You can define a selection event control function for rectangle selection or polygon selection, or for both.

A rectangle selection event control function is called whenever rectangle selection is enabled and a rectangular selection area has been created by clicking and dragging the mouse (to indicate two diagonally opposite corners) on an SVG map.The function is called immediately after the selection of the rectangle is completed and the mouse key is released. The function name is specified with the onrectselect attribute in the map request (see map_request Attributes).

A polygon selection event control function is called whenever polygon selection is enabled and a polygon-shaped selection area has been created by clicking and dragging the mouse at least four times on an SVG map, with the last click on the same point as the first click to complete the polygon. The function is called immediately after the selection of the polygon is completed. The function name is specified with the onpolyselect attribute in the map request (see map_request Attributes).