[OpenLayers-Dev] Grid-style loading of Markers

Eric Lemoine eric.lemoine at camptocamp.com
Thu Feb 11 07:45:56 EST 2010

On Thursday, February 11, 2010, Matt Williamson <MatthewDW at gmail.com> wrote:
> Eric,
> Ah, thanks for this--you hit on part of my misunderstanding, that not all strategies in trunk are clustering strategies. I didn't realize that the BBOX strategy actually loaded more data from the server.
> So I experimented with the BBOX strategy, and unfortunately it doesn't really fit my needs, for two reasons.
> One (the lesser), I have a problem with data density--if I just select the top (most "interesting") 150 points in the BBOX, they may all be in one place. Consider Salt Lake City, Utah, which is a large city in the middle of mountain wilderness. If I center the map showing Utah, I get 150 points in Salt Lake City, and none in the mountains--I'd like to be able to display points in data-sparse areas, even if they're lower priority points, when there is room. My tile generation routine uses a computationally expensive mechanism to fill those gaps--but if I can pre-generate them, then there's no real-time cost.
> Two (the greater), the BBOX strategy does not load more points when zooming in. If the map starts centered on Utah, then the user zooms out to the whole U.S., then zooms back in on Texas, it doesn't load new points, because the zoomed-in BBOX is still within the old zoomed-out BBOX. Since the new viewport is still within the last gathered dataset, it does not attempt to get more features. If there's a way to configure the BBOX strategy so this is not the case, please let me know!

set resFactor to 1, look at the API doc to understand that option.

> So, am I to assume from your comments that the BBOX strategy is still a valid option? Do you happen to know if it still even works with 2.8 or will with 2.9? And/or, that functionality hasn't been merged into some other object in the mainline trunk or otherwise made obsolete by some other new functionality? I just don't want to invest in obsolete or orphaned code, especially if there's something better.

The BBOX strategy is in 2.8 and trunk, the Grid strategy is just in
the vector-behavior sandbox as noone as shown interest in pursuing the
work on that Grid strategy.


Eric Lemoine

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