[OpenLayers-Users] zIndexing across multiple vector layers

[dalsinao]

Hi again,

Thanks a lot for your answers, they have been really very helpful and I've
managed to solve my problem.
Below I added a couple of comments to your comments to explain what I've
done.

Thanks again to both of you,
David

>
>Hi,
>
>On Tue, Feb 17, 2009 at 11:26 AM, dalsinao <dalsinao at yahoo.es> wrote:
>> Ok, here is what happens in my case:
>>
>> I get two layers from a WFS server on my map (let's say layer_A and
>> layer_B). These layers contain point geometry features that I display on
>> the
>> map using an external graphics.
>> I have added the singleroot patch (ticket #1666) to be able to select
>> features from any of these WFS (vector-based) layers. When a feature is
>> selected, I open a separate window showing the feature properties.
>>
>> It happens in some occasions that features from layer_A and features from
>> layer_B are at the exact same location.
>> For these situations, I've added some code to create a popup menu that
>> appears on right-click and allows the user to choose which feature he/she
>> wants to check (the features to choose from may belong to layer_A or
>> layer_B).
>
>Wait: the SVG/VML event model will just return the feature that is on
>top. So what you are doing here must be something like in the
>selectBox method of Control.SelectFeature.
>

Yes. In fact, I use code I found in patch mf_selectcontrol.patch (ticket
#434) to calculate which features intersect at the location of the top
feature that has been selected.

>> When a feature is selected, I want the externalGraphic used to display
>> the
>> feature to be moved forward, so the user can see the one that is
>> selected.
>> In this cases, playing with the z-index does not help, since the features
>> may belong to different overlays.
>
>At this point you already know which feature is selected. I see two
>ways to bring it to the top:
> * determine the layer (feature.layer) and move the layer on top of
>the other (e.g. using map.raiseLayer)
> * move the selected feature to a separate (temporary) layer which is on
> top
>


This is just the answer I was looking for :-)
I've finally implemented the option of moving the containing layer to the
top (through map.raiseLayer).
This option seems to work, so I will not try for the time being the other
ones (moving the selected features to a separate layer on top or merging all
WFS data sources in one layer), unless there is some good reason to go for
them, which I don't see at the moment, do you?



>> So, this is my question. What should I do in order to put features from
>> one
>> layer on top of features from another one? Both layers are of
>> OpenLayers.Layer.WFS type, and I have applied the singleroot.5.patch to
>> the
>> OL source code.
>
>You cannot move layers from one layer on top of another layer without
>changing layer order or moving the feature to a layer above.
>
>An alternative would be to merge both WFS data sources into one layer.
>
>Andreas.
>


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