Path: utzoo!attcan!utgpu!watmath!att!dptg!rutgers!cs.utexas.edu!csd4.csd.uwm.edu!mailrus!ncar!ico!auto-trol!marbru
From: marbru@auto-trol.UUCP (Martin Brunecky)
Newsgroups: comp.windows.x
Subject: Re: rubberbanding with Xlib
Message-ID: <260@auto-trol.UUCP>
Date: 30 Aug 89 22:33:21 GMT
References: <123886@sun.Eng.Sun.COM> <2449@srava.sra.JUNET>
Reply-To: marbru@auto-trol.UUCP (Martin Brunecky)
Organization: Auto-trol Technology, Denver
Lines: 29

> Implement rubberbanding ....

I'v seen some advices so far. What I do is as follows (and it DID
generate good results on VS2000 running FT of DECWINDOWS long time
ago. However, you will NEVER track the pointer EXACTLY, there is
always a delay due to the roundtrip. We solve this by using NONE
cursor (which is unfortunatelly missing in the standard cursors, you have
to create one by hand using XCreatePixmapCursor... with a "blank"
pixmap 1x1 pixel).

1) we set pointer motions hint in the window event mask so that we
   don't get swamped with hundreds of motion events. Or in Xt,
   specify compress_motion in core part to TRUE.

2) when we get a motion event, we call XQueryPointer. It costs a round-trip,
   but we get the true LAST pointer position.

3) we compare position to the previous one = no move, skip it

4) we try to do the undraw-draw in one protocol request (using Xor)
   if possible - i.e. using XDrawSegments. Till about 50 (?) segments
   you get good results. Above that, blt from pixmap may be better.


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Martin Brunecky, Auto-trol Technology Corporation,
12500 North Washington Street, Denver, CO-80241-2404
(303) 252-2499                                        ncar!ico!auto-trol!marbru
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