[OpenLayers-Users] How does a renderer draw features ?

[Alexandre Dube]

Hi Eric,

  I've not been able to work on my little project until recently.  I 
tried what you suggested and and worked fine.  When the mouse is over a 
feature, its color changes without selecting it.  And when the mouse is 
out, it regain its original color.

  Thank you very much for your hint, it helped me a lot.

  If anybody wants to see how I made it, you're welcomed to ask.

Alexandre

Eric Lemoine wrote:
> On Fri, Aug 1, 2008 at 3:48 PM, Alexandre Dube <adube at mapgears.com> wrote:
>   
>> Hi list,
>>
>>    I was wondering something : when we select a feature using a select
>> or modify control, the feature changes its color...  In fact, I saw that
>> it the renderer that draws a feature ( which draw geometry ) using a
>> given style.
>>
>>    My question is : does the renderer actually draw a new feature over
>> the original one or it really changes the color ?
>>     
>
> It changes its color.
>
>   
>> The renderer does not
>> contain any feature, but it can draw features ?
>>     
>
> Yes.
>
>
>   
>>    I'm trying to figure out how it works because I am able to "change"
>> color when my mouse is over a feature without selecting it, but I'm
>> trying to undo the changes as soon as the mouse isn't over anymore and
>> it's not working.
>>
>>    Here's a code snippet :
>>
>>    var drawnGeometry = null;
>>
>>    var styleBlue = OpenLayers.Util.extend(
>>        {},
>>        OpenLayers.Feature.Vector.style['default']);
>>    styleBlue.strokeColor = "blue";
>>    styleBlue.strokeWidth = 4;
>>
>> function changeColorOnOverFeature(e){
>>    // if no feature is selected, then we want to change the color of a
>>    // feature when over it
>>    if (!getSelectedFeature(this)){
>>        if (drawnGeometry != null){
>>            this.renderer.eraseGeometry(drawnGeometry);  // I'm pretty
>> sure this is wrong
>>            drawnGeometry = null;
>>        }
>>        else {
>>            oFeature = this.getFeatureFromEvent(e);
>>            if(oFeature){
>>                this.renderer.drawFeature(oFeature, styleBlue);
>>                drawnGeometry = oFeature.geometry;
>>            }
>>        }
>>    }
>> }
>>
>> // inside my init()
>> oMap.events.register("mousemove", olWFSRoads, changeColorOnOverFeature);
>>
>>
>> Erasing the geometry makes the feature disappear, but it's still in the
>> layer features, with no changes of its geometry and all...  I'm quite
>> sure this is not the best way to do it.  Any clues ?
>>     
>
> You should use a feature handler (Handler.Feature) to detect
> mouseover/mouseout on features. Look at the select feature control to
> understand how to use it.
>
> --
> Eric
>   


-- 
Alexandre Dubé
Mapgears
www.mapgears.com