See demo scene 509
Starting version 2.3 WMSK provides an useful API which you may call to initiate a rectangular selection. Just call:
map.RectangleSelectionInitiate(callback, rectangleColor, rectangleLineColor);
Once you call this function, the user will no longer be able to drag round the map but still can make a rectangle selection, clicking and dragging over an area.
Each time the rectangle size changes, the callback function is called passing the Rect coordinates and a boolean indicating if the mouse button has been released hence the selection has ended.
You can customize the rectangle selection passing a fill color and a color for the animated border line.
map.rectangleSelectionInProgress returns true if a rectangle selection is occuring. map.RectangleSelectionCancel will abort current rectangle selection.