20,741
edits
Howto:Add new fgcommands to FlightGear: Difference between revisions
Jump to navigation
Jump to search
m
Howto:Add new fgcommands to FlightGear (view source)
Revision as of 12:53, 10 February 2012
, 10 February 2012→Background
m (→Background) |
m (→Background) |
||
| Line 4: | Line 4: | ||
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. | 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. | ||
So there is a certain marshaling/conversion overhead involved here. While this is certainly negligible for simple commands that are run rarely, this overhead may add up once a certain fgcommand gets called repeatedly at a high rate. In such cases it may be more efficient to let the command work with argument lists (vectors) rather than ust a single argument, so that multiple tasks can be completed by a single invocation. | So there is a certain marshaling/conversion overhead involved here. While this is certainly negligible for simple commands that are run rarely, this overhead may add up once a certain fgcommand gets called repeatedly at a high rate. In such cases it may be more efficient to let the command work with argument lists (vectors) rather than ust a single argument, so that multiple tasks can be completed by a single invocation. | ||