So on thinking this over, it has occurred to me something that might<br>
be a good solution to this problem:<br>
<br>
A sort of blend of the OpenLayers.Layer.Markers layer and the <br>
OpenLayers.Layer.WMS.Untiled Layer. <br>
<br>
Basically, the problem now is this:<br>
<br>
Let's say you are using OpenLayers.Layer.Text and load 1000<br>
features/markers (like Andy is doing)<br>
<br>
Each and every one of those markers gets added to the DOM, <br>
even though given the current view, maybe only 20 or 30 of them<br>
are visible. <br>
<br>
The genius idea behind WMSUntiled is that it loades a tile that is <br>
[variably] larger than the current map extent, and only loads the data<br>
for that tile... and it is not until the user changes the extent (by panning<br>
or zooming) such that the original tile no longer covers the entire map<br>
extent that the layer has to reload data. <br>
<br>
Well, we could really do the same thing for markers, right? Keep all <br>
the markers in the OpenLayers.Layer.Makers.markers[] array and then<br>
each time we need to load a tile, scan the markers array to see which<br>
of them fall inside the bounds. <br>
<br>
...which of course leads me to think that we could do some restructuring<br>
of the layers classes. I have for long felt that WMS/Untiled.js was a bit off. <br>
<br>
First of all, it *is* tiled. It's just that there's only ever *one* tile. So to start <br>
with, it might make more sense to call it SingeTile or UnGridded or <br>
something along those lines. <br>
<br>
Furthermore, if we are going to have an UnGridded WMS, why shouldn't<br>
we have an UnGridded WFS? <br>
<br>
Obviously, the class rearrangements would require a significant amount<br>
of work and rewriting and testing, etc. <br>
<br>
For Andy's problem, writing a simple UnGridded/SingleTiled Marker layer <br>
would not be particularly difficult. <br>
<br>
Is anyone out there interested in any of this?<br>
<br>
Erik<br><br>
<br>
<br><div><span class="gmail_quote">On 10/18/06, <b class="gmail_sendername">Erik Uzureau</b> <<a href="mailto:euzuro@gmail.com">euzuro@gmail.com</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Dear andy,<br><br>How many text markers are we talking about here? It is a known limitation<br>of browsers that they cannot handle displaying (and then moving around)<br>large numbers of Div DOMElements... especially with IE.
<br><br>If you can tell us a little more about what you're trying to do, maybe we can<br>help you better. :-)<br><br><br>--Erik<br><br>On 10/18/06, andy <<a href="mailto:aborruso@tin.it">aborruso@tin.it</a>> wrote:<br>
> Dear all,<br>> I need an advice. I must use a marker layer for its tooltip feature. I<br>> have used "OpenLayers.Layer.Text", I have had what I need but I have<br>> slowness when I have a lot of text markers.
<br>> Are the other methods to create markers faster? Which is fastest?<br>><br>> Thank you,<br>><br>> a<br>><br>> P.S. In the openlayers home page there is an inaccessible link:<br>> <a href="http://openlayers.org/presentations/foss4g2006/examples/">
http://openlayers.org/presentations/foss4g2006/examples/</a><br>> _______________________________________________<br>> Users mailing list<br>> <a href="mailto:Users@openlayers.org">Users@openlayers.org</a><br>>
<a href="http://openlayers.org/mailman/listinfo/users">http://openlayers.org/mailman/listinfo/users</a><br>><br></blockquote></div><br>