User`s guide

8 Using Events and Callbacks
8-8
Retrieving Event Information
In this section...
“Introduction” on page 8-8
“Event Structures” on page 8-8
“Accessing Data in the Event Log” on page 8-10
Introduction
Each event has associated with it a set of information, generated by the toolbox and
stored in an event structure. This information includes the event type, the time the event
occurred, and other event-specific information. 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 how 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 8-12.
Event Structures
An event structure contains two fields: Type and Data. For example, this is an 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 event. The composition
of this structure varies depending on which type of event occurred. For information about
the information associated with specific events, see the following sections:
• “Data Fields for Start, Stop, Frames Acquired, and Trigger Events” on page 8-9