Triggered in a destination object when the mouse pointer is over the object.
The DD_KEYBOARD_STATE, DD_MOUSE_STATE, DD_X_AXIS and DD_Y_AXIS properties contain the keyboard and mouse statuses, and the mouse pointer's coordinates relative to the object.
The DD_DATA_AVAILABLE and DD_READ_DATA methods can be used.
The DD_ALLOWED_ACTIONS property contains the actions that the source object allows the user to perform.
At the end of the event, the DD_ACTION_DROP property should contain the action that would be performed if the user released the mouse button at that location. This value is used by the system to determine the mouse pointer shape.