Selection and Data Picking

When graphical items are drawn to a window, it is often useful to be able to click the mouse on a certain location and request a list of the items that are displayed at that particular location. In IDL, this is called selection. Because IDL object graphics are retained in memory, they can be uniquely identified by their individual object references, and therefore can be reported as having been selected.

In many cases, it is also useful to be able to request the data value of the object at the user-selected location. In IDL, this is called data picking.