Events

When the operator interacts with a GUI, an event occurs. For example, when the operator:

• types something into a field on a form,

• moves the cursor into a window,

• presses down a mouse button,

• moves the mouse with button down,

• lets the button up.

The events are queued in a time-ordered queue. The application software services this queue: it gets the next event, determines the object of the event (for example, form, gadget, menu) and the event type (for example, enter, leave, select, unselect, popup, and so on), deduces appropriate actions and carries them out. When one event is completed, the software looks for the next event.