AutoCAD supports different events that allow you to monitor changes to the application environment or drawings.
There are three types of events in AutoCAD:
- Application level events respond to changes in the AutoCAD application and its environment. These events respond to the opening, saving, closing and printing of drawings, creation of new drawings, issuing of AutoCAD commands, loading or unloading of ARX and LISP applications, changes to system variables, and changes to the Application window.
- Document level events respond to the changes of a specific document or its contents. These events respond to the addition, deletion, or modification of objects, activation of a shortcut menu, changes in the pickfirst selection set, changes to the Drawing window, and regeneration of the drawing. There are also document level events for the opening, closing, and printing of a drawing, and the loading or unloading of ARX and LISP applications from the drawing.
- Object level events respond to the changes of a specific object. Currently there is only one object level event. It is triggered whenever an object is modified.
Subroutines that respond to events are called
event handlers and are executed automatically each and every time their designated event is triggered. Information contained in events, such as the drawing name in the
BeginOpen event, are passed to event handlers through parameters.
Note: Both VBA and AutoLISP support the use of events. However, AutoLISP refers to events as reactors and requires the use of specialized functions that begin with the prefix VLR-*. You can learn about the VLR-* functions in the AutoLISP Developer's and Reference guides.