Howto:Nasal in scenery object XML files

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For introductory information about Nasal, you'll want to check out Nasal scripting language.

(As of 05/2009, this is work in progress and entirely based on [1]).

There's now support for embedding Nasal code (scripts) into object XML files.

This can be used for 'intelligent' objects -- such as for example special lighting features, specific lighthouse signals, things that couldn't be done with animations alone.

The code is run as soon as the tile loader decided to load the model. It can use listeners and timers and so run as long as it wishes. If the object is removed from memory, then a variable is changed in the object's namespace, so that the code can stop itself. An optional destructor part can be used for further cleanup (remove listeners etc.)

It is using two properies <load> and <unload>. Example:

<?xml version="1.0"?>
<PropertyList>
       <path>helipad.ac</path>
       <nasal>
               <load>
                       loaded = 1;
                       print("Hello, I'm the helipad!");
                       var f = func {
                               if (!loaded) { return }
                               print("I'm still there!");
                               settimer(f, 5);
                       }
                       f();
               </load>
               <unload>
                       loaded = 0;
                       print("Bye, bye!")
               </unload>
       </nasal>
       <animation>
               <type>noshadow</type>
               <object-name>helipad</object-name>
       </animation>
</PropertyList>

Advice for testing: The object has to be present at sim startup. If you place an object with the UFO the xml-code gets executed, but not the NASAL code.