User`s guide

Retrieving Event Information

In this section.. .

“Introduction” on page 7-7

“Event Structures” on page 7-7

“Example: Accessing Data in the Event Log” on page 7-9

Introduction

Each event has associated with it a set of information, generated by the

toolbox and stored in an event structure. This inform ation includes the event

type, the time the event occurred, and other event-specif ic inform ation. While

a video input object is running, the toolbox records event information in the

object’s

EventLog property. You can also access the event structure associated

with an event in a callback function.

This section

• Defines the information in an event structure for all event types

• Describes h ow to retrieve information from the

EventLog property

For information about accessing event information in a callback function, see

“Creating and Executing Callback Functions” on page 7-12.

Event Structures

An event structure contains tw o fields: Type and Data.Forexample,thisisan

event structure for a trigger event:

Type: 'Trigger'

Data: [1x1 struct]

The Type field is a text string that specifies the event type. For a trigger

event, this field contains the text string

'Trigger'.

The

Data field is a structure that contains information about the e ve nt.

The composition of this structure varies d epending on which type of event

7-7