[OpenLayers-Dev] using overlays with tilecache

[Christopher Schmidt]

On Fri, Jan 19, 2007 at 01:47:48PM -0500, Frank Porcelli wrote:
> Dev team -
> 
>  
> 
> I have run into an issue with OpenLayers that I'm hoping someone may have
> experienced and can provide a work around. When using TileCache with
> OpenLayers to display multiple layers of data, I'm noticing that when
> changing zoom levels or panning to a location outside of the initial extent
> the overlay tiles come back pink. On the initial load, both layers load fine
> and display no problem. The initial "zoom in" also works fine. However, when
> panning to another part of the map, using the overview map or pan tool,
> overlay images that are outside the initial extent come back pink. If I zoom
> out to full exent I also notice that the number of overlay tiles does not
> marry up with the number of basemap tiles. This could partially explain why
> the pink tiles. Has anyone run into this issue before? This appears to be a
> bug in OpenLayers. If so, any suggestions on what could be the cause would
> be appreciated.

Frank:

The "Pink Tile Syndrome" has been reported by a variety of users,
usually on data which is not pre-cached. I haven't personally run into
the problem much, but we've recently (2.3/SVN) added functionality to
help reload tiles which suffer pink tile syndrome.

To enable this functionality in OpenLayers 2.3, simply set the variable:

OpenLayers.IMAGE_RELOAD_ATTEMPTS = 2;

or something similar. 

Does doing this help you at all?

You might also check your webserver log for evidence of failure -- the
data might be improperly returned, or something similar. If you can find
a failing server, you might be able to reduce the need for reloads.

If this doesn't help you, please reply and we can investigate further. 

Regards,
-- 
Christopher Schmidt
MetaCarta