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Howto:Add new fgcommands to FlightGear: Difference between revisions
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Howto:Add new fgcommands to FlightGear (view source)
Revision as of 12:55, 10 February 2012
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So called "fgcommands" are FlightGear extension functions which can be invoked in a number of different ways, such as embedded in various XML files (in the form of "action" bindings), but also via Nasal scripts using the fgcommand() extension function. In addition, it is also possible to invoke fgcommands using the telnet/props interface, so that a simple form of "Remote Procedure Calling" can be implemented, i.e. triggering code via telnet to be run inside the FlightGear process. | So called "'''fgcommands'''" are FlightGear extension functions which can be invoked in a number of different ways, such as embedded in various XML files (in the form of "action" bindings), but also via [[Nasal]] scripts using the '''fgcommand'''() extension function. In addition, it is also possible to invoke '''fgcommands''' using the telnet/props interface, so that a simple form of "Remote Procedure Calling" can be implemented, i.e. triggering code via telnet to be run inside the FlightGear process. | ||
Compared to Nasal extension functions, the nice thing about "fgcommands" is that they are not just available to Nasal scripts, but that they can also be used by lots of other FlightGear systems directly without resorting to scripts and registering listeners, such as in the form of GUI bindings, mouse/keyboard handlers and so on. | Compared to [[Nasal]] extension functions, the nice thing about "'''fgcommands'''" is that they are not just available to Nasal scripts, but that they can also be used by lots of other FlightGear systems directly without resorting to scripts and registering listeners, such as in the form of GUI bindings, mouse/keyboard handlers and so on. | ||
Of course, there are some disadvantages too: fgcommands always need their arguments wrapped in a property tree structure. This is because they don't have any concept of Nasal and its internal data structures, as they need to work with just XML files and the property tree. | Of course, there are some disadvantages too: fgcommands always need their arguments wrapped in a property tree structure. This is because they don't have any concept of Nasal and its internal data structures, as they need to work with just XML files and the property tree. | ||