[OpenLayers-Users] SPAM-LOW: Re: problem labeling vector features - vertices being labeled too

[Michael Anderson]

Thanks again Eric. Haven't used a context before, but it sounds like exactly 
what I need. I'll give it a try later today.

Mike

----- Original Message ----- 
From: "Eric Lemoine" <eric.lemoine at camptocamp.com>
To: "Michael Anderson" <mike at spatialit.com>
Cc: <users at openlayers.org>
Sent: Thursday, August 20, 2009 2:22 AM
Subject: Re: [OpenLayers-Users] SPAM-LOW: Re: problem labeling vector 
features - vertices being labeled too


On Thursday, August 20, 2009, Eric Lemoine <eric.lemoine at camptocamp.com> 
wrote:
> On Wednesday, August 19, 2009, Michael Anderson <mike at spatialit.com> 
> wrote:
>> Eric is correct. The modifyFeature control is using the select style. 
>> Setting the select style's label to an empty string does remove the label 
>> on the polygon feature being edited. But the vertices are still labeled. 
>> So it is still trying to label the vertices with an attribute value (from 
>> the default style?) and putting the empty string from the select style on 
>> the polygon.
>
> Right. This is because the modify feature control uses the "default"
> render intent for drawing the vertices (and the rotation and drag
> handles).
>
>
>>
>> Gives me an idea for a temporary hack though. I have a function that 
>> finds vertices. I can modify it to add the label attribute to the 
>> vertices and set them to empty strings. That should let me label the 
>> polygon while the vertices appear to not have labels. Should work as long 
>> as adding attributes to a vertex won't cause a problem I don't know 
>> about.
>
> How about using a context, with something like that in your style map:
>
> "default": new OpenLayers.Style({
> label: "${label}",
>  // other symbolizer properties here
> }, {
> context: {
>  label: function(f) {
>  if(f.geometry.CLASS_NAME !=
>  "OpenLayers.Geometry.Point") {
>  return f.attributes.label;
>  } else {
>  return "";
>  }
>  }
>  }
> })
>

even better: have the context function check if the label attribute exists:

    context: {
        label: function(f) {
            return f.attributes.label != undefined ? f.attributes.label : 
"";
        }
    }