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Next: Director Example 1: Simple Up: Multimedia Programming:Scripting (Lingo) Previous: Types of Scripts

Messages and Events

To run the appropriate set of Lingo statements at the right time, Director must determine what is occurring in the movie and which Lingo to run in response to specific events.

Director sends messages to indicate when specific events occur in a movie, such as when sprites are clicked, keyboard keys are pressed, a movie starts, the playback head enters or exits a frame, or a script returns a certain result.

Handlers contain instructions that run when a specific message is received. The handler's name begins with the word on followed by the message name. When an object receives a message that corresponds to a handler attached to the object, Director runs the Lingo statements within the handler. For example, a handler named on enterFrame that is attached to a frame runs when the playback head enters the frame.

Most common events that occur in a movie have built-in message names. See the following categories in the Lingo Dictionary for the built-in messages that describe events:

You can also define your own messages and corresponding handler names. A custom message can call another script, another handler, or the statement's own handler. When the called handler stops executing, the handler that called it resumes. Director can send a custom message from any location. The message is first available to handlers in the script from which the message was sent. If no handler is found, the message is available to movie scripts. If more than one movie script contains a handler for the message, the handler in the movie script that has the lowest cast member number is executed. A custom handler name must:

Using Lingo keywords for handler names can create confusion. Although it is possible to explicitly replace or extend the functionality of a Lingo element by using it as a handler name, this should be done only in certain advanced situations. When you have multiple handlers with similar functions, it is useful to give them names that have similar beginnings so they appear together in an alphabetical listing, such as the listing displayed by the Find Handler option in the Edit menu.

Director follows a definite order when sending messages about events that occur during the course of a movie. When the movie first starts, events occur in the following order:

When Director plays a frame, events occur in this order:

When a movie stops, events occur in this order:

A movie can contain more than one handler for the same message. Director manages this situation by sending the message to objects in a definite order.

The general order in which messages are sent to objects is as follows:

When a message reaches a script that contains a handler corresponding to the message, Director executes the handler's instructions.

After a handler intercepts a message, the message doesn't automatically pass on to the remaining locations. (You can use the pass command to override this default rule and pass the message to other objects.) If no matching handler is found after the message passes to all possible locations, Director ignores the message.

The exact order of objects to which Director sends a message depends on the message. See the message's Lingo Dictionary entry for details about the sequence of objects to which Director sends specific messages.

You can place handlers in any type of script. However, the following are some useful guidelines for many common situations:

next up previous
Next: Director Example 1: Simple Up: Multimedia Programming:Scripting (Lingo) Previous: Types of Scripts
Dave Marshall