DWF Viewer and map requests, scale dependent geometry

Joel Carranza jec at gatekeeper.com
Wed Mar 22 18:30:54 EST 2006


The MapGuide client as of version 6.5 did a pretty good job in only asking
for data when it really needed it. More specifically
- turning a layer off, and then back on, did not result in any server
requests. The layer data was cached and reused whenever the layer was turned
on
- Zooming in only slightly (perhaps a click of the zoom wheel) did not
result in any server requests, unless required by layer scale dependencies
- "Zoom to Previous View" often did not result in an any server requests, if
possible
The new DWF viewer does not seem to implement any of this functionality.
When I flip a layer off and on, I see in the Apache logs that I am
downloading the entire layer over again. When I zoom in a little bit, I am
downloading a fresh copy of the entire map! The size and frequency of
requests from the DWF viewer may make deployment in the field (over a
wireless conection) impossible. 
Is this a bug or a feature? 
I am guessing that caching is less feasible when you are serving up scale
dependent geometry (lines are less detailed the further zoomed out you are),
but is there/will there be a way to tune these parameters on a per layer
basis? What if I don't want my geometry simplified? Will this have effects
on DWF viewer caching?

Joel Carranza
Gatekeeper Systems
626-449-3070 x114
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