Respect layer projection if it equals the map projection

[ahocevar]

With several projection codes available for the same projection, but WMS servers that do not support all of these, it makes sense to respect the layer projection for WMS GetMap requests when they equal the map projection.

Let's say our map is in EPSG:3857, the official web mercator EPSG code, but it uses a layer that only supports the equal EPSG:900913 projection, we should be able to do:

var map = new OpenLayers.Map("map", {
    projection: "EPSG:3857"
    /* ... */
});
var layer = new OpenLayers.Layer.WMS("mywms", "/path/to/wms",
    {layers: "world"},
    {projection: "EPSG:900913"}
);

[ahocevar]

proof of concept - no tests yet

[ahocevar]

Tests pass in Safari 5. Thanks for any review.

[ahocevar]

with tests; also works for unknown projections now

[tschaub]

Thanks for taking this on. I think this looks like a great solution. I had previously thought about supporting projection aliases (as a property on a projection object), but I think handling it with a null transform is a good solution.

[tschaub]

respect layer projection if it equals map projection

[tschaub]

Two minor changes in my patch:

• I changed the ; to a , in Projection.js to avoid setting the global equals.
• I made it so window.Proj4js is deleted if it didn't exist before in the Projection.js test so other tests running after it aren't fooled.

I think this looks like a very solid solution to handling projections with different aliases. Thanks for the great patch.

[ahocevar]

r10869