Browser with multiple line selection
Inherits from Browser
The Multi_Browser class is a subclass of Browser which lets the user select any set of the lines. The user interface is Macintosh style: clicking an item turns off all the others and selects that one, dragging selects all the items the mouse moves over, and shift + click toggles the items. (This is different then how Forms did it.) Normally the callback is done when the user releases the mouse, but you can change this with the when property.
See Browser for methods to add and remove lines from the browser.