Introduction to Behaviors

We continue to receive a fair number of questions related to
Behaviors in IMS Web Engine (see the first User Question). It is
not surprising since it is probably the most complex component
in the software. I consequently thought that it would be useful to
republish a past article on this topic. Even if you don't use Web
Engine, you may be interested to see some of the
Events that can be created with it,

Both IMS Web Spinner and IMS Web Engine include two
simple behaviors that can be assigned to your Objects. These
behaviors can set an Object's visibility while the page is first
loading, after it has loaded or on a mouse over or mouse leave
event. These Behaviors are a useful way to create several special
effects that toggle an Object's visibility.

IMS Web Engine includes the ability to create far more complex
behaviors based on many different interrelated events. The
effective use of these Behaviors is probably the most complex
aspect of learning to use IMS Web Engine.

We have tried to simplify several common uses for Behaviors by
incorporating them into the IMS Web Engine Wizards. These
include the creation of drop menus, strobe effects, and the
management of several animation effects. Mastering the use of
the Behavior dialog however, will give you the ability to create
complex interactive web pages including DHTML games,
business presentations and educational courseware.

A Behavior works by switching between an 'Active' and a 'Not
Active' state. Don't be misled by the terms. There is nothing
intrinsically different between the two states other than what you
decide to assign to them. In other words, an Object could just as
easily be invisible when 'Active' as when 'Not Active'.

The Behavior is composed of two components. The first is an
Event that triggers a Behavior 'Active' or 'Not Active'. The
second is an Action that will be performed when the Behavior
enters either of these two states. The user defines a Behavior by
deciding what the trigger mechanisms are and what actions will
be performed as the Behavior switch between the two states.

As an example, we can use a simple Mouse Over Behavior to
make an Object Visible and Invisible.


The trigger events in this example are the mouse moving over
and off the Object. By default, the Object starts in a 'Not Active'
state. As the cursor is moved over the Object, it triggers the
Object into its 'Active' state. As the cursor moves off the Object
it triggers its 'Not Active' state. The Behavior's 'Actions' are to
make the Object 'Visible' when it is triggered into its 'Active'
state and 'Invisible' when triggered into its 'Not Active' state.

As I mentioned previously, there is no intrinsic difference
between an Object's 'Active' and 'Not Active' state. Figure
is20fig2 illustrates this with two examples. Example 1 will make
an Object Visible as the mouse mo
ves over it. Example 2 does
the reverse.

This example is of course very simple and can be more
efficiently done by setting an Objects Visibility in the Object
Editor. The principle for more advanced Behaviors remains the
same. The difference lies in the types of Events that can trigger a
Behavior and the Actions that can be performed by the Behavior.

The example at  is20fig3.htm  illustrates some of the Behavior dialogs
including Triggers and Actions that can be applied to a Behavior.
User Triggers include Mouse Over, Mouse Select or a keyboard
character. Dynamic triggers include Time, when two Objects intersect
or don't intersect, or when an Object's internal value equates to a
simple test. An event can also be triggered by another Object when
its Events are triggered.

There are many Actions a Behavior can perform when an Event
is triggered. These include setting an Object's visibility, starting
or stopping its Action or Sound Component if it has one, or
triggering the Event of another Object's Behavior. Actions can
also include applying a mathematical formula to any Object or
performing a
Metamorph operation on an Object. Despite the big
word, this simply means changing one or more of an Object's
Components. An example would be switching an Objects Action
component that traces a rectangle to an Action component that
traces a polygon.

These operations may seem complicated when taken in their
entirety. When looked at individually however, they are far
easier to understand.

The Virtual Mechanics Behaviors demo illustrates two simple  
Behaviors to make a series of Text Objects visible as the mouse
or  the Bird Object moves over them. There are many other
examples in  the demo section and at the
dhtml magic site
including an educational interactive map.. You can also look at
the Web Engine tutorials if you have not already done so for
more information on creating Behavior.

"IMS Web Tips" ISSN 1488-7088
© Copyright 2000 Virtual Mechanics

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