[OpenLayers-Users] MapTips

[Eric Lemoine]

Hi Matthew,

I see two main options:

 - use a WFS layer. Your hotspots are displayed as markers or vector
geometries in a WFS layer on top of the WMS layer. If you pan the map
new hotspots will be automatically downloaded from the WFS service.
You can easily have popups on mouse over these hotspots. WFS Examples:
<http://www.openlayers.org/dev/examples/wfs.html>. Popup example:
<http://www.openlayers.org/dev/examples/select-feature-openpopup.html>.

 - use GetFeatureInfo-type mechanism. As the mouse goes over the WMS
layer, Ajax requests are sent to some search service (possibly
WMS/GetFeatureInfo). As opposed to the solution you mentioned in your
email, there's no preload here, but I think it can be fast enough if
things are optimized on the server. See an example here:
<http://www.openlayers.org/dev/examples/getfeatureinfo.html>

Hope this helps,
--
Eric

On Dec 5, 2007 10:41 PM, Matthew Atkins <Matthew.Atkins at loyola.com> wrote:
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> OpenLayers Users,
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> I am currently replacing an ArcIMS HTML Viewer application with a new
> OpenLayers interface which will be a great leap from what they have in
> general navigation usability. I think that I won't have much trouble
> replacing almost all of the other functionality (Identify, Measure, Select,
> etc.) provided by the ArcIMS application but there is one that I am not sure
> of the best way to handle in order to port over the same effect and
> response... and that is a feature we call MapTips.
>
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> If you are not familiar with the term "MapTips" then here is a brief
> description – in the ArcIMS application only one layer can be
> selected/active at a time. We have a button that toggles MapTips on or off
> for the selected layer. When it is turned on the user can just mouse over
> any feature from that layer on the map and a pop up (DIV) shows attribute
> data for the specific item they are hovering over. It's basically a quick
> identify on a feature but the information has been preloaded so it is very
> quick and easy to use.
>
>
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> If you are not familiar with ArcIMS web sites then here is some information
> on how they accomplish this – by default, at least for older (pre 9.2)
> versions of ArcIMS, only a single image is returned at any given time to
> draw the entire map. So, to create MapTips, a spatial query is done for the
> current extent and selected layer ... from the results of this query an
> image map is created for the current map image thus making the "hot spots"
> that will capture the mouse over event a trigger the showing of the
> attribute info in the DIV.
>
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> So, using OpenLayers instead of the generic ArcIMS HTML Viewer poses a
> challenge with the tiles/grid of the map images. At least it means that we
> can't use exactly the same methodology as before, but maybe I could take the
> same idea and make an image map for each tile that comes in from my WMS
> service. Or, maybe I could have markers appear on all the features of the
> selected layer when MapTips are toggled on so they can handle the mouse over
> events. But, how will that be handled dynamically? When the user navigates
> outside of the current view and new features come into view they need to
> have a marker appear on them. Are the more alternatives that might be a
> better way to handle this scenario?
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> I was just curious to see if anyone has attempted something like this with
> OpenLayers already or if anyone has thoughts on the best areas of OpenLayers
> to utilize or hook into to make this functionality work in a graceful
> manner.
>
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> Thanks in advance for any and all comments,
>
>
>
> Wally Atkins
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