[OpenLayers-Users] ModifyControl Select/Delete Vertex?

[Robert Smart]

Hi,

Nice work! I could see this as being very useful to many people.

A few comments though.

This also picks up clicks on virtual vertices, which would need to be changed.

This there a way to define a style for the selected vertex? 

Is there a way to store a reference to the selected vertex in the modify feature control? So that I could allow a user to select a vertex and then if they choose to delete it, I can just pull out a reference to it in the code from the modify feature. I suppose this could also just be a deleteSeletectedVertex function on the modifyFeature control too.

Is there a way to deselect the the vertex too? So if I click on it and it changes its style to the ‘selected’ style, I can then click on it again to deselect it?

Thanks,

Rob Smart


From: Alexandre Dubé 
Sent: Thursday, February 28, 2013 5:07 PM
To: Robert Smart 
Cc: openlayers-users at lists.osgeo.org 
Subject: Re: [OpenLayers-Users] ModifyControl Select/Delete Vertex?

Hi Rob,

  This small example should give you the idea I had in mind: 
    http://dev5.mapgears.com/openlayers/2.12/examples/modify-feature-vertex-click.html

  You'll notice I extended the ModifyFeature control class. It's recommended to do that than modifying the source code (in fact, you should never edit the source code of a lib).

  What do you think ?

HTH,

Alexandre


On 13-02-28 09:42 AM, Robert Smart wrote:

  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 

         

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Alexandre Dubé
Mapgears
www.mapgears.com
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Mapgears
www.mapgears.com

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