[OpenLayers-Dev] Exception in OpenLayers.Layer.Grid.removeBackBuffer

[Tim-Hinnerk Heuer]

Just looking some more into my code as well. Is it possibly to do with the
fact that there is a small amount of time that there is no base layer for
the map object I'm using? Maybe I do need to change my application code and
it's not something that should be fixed on the OL side of things. I set the
base layer manually with map.setBaseLayer(myBaseLayer) which is where the
error occurs.

Maybe I need to clean up that bit of code...

Thanks for all the input so far!

On Thu, Mar 15, 2012 at 10:58 AM, Tim-Hinnerk Heuer <th.heuer at gmail.com>wrote:

> Hi Andreas,
>
> Just looking in the source, I see what you mean:
>     /**
>      * Method: clone
>      * Create a clone of this layer
>      *
>      * Returns:
>      * {<OpenLayers.Layer.WMS>} An exact clone of this layer
>      */
>     clone: function (obj) {
>
>         if (obj == null) {
>             obj = new OpenLayers.Layer.WMS(this.name,
>                                            this.url,
>                                            this.params,
>                                            this.getOptions());
>         }
>
>         //get all additions from superclasses
>         obj = OpenLayers.Layer.Grid.prototype.clone.apply(this, [obj]); //
> POINTS TO Grid
>
>         // copy/set any non-init, non-simple values here
>
>         return obj;
>     },
>
> but
>
>     /**
>      * APIMethod: clone
>      * Create a clone of this layer
>      *
>      * Parameters:
>      * obj - {Object} Is this ever used?
>      *
>      * Returns:
>      * {<OpenLayers.Layer.Grid>} An exact clone of this
> OpenLayers.Layer.Grid
>      */
>     clone: function (obj) {
>
>         if (obj == null) {
>             obj = new OpenLayers.Layer.Grid(this.name,
>                                             this.url,
>                                             this.params,
>                                             this.getOptions());
>         }
>
>         //get all additions from superclasses
>         obj = OpenLayers.Layer.HTTPRequest.prototype.clone.apply(this,
> [obj]);
>
>         // copy/set any non-init, non-simple values here
>         if (this.tileSize != null) {
>             obj.tileSize = this.tileSize.clone();
>         }
>
>         // we do not want to copy reference to grid, so we make a new array
>         obj.grid = []; // THIS IS WHAT YOU MEAN, RIGHT?
>         obj.gridResolution = null;
>
>         return obj;
>     },
>
> I don't know how to figure out the problem quickly. I might just have to
> leave the fix as is for now, but this might be good to keep in the back of
> our minds in case we stumble upon this problem again.
>
> Cheers,
> Tim
>
>
> ++Tim Hinnerk Heuer++
>
>
> Twitter: @timhheuer
> Blog: http://www.thheuer.com
>
>
>
> On Wed, Mar 14, 2012 at 9:14 PM, Andreas Hocevar <ahocevar at opengeo.org>wrote:
>
>> The clone method does not clone the grid, so it is not affected by the
>> state of any images in the grid, and it also does not clone any
>> backbuffer related properties. So the issue must be a different one.
>>
>> Andreas.
>>
>> On Wed, Mar 14, 2012 at 8:36 AM, Tim-Hinnerk Heuer <th.heuer at gmail.com>
>> wrote:
>> > Just guessing here:
>> > Maybe the state of a layer changes when the tiles finish loading to
>> > something more consistent that can be cloned and maybe the <img>
>> element is
>> > in a different state or not even there while it is loading? I seem to
>> > remember something like that when I was doing the VideoWMS. Correct me
>> if
>> > I'm wrong.
>> >
>> > Thanks,
>> > Tim
>> >
>> > On Wed, Mar 14, 2012 at 8:28 PM, Eric Lemoine <
>> eric.lemoine at camptocamp.com>
>> > wrote:
>> >>
>> >> On Wed, Mar 14, 2012 at 8:08 AM, Andreas Hocevar <ahocevar at opengeo.org
>> >
>> >> wrote:
>> >> > The only occasions I could think of that could potentially make
>> >> > this.backBuffer both non-null and not a child of this.div is when a
>> >> > layer is cloned during tile loading
>> >>
>> >> I had thought about this too. But I'm still failing to understand how
>> >> cloning can lead to this state. Do you mind elaborating a bit? Thank
>> >> you.
>> >>
>> >>
>> >> --
>> >> 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
>> >> http://www.camptocamp.com
>> >
>> >
>>
>>
>>
>> --
>> Andreas Hocevar
>> OpenGeo - http://opengeo.org/
>> Expert service straight from the developers.
>>
>
>
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