See:
http://wiki.flightgear.org/Nasal_libraryTo learn more about timers and how they work in Nasal, see $FG_SRC/Scripting/NasalSys.cxx
The settimer() API is mapped to the f_settimer() C function here:
http://sourceforge.net/p/flightgear/fli ... s.cxx#l781The C code for this extension function can be seen here:
http://sourceforge.net/p/flightgear/fli ... s.cxx#l471That's only 3 lines of code, which ends up calling the FGNasalSys::setTimer() API at:
http://sourceforge.net/p/flightgear/fli ... .cxx#l1265- Code: Select all
// settimer(func, dt, simtime) extension function. The first argument
// is a Nasal function to call, the second is a delta time (from now),
// in seconds. The third, if present, is a boolean value indicating
// that "real world" time (rather than simulator time) is to be used.
//
// Implementation note: the FGTimer objects don't live inside the
// garbage collector, so the Nasal handler functions have to be
// "saved" somehow lest they be inadvertently cleaned. In this case,
// they are inserted into a globals.__gcsave hash and removed on
// expiration.
void FGNasalSys::setTimer(naContext c, int argc, naRef* args)
{
// Extract the handler, delta, and simtime arguments:
naRef handler = argc > 0 ? args[0] : naNil();
if(!(naIsCode(handler) || naIsCCode(handler) || naIsFunc(handler))) {
naRuntimeError(c, "settimer() with invalid function argument");
return;
}
naRef delta = argc > 1 ? args[1] : naNil();
if(naIsNil(delta)) {
naRuntimeError(c, "settimer() with invalid time argument");
return;
}
bool simtime = (argc > 2 && naTrue(args[2])) ? false : true;
// Generate and register a C++ timer handler
NasalTimer* t = new NasalTimer;
t->handler = handler;
t->gcKey = gcSave(handler);
t->nasal = this;
globals->get_event_mgr()->addEvent("NasalTimer",
t, &NasalTimer::timerExpired,
delta.num, simtime);
}
What this will do is create a temporary NasalTimer object, for the class/struct refer to:
http://sourceforge.net/p/flightgear/fli ... s.hxx#l163It will then set up the NasalTimer object according to the arguments you passed to settimer() - and ultimately, it will invoke the event manager to register the timer object:
http://sourceforge.net/p/flightgear/fli ... .cxx#l1298That really is all you need to know in order to check if a Nasal callback gets re-added, or if it is already running, because the "handler" parameter can be checked (e.g. use SG_LOG() to print out the address of the pointer).
Most of this would be also applicable to the setlistener() API, with the difference being that calls will not be specific to any particular subsystem like "events", but can be triggered by arbitrary subsystems which end up writing/modifying a property with a registered Nasal callback/listener.
These two are the most likely suspects when it comes to leaking callbacks and having redundant callbacks registered to be executed unnecessarily.
Note that the event manager lives in SimGear, and one simple thing you can do is to log the number of active timers to the console and/or to the property tree (e.g. using a propertyObject) - you will almost certainly see those grow over time, probably even with identical callbacks:
http://api-docs.freeflightsim.org/simge ... ntMgr.htmlThe other thing that can be done is to use SGTimeStamp::now() to benchmark the execution time of different callbacks.
None of this would be specific to the 777 - it would benefit any/all aircraft and other Nasal code suffering from these coding errors
Even if you don't feel comfortable writing C++ code, all you need to know is how to use the SG_LOG() macro to dump the size of a the timer queue:
http://api-docs.freeflightsim.org/simge ... Queue.htmlIt's
_numEntries that's relevant here, which is private, but can be exposed by adding a corresponding method
FlightGear Forum
