code: function() {
          this.matrix = this.getMatrix();
          if (this.matrix) {
              if (this.matrix.topLeftCorner) {
                  this.tileOrigin = this.matrix.topLeftCorner;
              }
              if (this.matrix.tileWidth && this.matrix.tileHeight) {
                  this.tileSize = new OpenLayers.Size(
                      this.matrix.tileWidth, this.matrix.tileHeight
                  );
              }
              if (!this.tileOrigin) { 
                  this.tileOrigin = new OpenLayers.LonLat(
                      this.maxExtent.left, this.maxExtent.top
                  );
              }   
              if (!this.tileFullExtent) { 
                  this.tileFullExtent = this.maxExtent;
              }
          }
      }
docs: Method: updateMatrixProperties
  Called when map resolution changes to update matrix related properties.