[OpenLayers-Users] Mouse Drag Coordinates

[Eric Lemoine]

On Friday, October 30, 2009, Dave Thomas <davidt at integeo.com> wrote:
>
> Hi Everyone,

Hi


>
> Hi have what I though would be a simple task but its proving to be a little more frustrating than I anticipated.
>
> What I need to do is get the coordinates for pan events so that I know the coordinates of when the drag started and when it ended. The logical way to do this as far as I thought was to listen for the mousedown (or movestart) and mouseup (or moveend) events and get the coordinates from there. Its not behaving the way I anticipated though. I've tried a whole bunch of different ideas - four of which I'll list here. Surely one of these is close.  I think the first two are the closest.
>
> I'd very much appreciate any input that may help.
>
> Many Thanks
> Dave
>
>
>
> Method 1. Not all Events are recevied and of the ones that are I can't get the coordinates from all of them.
>
> click: yes
> mousemove: yes
> mouseup: yes
> mousedown: no
> movestart: yes - but coordinates recevied are NAN
> moveend: yes - but coordinates received are NAN
>
>
>    var options =
>    {
>        ... other settings....
>
>       eventListeners: {
>          "movestart": doEvent
>       }
>    };
>
>    function doEvent(event) {
>       var obj = this.events.getMousePosition(event)


getMousePosition works with browser events only.


>       alert(obj);
>     }
>
>
> Method 2. Same results as Method 1
>
>
>    map.events.register("mousemove", map, function(e) {
>       var position = this.events.getMousePosition(e);
>       alert(position);
>    });
>
>
>
>
> Method 3. Clicks are called but not mousedowns.
>
>
>    OpenLayers.Control.Click = OpenLayers.Class(OpenLayers.Control, {
>       defaultHandlerOptions: {
>          'single': true,
>          'double': false,
>          'pixelTolerance': 0,
>          'stopSingle': false,
>          'stopDouble': false
>       },
>
>       initialize: function(options) {
>          this.handlerOptions = OpenLayers.Util.extend(
>          {}, this.defaultHandlerOptions
>             );
>          OpenLayers.Control.prototype.initialize.apply(
>             this, arguments
>             );
>          this.handler = new OpenLayers.Handler.Click(
>             this, {
>             'click': this.doClick,
>             'down': this.doDown,
>             'mousedown': this.doMouseDown
>          }, this.handlerOptions
>             );
>       },
>
>       doClick: function(e) {
>          alert('click');
>       },
>       doDown: function(e) {
>          alert('down');
>       },
>       doMouseDown: function(e) {
>          alert('mouseDown');
>       }
>    });
>
>
> Method 4.  Callbacks are only received if Navigation is deactivated.
>
>
>    OpenLayers.Control.Drag = OpenLayers.Class(OpenLayers.Control, {
>        defaultHandlerOptions: {
>            stopDown: false
>        },
>
>        initialize: function(options) {
>            this.handlerOptions = OpenLayers.Util.extend(
>                {}, this.defaultHandlerOptions
>            );
>            OpenLayers.Control.prototype.initialize.apply(
>                this, arguments
>            );
>            this.handler = new OpenLayers.Handler.Drag(
>                this, {
>                    'down': this.doDown,
>                    'up': this.doUp,
>                    'move': this.doMove,
>                    'done': this.doDone
>                }, this.handlerOptions
>            );
>        },
>
>        doDown: function(e) {
>            alert('down');
>        },
>       doUp: function(e) {
>            alert('up')
>       },
>       doMove: function(e) {
>            alert('move');
>        },
>       doDone: function(e) {
>            alert('done');
>        }
>    });

implementing a specific control based on a Drag handler is what I'd go
with. You can look at the DragPan control to know how to use the Drag
handler - I tend to think that you could rely on the "move" and "done"
callbacks only. Now regarding the conflict with the Navigation
control: have you tried making sure your control is activated *before*
the Navigation control?

Cheers,

-- 
Eric Lemoine

Camptocamp France SAS
Savoie Technolac, BP 352
73377 Le Bourget du Lac, Cedex

Tel : 00 33 4 79 44 44 96
Mail : eric.lemoine at camptocamp.com
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