413.AA01486@Larry.McRCIM.McGill.EDU>
Date: 3 Dec 90 14:13:06 GMT
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 35

> We have [...hardware summary...], ... but, the mouse drags are at a
> lag of 3-4 seconds behind!

This may not be the fault of your hardware; it may be a problem with
your clients.

Some clients animate mouse drags badly.  When mouse motions can be
generated faster than the thing being animated can be drawn, the naive
code produces animation which lags the mouse, and lags the mouse more
and more as the mouse is moved.  (If the mouse is left still, the
animation eventually catches up.)

This problem will often go unnoticed, because when everything is
running on nice fast machines with a nice fast network between them,
the time to update the animation is tiny compared to the interval
between mouse events, for any common animation (eg, window outlines).
But throw in a couple of slow gateways, or a machine which draws
relatively slowly for some reason, or a hardware/server combination
which produces mouse events unusually quickly, and you have a recipe
for bad lags when mouse dragging.

This problem arises when clients stupidly update the animation on
receipt of each MotionNotify event, without paying any attention to all
the other MotionNotify events that are sitting in the queue.  This is
precisely what PointerMotionHintMask was created for; everybody doing
this sort of mouse dragging should learn how to use it.  (Some clients
"fix" the problem by doing a stream of QueryPointer requests instead.
This sort-of cures the problem when it's due to slow drawing or
fine-grained mouse tracking, but actually makes netowrk-caused problems
worse.  It's not the right fix.)

					der Mouse

			old: mcgill-vision!mouse
			new: mouse@larry.mcrcim.mcgill.edu