| 15 | | Each entity has a hierarchical tree of ''properties'' as well as a number of ''event handlers'' implemented in !JavaScript. Entity types (such as different soldier types) are defined as XML "template" files in binaries/data/mods/official/entities. These XML templates can inherit from each other, so that, for example, all spearmen can inherit some properties from template_infantry_spearman.xml, but Celtic and Persian spearmen can be differentiated by modifying celt_infantry_spearman.xml and pers_infantry_spearman.xml. A property such as maximum health might be implemented in an XML file as <traits><health><max>100</max></health></traits> and will then be accessible through scripts and C++ code as traits.health.max. The XML files also define script functions that can handle various ''events'' for an entity. For example, an entity may choose to react when it's damaged by attacking the entity that damaged it. Most orders which require the entity to do some work are implemented as events. For example, if a unit has an attack with attack rate of 1 hit per 2 seconds, then as long as it is trying to attack a target, it will get a "handle generic order" event with action "attack" ever 2 seconds, and then a !JavaScript function will decide how much damage to inflict on the target and do so. The C++ code only does the "heavy-duty" work like pathfinding and collision detection, allowing most of the game logic to be handled in !JavaScript for a quick development cycle. One last thing to note about entities is that although they have many properties, only the properties that differ from those in the template, such as "current health", are maintained for each CEntity object. The rest are held by the template (CEntityTemplate). This means that it's possible to, for example, upgrade the attack of all current and future entities of some type by applying a change to their template. Entity properties and event handlers are described in detail at http://www.wildfiregames.com/users/code/wiki/index.php?title=XML.Entity. Scripting helper functions are implemented in the scripting module - Most notably, the CJSObject class, which makes it possible to expose C++ instance variables and methods in an object to !JavaScript fields and functions. |
| | 15 | Each entity has a hierarchical tree of ''properties'' as well as a number of ''event handlers'' implemented in !JavaScript. Entity types (such as different soldier types) are defined as XML "template" files in binaries/data/mods/official/entities. These XML templates can inherit from each other, so that, for example, all spearmen can inherit some properties from template_infantry_spearman.xml, but Celtic and Persian spearmen can be differentiated by modifying celt_infantry_spearman.xml and pers_infantry_spearman.xml. A property such as maximum health might be implemented in an XML file as <traits><health><max>100</max></health></traits> and will then be accessible through scripts and C++ code as traits.health.max. The XML files also define script functions that can handle various ''events'' for an entity. For example, an entity may choose to react when it's damaged by attacking the entity that damaged it. Most orders which require the entity to do some work are implemented as events. For example, if a unit has an attack with attack rate of 1 hit per 2 seconds, then as long as it is trying to attack a target, it will get a "handle generic order" event with action "attack" ever 2 seconds, and then a !JavaScript function will decide how much damage to inflict on the target and do so. The C++ code only does the "heavy-duty" work like pathfinding and collision detection, allowing most of the game logic to be handled in !JavaScript for a quick development cycle. One last thing to note about entities is that although they have many properties, only the properties that differ from those in the template, such as "current health", are maintained for each CEntity object. The rest are held by the template (CEntityTemplate). This means that it's possible to, for example, upgrade the attack of all current and future entities of some type by applying a change to their template. Entity properties and event handlers are described in detail at [wiki:XML.Entity XML.Entity]. Scripting helper functions are implemented in the scripting module - Most notably, the CJSObject class, which makes it possible to expose C++ instance variables and methods in an object to !JavaScript fields and functions. |
