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

[Eric Lemoine]

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