[mapguide-internals] CSS sprited legend images - RFC

[Zac Spitzer]

this post got a bit lost in discussion,

the ajax viewer performs better because it only renders a subset of
large legends,
abbreviating them [ .... ] fusion tries to render them all and ends up
DOSing the browser

CSS sprites for the legend is sorely needed

What's the technical requirements?

GetLegendImageStrip
GetLegendCSS

Proper http cache semantics for those operations

cached in the session repo? generated when requested,
cache invalidated after changes to the run time map,
but only after re-rendering and comparison of new and old
has changes

z

---------- Forwarded message ----------
From: Jason Birch <Jason.Birch at nanaimo.ca>
Date: Sat, Apr 4, 2009 at 9:03 AM
Subject: [fusion-dev] RE: [mapguide-users] Fusion and Themed Layers - usability
To: "mapguide-users at lists.osgeo.org" <mapguide-users at lists.osgeo.org>
Cc: "fusion-dev at lists.osgeo.org" <fusion-dev at lists.osgeo.org>,
'MapGuide at lists.osgeo.org, Internals Mail List'
<mapguide-internals at lists.osgeo.org>


Heh,

Yeah, I can see how that would be unmanageable.  I wouldn't be
surprised if your use case strains fusion to the level that it's not
workable for the current version or for 2.1.  I'm surprised it works
with the AJAX viewer, but maybe the viewer has a different strategy
for managing legend images.

Ideally, MapGuide would support a GetLegendImageStrip operation that
Fusion could then use with CSS sprites to reduce (in your case,
dramatically) the number of requests to the server.  I believe that
there may be functionality for this in MapServer layer types in Fusion
2.0, but I don't think there is in MapGuide.  Bob Bray put in a ticket
for this functionality a _long_ time ago, but unfortunately I don't
think any work has been done on it:
http://trac.osgeo.org/mapguide/ticket/22

I think that there is a partial measure that could be done in Fusion
to improve the situation somewhat.  Currently, Fusion does a
reasonable job of caching images; it only requests a new legend image
once per scale range context switch.  However, the initial request is
done using the exact current scale.  If the request instead used a
fixed value within the scale range (bottom + x?) then the images could
be better cached by the browser.  If MapGuide sent cache headers (last
modified, based on the layer definition?) this would also help.

Any Fusion or MapGuide devs have thoughts on this?

Jason

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-- 
Zac Spitzer
Solution Architect / Director
Ennoble Consultancy Australia
http://www.ennoble.com.au
http://zacster.blogspot.com
+61 405 847 168