ActionScript for Flash MX: The Definitive Guide, Second Edition

This is the Title of the Book, eMatter Edition

Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.

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Chapter 13: Movie Clips

• When manually created instances are initially loaded, code in their timeline and

onLoad() event handlers executes according to the Load Order set in the Publish

Settings of a Flash document—either Bottom Up, which is the default, or Top

Down.

For example, suppose we have a timeline with two layers, top and bottom, where

top is above bottom in the layer stack. We place clip

X on layer top and clip Y on

layer bottom. If the Load Order of the document is set to Bottom Up, then the

code in clip

Y will execute before the code in clip X. If, on the other hand, the

Load Order of the document is set to Top Down, then the code in clip

X will exe-

cute before the code in clip

Y. This execution order applies only to the frame on

which X and Y appear for the first time.

• Once loaded, all instances of a movie are added to an execution order, which is

the reverse of the load order; the last instance added to the movie is always the

first to have its code executed.

Use caution when relying on these rules. Layers are mutable, so you should avoid

producing code that relies on their relative position. Strive to create code that exe-

cutes safely without relying on the execution order of the clips in the stack. We can

avoid some of the issues presented by the execution stack