[mapserver-users] How do they do that???

[Ed McNierney]

Ross et al. -

Good luck with the DHTML approach.  I have learned the hard way that, in
my case, that actually wasn't a good solution.  I added some features to
TopoZone (interactive coordinate display on mouseover, symbol overlay,
etc.) and I decided NOT to use Java because users had "security
concerns" and didn't allow the use of applets.  I instead implemented
everything in DHTML/JavaScript to avoid that.

I learned two things.  First, most users or organizations that
prohibited Java for "security reasons" felt the same way about
JavaScript.  An amazing number of groups lumped them all together as
"that Java stuff" and I didn't really gain very much.  Second,
DHTML/JavaScript cross-browser compatibility is pure hell.  If you can
constrain your list of supported browsers VERY tightly, and if you're
ready to do more work every time your supported vendors issues a new
release and breaks things, you'll be OK.  But it can be a very painful
process.

As soon as I get around to it, I'm going back to Java and reimplementing
those features (and more) in a Java applet.

	- Ed

Ed McNierney
Chief Mapmaker
TopoZone.com


-----Original Message-----
From: Searle Ross [mailto:Ross.Searle at dnr.qld.gov.au]
Sent: Sunday, November 25, 2001 9:25 PM
To: mapserver-users at lists.gis.umn.edu
Subject: RE: [mapserver-users] How do they do that???


We have developed some frames/DHTML approaches to this. DHTML is used to
give you the box drawing capabilities while the frames take care of
image updates. We originally used the applet based approach but ran into
troubles when some of our target audiences worked in organisations that
didn't permit the downloading of applets. Also the frames based stuff
seems to be a bit more robust. The URL for an example of this approach
is
http://www.dnr.qld.gov.au/resourcenet/land/lris/webgis/burnett/maps/mapf
rame.html

Regards
Ross

-----Original Message-----
From: Stephen Lime [mailto:steve.lime at dnr.state.mn.us]
Sent: Thursday, 22 November 2001 5:23 AM
To: Chip.Hankley at GASAI.Com; mapserver-users at lists.gis.umn.edu
Subject: Re: [mapserver-users] How do they do that???


Well I can speak to landview since I wrote it. In short it uses a small
applet to do the display and mouse event handling and manages all of the
coordinate information using a javascript library. Then I use a public
method of the applet to swap the image being displayed. The image urls
are actually calls to the MapServer (mode=map). This could also be done
using DHTML (i.e. layers) IF you use frames or a single page design with
absolute positioning of layers. Absolute positioning is fine in a frame
with nothing else or if you have a design with nothing that will change
size to the left and above your map. Personally I like the freedom the
applet gives you.

All of my code is available on request, but it really needs more
documentation (like everything else).

Steve

Stephen Lime
Data & Applications Manager

Minnesota DNR
500 Lafayette Road
St. Paul, MN 55155
651-297-2937

>>> "Hankley, Chip" <Chip.Hankley at GASAI.Com> 11/21/01 10:33AM >>>
I've seen a few MapServer apps where, after a navigation event, the
entire
page doesn't reload... only the map window.

for example:
http://maps.dnr.state.mn.us/landview/ 
http://144.92.235.164/orthofinder/ 

How do they do that? Is this using Java? One site uses frames and the
other
doesn't...

TIA

Chip Hankley



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