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DoInitAction

Tag Info
Tag Number: 
59
Tag Type: 
Action
Tag Flash Version: 
6
Unknown SWF Tag: 
This tag is defined by the Flash documentation by Adobe
Brief Description: 

Actions to perform the first time the following Show Frame tag is reached. All the initialization actions are executed before any other actions. You have to specify a sprite to which the actions are applied to. Thus you don't need a set target action. When multiple initialization action blocks are within the same frame, they are executed one after another in the order they appear in that frame.

Tag Structure: 

Tag Structure: 
struct swf_doaction {
	swf_tag			f_tag;		/* 12 and 59 */
	if(f_tag == DoInitAction) {
		unsigned short	f_action_sprite;
	}
	swf_action		f_action_record[variable];
};

The DoAction tag will be used to execute a set of actions in place. Usually, actions are used on buttons to add interactivity to the SWF movies. In version 1 you had only one dynamic branch (WaitForFrame). In version 4 you can test many different things such as a position, angle or sound track cursor position. Since version 5, SWF has a complete scripting language supporting string and arithmetic operations.

The DoInitAction tag is used when a sprite needs to be initialized. These actions are carried on the sprite only once. These are outside of the given sprite and will reference the sprite so all the actions are automatically applied to the sprite without you having to do a SetTarget.

The following describes the data in the DoAction and DoInitAction tags:

The f_action_sprite is a reference (identifier) to the sprite which will be initialized with the given actions.

The f_action_record is an array of actions terminated by an End action.

The following is a list of all the actions supported by SWF format. The Version tells you what version of Flash player you need in order to use the given action (otherwise it is likely to be ignored or worse, make the player crash). Note that Macromedia defines all the actions as being part of version 3 and over. Thus, any action mark as being available in earlier versions (version 1 or 2) may in fact not be (though the DoAction and DefineButton tags were part of version 1!!!)

The Length (Stacked) column specifies the length of the data following the property (only with the action ID is 0x80 to 0xFF) and what will be pushed onto the stack. All the expressions work as in polish notation: push the parameters, then execute an order that uses the data from the stack. The actions that do not push anything on the stack have nothing written between parenthesis.

The Data & Operation column specifies what data follows the action and what the operation is. If there is no data and no operation, then n.a. is used. The data will be described as a list of fields as in the other structures described in this document. The operations will be written as closely as possible to a C like operation (though strings are managed in a much different way than C!) Anything which is popped from the stack will be given a letter and a digit. The digit represents the count or position and the letter the type of the data (a count of 1 represents the first pop, a count of 2 represents the second pop, etc.) The following column (Comments) will explain how the operation uses the data when appropriate.

The data types used are as follow:

    Short Type
    a any type
    b boolean
    f foat
    i integer
    n(1) numeric (integer or float)
    o(2) object (as in C++)
    s string
    t array or table of values
    v variable - pushes multiple values on the stack

    (1) when I don't know whether an integer or a float should be specified I will use 'n' as well. This should be correct most of the time anyway.
    (2) an object reference can be obtained by evaluating the name of that object; thus GetVariable("carrot") will return a reference to the carrot object.

The following lists all the actions by name. Those that have the comment (typed) operates taking the type of its arguments in account as defined in ECMA-262 Section 11.6.1 (arithmetic), 11.8.5 (comparison), 11.9.3 (equality) which you can certainly find somewhere on the Internet. Version 3 is available here: ECMA-262 V3.0. The functions which are not typed will behave by (1) trying to transform parameters in values, then perform the operation with numbers only or (2) when strings cannot be transformed in values, perform a string operation.

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