[OpenLayers-Users] ModifyControl Select/Delete Vertex?

[Robert Smart]

Great! I’m using version 2.12. 

Thanks,

Rob Smart

From: Alexandre Dubé 
Sent: Thursday, February 28, 2013 1:59 PM
Cc: openlayers-users at lists.osgeo.org 
Subject: Re: [OpenLayers-Users] ModifyControl Select/Delete Vertex?

Sure, I'd be glad to help.  What version do you use ?

Alexandre


On 13-02-27 12:36 PM, Robert Smart wrote:

  Hi, 

  Thanks for a really in depth answer. It really explains it well.

  Unfortunately my javascript skills are pretty basic at the moment, so a lot of that went over my head!


  I like the sound of the vertexselection event on the vector layer class. Could you give me a few more hints about how this might work?


  Or even better give me an example bit of code :)


  We would need to be able to access the vertex index of the selected vertex, and i guess there would have to be a method of removing the vertex from the feature, which would trigger a redraw of the feature on the map. 


  We would have to also be able to define a style for that selected vertex too, and i suppose add some error trap to ensure that we can't select a virtual vertex?



  Thanks again,


  Rob




  On 27 Feb 2013, at 13:51, "Alexandre Dubé" <adube at mapgears.com> wrote:


    Hi Rob,

      This would indeed be a nice feature to have.  Looking at the ModifyFeature control, I think this could be easily accomplished with minor modifications.

      If we look at the ModifyFeature control, it creates a DragFeature control to allow dragging the vertices around.  When you "mouse hover" a vertex feature, a callback function is triggered because it was defined here :
        https://github.com/openlayers/openlayers/blob/master/lib/OpenLayers/Control/ModifyFeature.js#L267

      That's the callbacks for the OpenLayers.Handler.Feature object the drag control needs to interact with features on the map.  The drag control defines its callbacks method in the featureCallbacks object :
        https://github.com/openlayers/openlayers/blob/master/lib/OpenLayers/Control/DragFeature.js#L119

      and here's the list of callbacks you can set to a feature handler: click, clickout, over, out, and dblclick.
        https://github.com/openlayers/openlayers/blob/master/lib/OpenLayers/Handler/Feature.js#L30

      So, back in the ModifyFeature control, you could add a 'click' callback function just next to the 'over' one.  Instead of coding what you want it to do directly in the source, just define an abstract function that needs to be overriden OR you could fire an new vector layer event : vertexselected (which would need to be added to OpenLayer.Layer.Vector).

      Whoa, sorry for the long reply :)   In short, try to create a delegate method or event we could register to to do whatever we wanted on vertex selection.

      Does that make sense ?

    HTH,

    Alexandre


    On 13-02-26 11:42 AM, Robert Smart wrote:

      Hi All,

      I'm trying to port some existing functionality into open layers and have 
      managed to get most of it working. I'm just stuck on a seemingly simple 
      task.

      The current code allows a user to highlight a polygon vertex by clicking on 
      it (which changes its colour), so that the user can then press a delete 
      button to remove the vertex.

      Using the modify control I'm able to display the vertices, and even delete 
      them if I click on it and then press 'del' on my keyboard, but this is not a 
      great solution as there is no visual clue as to what vertex has been 
      selected.

      So is there a way to highlight or change the colour of a single vertex the 
      user has clicked on? is there then a way to remove that vertex via code and 
      have the polygon redraw on the screen to suit?

      I think this would actually be quite useful as a standard feature as there 
      are many cases where one might want to select an individual vertex.

      Thanks,

      Rob 

       

_______________________________________________
Users mailing list
Users at lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/openlayers-users



-- 
Alexandre Dubé
Mapgears
www.mapgears.com
_______________________________________________
    Users mailing list
    Users at lists.osgeo.org
    http://lists.osgeo.org/mailman/listinfo/openlayers-users




-- 
Alexandre Dubé
Mapgears
www.mapgears.com


--------------------------------------------------------------------------------
_______________________________________________
Users mailing list
Users at lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/openlayers-users
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/openlayers-users/attachments/20130228/e7f69346/attachment-0001.html>