[mapserver-users] Re: Symbol problem (trunked) using tiled OpenLayers...

[Stephen Woodbridge]

stefanoferri wrote:
> Im sill having problems .... labelcache_map_edge_buffer "-10" remove the
> labels close to the border... but i would like to have these icons... :(...
> Why if i use wms instead of &mode=tile&tilemode=gmap&tile it works fine ?
> thanks
> 

When you use mode=tile, the software has to adjust the extents of the 
the image to fit to a tile. The image that you see in the browser is 
actually many tiles placed side by side.

Because labels are dynamically positioned based on what other stuff is 
being display, there is a possibility for labels to move and there are 
lots of parameters that control some of the position issues with labels 
like:

partial false
position auto

and there are some metadata parameters like labelcache_map_edge_buffer 
and probably some others.

Mapserver does not know what or how it drew the tiles adjacent to the 
one it is currently drawing. For example if you have a lone horizontal 
line that crosses many tiles and each tile draws it, should they all 
label it or only some of them? The way we make this look good is to use 
metatiles, these are large images made up of many tiles that are 
rendered and then chopped into tiles. this way we can draw more like a 
single image WMS and mapserver controls labels based on this large image 
and avoids labeling near the edges so labels to not get truncated 
between tiles that lie on adjacent metatiles.

Mode tile does not give you this option. It is planned to add WMS-C tile 
caching to mapserver 6.0, and in this you would get the ability to use 
metatiles.

Sorry I don't think you can do what you want with mode=tile at the 
moment, but I would defer to others that might be more knowledgeable on 
mode=tile.

-Steve W