[OpenLayers-Users] OpenLayers.Layer.XYZ - how to set origin?

[Robert Sanson]

Dear OpenLayers Users

I am trying to connect to a custom tile cache, using OpenLayers.Layer.XYZ

The projection used is EPSG:2193 (New Zealand Transverse Mercator) and the tileOrigin for this service is -1000000, 10000000 (top left)

The extents of the imagery are: [827933.23, 3729820.29, 3195373.59, 7039943.58]

How do I set the tileOrigin on the layer? Is it based on the map maxExtent?

Looking at XYZ.js it has:
/**
     * Method: getXYZ
     * Calculates x, y and z for the given bounds.
     *
     * Parameters:
     * bounds - {<OpenLayers.Bounds>}
     *
     * Returns:
     * {Object} - an object with x, y and z properties.
     */
    getXYZ: function(bounds) {
        var res = this.getServerResolution();
        var x = Math.round((bounds.left - this.maxExtent.left) /
            (res * this.tileSize.w));
        var y = Math.round((this.maxExtent.top - bounds.top) /
            (res * this.tileSize.h));
        var z = this.getServerZoom();

        if (this.wrapDateLine) {
            var limit = Math.pow(2, z);
            x = ((x % limit) + limit) % limit;
        }

        return {'x': x, 'y': y, 'z': z};
    },
    
    /* APIMethod: setMap
     * When the layer is added to a map, then we can fetch our origin 
     *    (if we don't have one.) 
     * 
     * Parameters:
     * map - {<OpenLayers.Map>}
     */
    setMap: function(map) {
        OpenLayers.Layer.Grid.prototype.setMap.apply(this, arguments);
        if (!this.tileOrigin) { 
            this.tileOrigin = new OpenLayers.LonLat(this.maxExtent.left,
                                                this.maxExtent.bottom);
        }                                       
    },


Many thanks,

Robert Sanson