X-Git-Url: https://git.mxchange.org/?a=blobdiff_plain;f=src%2FScripting%2FNasalSys.cxx;h=991147e790c5619d3b4e0ad14e24f86fe1f47612;hb=50e19ee23970db9bf7314d74f0ed223d8bf702c0;hp=80adc19eaa63dac153fbd020f9ad6260d0096d72;hpb=79e48829da50e0103e81684896b8287bfe23cc96;p=flightgear.git

diff --git a/src/Scripting/NasalSys.cxx b/src/Scripting/NasalSys.cxx
index 80adc19ea..991147e79 100644
--- a/src/Scripting/NasalSys.cxx
+++ b/src/Scripting/NasalSys.cxx
@@ -1,19 +1,38 @@
+
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
+#ifdef HAVE_SYS_TIME_H
+#  include <sys/time.h>  // gettimeofday
+#endif
+
 #include <string.h>
 #include <stdio.h>
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <fstream>
 
 #include <plib/ul.h>
 
 #include <simgear/nasal/nasal.h>
 #include <simgear/props/props.hxx>
+#include <simgear/math/sg_random.h>
 #include <simgear/misc/sg_path.hxx>
+#include <simgear/misc/interpolator.hxx>
+#include <simgear/scene/material/mat.hxx>
 #include <simgear/structure/commands.hxx>
+#include <simgear/math/sg_geodesy.hxx>
 
 #include <Main/globals.hxx>
+#include <Main/fg_props.hxx>
+#include <Scenery/scenery.hxx>
 
 #include "NasalSys.hxx"
 
+static FGNasalSys* nasalSys = 0;
+
+
 // Read and return file contents in a single buffer.  Note use of
 // stat() to get the file size.  This is a win32 function, believe it
 // or not. :) Note the REALLY IMPORTANT use of the "b" flag to fopen.
@@ -44,20 +63,43 @@ static char* readfile(const char* file, int* lenOut)
 
 FGNasalSys::FGNasalSys()
 {
+    nasalSys = this;
     _context = 0;
     _globals = naNil();
-    _timerHash = naNil();
-    _nextTimerHashKey = 0; // Any value will do
+    _gcHash = naNil();
+    _nextGCKey = 0; // Any value will do
+    _callCount = 0;
+    _purgeListeners = false;
+}
+
+// Does a naCall() in a new context.  Wrapped here to make lock
+// tracking easier.  Extension functions are called with the lock, but
+// we have to release it before making a new naCall().  So rather than
+// drop the lock in every extension function that might call back into
+// Nasal, we keep a stack depth counter here and only unlock/lock
+// around the naCall if it isn't the first one.
+naRef FGNasalSys::call(naRef code, naRef locals)
+{
+    naContext ctx = naNewContext();
+    if(_callCount) naModUnlock();
+    _callCount++;
+    naRef result = naCall(ctx, code, 0, 0, naNil(), locals);
+    if(naGetError(ctx))
+        logError(ctx);
+    _callCount--;
+    if(_callCount) naModLock();
+    naFreeContext(ctx);
+    return result;
 }
 
 FGNasalSys::~FGNasalSys()
 {
-    // Nasal doesn't have a "destroy context" API yet. :(
-    // Not a problem for a global subsystem that will never be
-    // destroyed.  And the context is actually a global, so no memory
-    // is technically leaked (although the GC pool memory obviously
-    // won't be freed).
-    _context = 0;
+    nasalSys = 0;
+    map<int, FGNasalListener *>::iterator it, end = _listener.end();
+    for(it = _listener.begin(); it != end; ++it)
+        delete it->second;
+
+    naFreeContext(_context);
     _globals = naNil();
 }
 
@@ -67,12 +109,30 @@ bool FGNasalSys::parseAndRun(const char* sourceCode)
                        strlen(sourceCode));
     if(naIsNil(code))
         return false;
+    call(code, naNil());
+    return true;
+}
 
-    naCall(_context, code, naNil(), naNil(), naNil());
+FGNasalScript* FGNasalSys::parseScript(const char* src, const char* name)
+{
+    FGNasalScript* script = new FGNasalScript();
+    script->_gcKey = -1; // important, if we delete it on a parse
+    script->_nas = this; // error, don't clobber a real handle!
+
+    char buf[256];
+    if(!name) {
+        sprintf(buf, "FGNasalScript@%p", (void *)script);
+        name = buf;
+    }
 
-    if(!naGetError(_context)) return true;
-    logError();
-    return false;
+    script->_code = parse(name, src, strlen(src));
+    if(naIsNil(script->_code)) {
+        delete script;
+        return 0;
+    }
+
+    script->_gcKey = gcSave(script->_code);
+    return script;
 }
 
 // Utility.  Sets a named key in a hash by C string, rather than nasal
@@ -91,14 +151,19 @@ void FGNasalSys::hashset(naRef hash, const char* key, naRef val)
 // is the utility function that walks the property tree.
 // Future enhancement: support integer arguments to specify array
 // elements.
-static SGPropertyNode* findnode(naContext c, naRef vec, int len)
+static SGPropertyNode* findnode(naContext c, naRef* vec, int len)
 {
     SGPropertyNode* p = globals->get_props();
-    for(int i=0; i<len; i++) {
-        naRef a = naVec_get(vec, i);
-        if(!naIsString(a)) return 0;
-        p = p->getNode(naStr_data(a));
-        if(p == 0) return 0;
+    try {
+        for(int i=0; i<len; i++) {
+            naRef a = vec[i];
+            if(!naIsString(a)) return 0;
+            p = p->getNode(naStr_data(a));
+            if(p == 0) return 0;
+        }
+    } catch (const string& err) {
+        naRuntimeError(c, (char *)err.c_str());
+        return 0;
     }
     return p;
 }
@@ -106,9 +171,9 @@ static SGPropertyNode* findnode(naContext c, naRef vec, int len)
 // getprop() extension function.  Concatenates its string arguments as
 // property names and returns the value of the specified property.  Or
 // nil if it doesn't exist.
-static naRef f_getprop(naContext c, naRef args)
+static naRef f_getprop(naContext c, naRef me, int argc, naRef* args)
 {
-    const SGPropertyNode* p = findnode(c, args, naVec_size(args));
+    const SGPropertyNode* p = findnode(c, args, argc);
     if(!p) return naNil();
 
     switch(p->getType()) {
@@ -118,12 +183,14 @@ static naRef f_getprop(naContext c, naRef args)
         return naNum(p->getDoubleValue());
 
     case SGPropertyNode::STRING:
+    case SGPropertyNode::UNSPECIFIED:
         {
             naRef nastr = naNewString(c);
             const char* val = p->getStringValue();
             naStr_fromdata(nastr, (char*)val, strlen(val));
             return nastr;
         }
+    case SGPropertyNode::ALIAS: // <--- FIXME, recurse?
     default:
         return naNil();
     }
@@ -132,16 +199,15 @@ static naRef f_getprop(naContext c, naRef args)
 // setprop() extension function.  Concatenates its string arguments as
 // property names and sets the value of the specified property to the
 // final argument.
-static naRef f_setprop(naContext c, naRef args)
+static naRef f_setprop(naContext c, naRef me, int argc, naRef* args)
 {
 #define BUFLEN 1024
-    int argc = naVec_size(args);
     char buf[BUFLEN + 1];
     buf[BUFLEN] = 0;
     char* p = buf;
     int buflen = BUFLEN;
     for(int i=0; i<argc-1; i++) {
-        naRef s = naStringValue(c, naVec_get(args, i));
+        naRef s = naStringValue(c, args[i]);
         if(naIsNil(s)) return naNil();
         strncpy(p, naStr_data(s), buflen);
         p += naStr_len(s);
@@ -153,9 +219,18 @@ static naRef f_setprop(naContext c, naRef args)
     }
 
     SGPropertyNode* props = globals->get_props();
-    naRef val = naVec_get(args, argc-1);
-    if(naIsString(val)) props->setStringValue(buf, naStr_data(val));
-    else                props->setDoubleValue(buf, naNumValue(val).num);
+    naRef val = args[argc-1];
+    try {
+        if(naIsString(val)) props->setStringValue(buf, naStr_data(val));
+        else {
+            naRef n = naNumValue(val);
+            if(naIsNil(n))
+                naRuntimeError(c, "setprop() value is not string or number");
+            props->setDoubleValue(buf, n.num);
+        }
+    } catch (const string& err) {
+        naRuntimeError(c, (char *)err.c_str());
+    }
     return naNil();
 #undef BUFLEN
 }
@@ -163,56 +238,247 @@ static naRef f_setprop(naContext c, naRef args)
 // print() extension function.  Concatenates and prints its arguments
 // to the FlightGear log.  Uses the highest log level (SG_ALERT), to
 // make sure it appears.  Is there better way to do this?
-static naRef f_print(naContext c, naRef args)
+static naRef f_print(naContext c, naRef me, int argc, naRef* args)
 {
-#define BUFLEN 1024
-    char buf[BUFLEN + 1];
-    buf[BUFLEN] = 0; // extra nul to handle strncpy brain damage
-    char* p = buf;
-    int buflen = BUFLEN;
-    int n = naVec_size(args);
+    string buf;
+    int n = argc;
     for(int i=0; i<n; i++) {
-        naRef s = naStringValue(c, naVec_get(args, i));
+        naRef s = naStringValue(c, args[i]);
         if(naIsNil(s)) continue;
-        strncpy(p, naStr_data(s), buflen);
-        p += naStr_len(s);
-        buflen = BUFLEN - (p - buf);
-        if(buflen <= 0) break;
+        buf += naStr_data(s);
     }
     SG_LOG(SG_GENERAL, SG_ALERT, buf);
-    return naNil();
-#undef BUFLEN
+    return naNum(buf.length());
 }
 
 // fgcommand() extension function.  Executes a named command via the
 // FlightGear command manager.  Takes a single property node name as
 // an argument.
-static naRef f_fgcommand(naContext c, naRef args)
+static naRef f_fgcommand(naContext c, naRef me, int argc, naRef* args)
 {
-    naRef cmd = naVec_get(args, 0);
-    naRef props = naVec_get(args, 1);
-    if(!naIsString(cmd) || !naIsGhost(props)) return naNil();
-    SGPropertyNode_ptr* node = (SGPropertyNode_ptr*)naGhost_ptr(props);
-    globals->get_commands()->execute(naStr_data(cmd), *node);
-    return naNil();
-
+    naRef cmd = argc > 0 ? args[0] : naNil();
+    naRef props = argc > 1 ? args[1] : naNil();
+    if(!naIsString(cmd) || (!naIsNil(props) && !naIsGhost(props)))
+        naRuntimeError(c, "bad arguments to fgcommand()");
+    SGPropertyNode_ptr tmp, *node;
+    if(!naIsNil(props))
+        node = (SGPropertyNode_ptr*)naGhost_ptr(props);
+    else {
+        tmp = new SGPropertyNode();
+        node = &tmp;
+    }
+    return naNum(globals->get_commands()->execute(naStr_data(cmd), *node));
 }
 
 // settimer(func, dt, simtime) extension function.  Falls through to
 // FGNasalSys::setTimer().  See there for docs.
-static naRef f_settimer(naContext c, naRef args)
+static naRef f_settimer(naContext c, naRef me, int argc, naRef* args)
 {
-    FGNasalSys* nasal = (FGNasalSys*)globals->get_subsystem("nasal");
-    nasal->setTimer(args);
+    nasalSys->setTimer(c, argc, args);
     return naNil();
 }
 
+// setlistener(func, property, bool) extension function.  Falls through to
+// FGNasalSys::setListener().  See there for docs.
+static naRef f_setlistener(naContext c, naRef me, int argc, naRef* args)
+{
+    return nasalSys->setListener(c, argc, args);
+}
+
+// removelistener(int) extension function. Falls through to
+// FGNasalSys::removeListener(). See there for docs.
+static naRef f_removelistener(naContext c, naRef me, int argc, naRef* args)
+{
+    return nasalSys->removeListener(c, argc, args);
+}
+
 // Returns a ghost handle to the argument to the currently executing
 // command
-static naRef f_cmdarg(naContext c, naRef args)
+static naRef f_cmdarg(naContext c, naRef me, int argc, naRef* args)
+{
+    return nasalSys->cmdArgGhost();
+}
+
+// Sets up a property interpolation.  The first argument is either a
+// ghost (SGPropertyNode_ptr*) or a string (global property path) to
+// interpolate.  The second argument is a vector of pairs of
+// value/delta numbers.
+static naRef f_interpolate(naContext c, naRef me, int argc, naRef* args)
+{
+    SGPropertyNode* node;
+    naRef prop = argc > 0 ? args[0] : naNil();
+    if(naIsString(prop)) node = fgGetNode(naStr_data(prop), true);
+    else if(naIsGhost(prop)) node = *(SGPropertyNode_ptr*)naGhost_ptr(prop);
+    else return naNil();
+
+    naRef curve = argc > 1 ? args[1] : naNil();
+    if(!naIsVector(curve)) return naNil();
+    int nPoints = naVec_size(curve) / 2;
+    double* values = new double[nPoints];
+    double* deltas = new double[nPoints];
+    for(int i=0; i<nPoints; i++) {
+        values[i] = naNumValue(naVec_get(curve, 2*i)).num;
+        deltas[i] = naNumValue(naVec_get(curve, 2*i+1)).num;
+    }
+
+    ((SGInterpolator*)globals->get_subsystem_mgr()
+        ->get_group(SGSubsystemMgr::INIT)->get_subsystem("interpolator"))
+        ->interpolate(node, nPoints, values, deltas);
+
+    return naNil();
+}
+
+// This is a better RNG than the one in the default Nasal distribution
+// (which is based on the C library rand() implementation). It will
+// override.
+static naRef f_rand(naContext c, naRef me, int argc, naRef* args)
 {
-    FGNasalSys* nasal = (FGNasalSys*)globals->get_subsystem("nasal");
-    return nasal->cmdArgGhost();
+    return naNum(sg_random());
+}
+
+static naRef f_srand(naContext c, naRef me, int argc, naRef* args)
+{
+    sg_srandom_time();
+    return naNum(0);
+}
+
+// Return an array listing of all files in a directory
+static naRef f_directory(naContext c, naRef me, int argc, naRef* args)
+{
+    if(argc != 1 || !naIsString(args[0]))
+        naRuntimeError(c, "bad arguments to directory()");
+    naRef ldir = args[0];
+    ulDir* dir = ulOpenDir(naStr_data(args[0]));
+    if(!dir) return naNil();
+    naRef result = naNewVector(c);
+    ulDirEnt* dent;
+    while((dent = ulReadDir(dir)))
+        naVec_append(result, naStr_fromdata(naNewString(c), dent->d_name,
+                                            strlen(dent->d_name)));
+    ulCloseDir(dir);
+    return result;
+}
+
+// Parse XML file.
+//     parsexml(<path> [, <start-tag> [, <end-tag> [, <data> [, <pi>]]]]);
+//
+// <path>      ... absolute path of an XML file
+// <start-tag> ... callback function with two args: tag name, attribute hash
+// <end-tag>   ... callback function with one arg:  tag name
+// <data>      ... callback function with one arg:  data
+// <pi>        ... callback function with two args: target, data
+//                 (pi = "processing instruction")
+// All four callback functions are optional and default to nil.
+// The function returns nil on error, and the file name otherwise.
+static naRef f_parsexml(naContext c, naRef me, int argc, naRef* args)
+{
+    if(argc < 1 || !naIsString(args[0]))
+        naRuntimeError(c, "parsexml(): path argument missing or not a string");
+    if(argc > 5) argc = 5;
+    for(int i=1; i<argc; i++)
+        if(!(naIsNil(args[i]) || naIsFunc(args[i])))
+            naRuntimeError(c, "parsexml(): callback argument not a function");
+
+    const char* file = naStr_data(args[0]);
+    std::ifstream input(file);
+    NasalXMLVisitor visitor(c, argc, args);
+    try {
+        readXML(input, visitor);
+    } catch (const sg_exception& e) {
+        string msg = string("parsexml(): file '") + file + "' "
+                     + e.getFormattedMessage();
+        naRuntimeError(c, msg.c_str());
+        return naNil();
+    }
+    return args[0];
+}
+
+// Return UNIX epoch time in seconds.
+static naRef f_systime(naContext c, naRef me, int argc, naRef* args)
+{
+#ifdef WIN32
+    FILETIME ft;
+    GetSystemTimeAsFileTime(&ft);
+    double t = (4294967296.0 * ft.dwHighDateTime + ft.dwLowDateTime);
+    // Converts from 100ns units in 1601 epoch to unix epoch in sec
+    return naNum((t * 1e-7) - 11644473600.0);
+#else
+    time_t t;
+    struct timeval td;
+    do { t = time(0); gettimeofday(&td, 0); } while(t != time(0));
+    return naNum(t + 1e-6 * td.tv_usec);
+#endif
+
+}
+
+// Convert a cartesian point to a geodetic lat/lon/altitude.
+static naRef f_carttogeod(naContext c, naRef me, int argc, naRef* args)
+{
+    double lat, lon, alt, xyz[3];
+    if(argc != 3) naRuntimeError(c, "carttogeod() expects 3 arguments");
+    for(int i=0; i<3; i++)
+        xyz[i] = naNumValue(args[i]).num;
+    sgCartToGeod(xyz, &lat, &lon, &alt);
+    lat *= SG_RADIANS_TO_DEGREES;
+    lon *= SG_RADIANS_TO_DEGREES;
+    naRef vec = naNewVector(c);
+    naVec_append(vec, naNum(lat));
+    naVec_append(vec, naNum(lon));
+    naVec_append(vec, naNum(alt));
+    return vec;
+}
+
+// Convert a geodetic lat/lon/altitude to a cartesian point.
+static naRef f_geodtocart(naContext c, naRef me, int argc, naRef* args)
+{
+    if(argc != 3) naRuntimeError(c, "geodtocart() expects 3 arguments");
+    double lat = naNumValue(args[0]).num * SG_DEGREES_TO_RADIANS;
+    double lon = naNumValue(args[1]).num * SG_DEGREES_TO_RADIANS;
+    double alt = naNumValue(args[2]).num;
+    double xyz[3];
+    sgGeodToCart(lat, lon, alt, xyz);
+    naRef vec = naNewVector(c);
+    naVec_append(vec, naNum(xyz[0]));
+    naVec_append(vec, naNum(xyz[1]));
+    naVec_append(vec, naNum(xyz[2]));
+    return vec;
+}
+
+// For given geodetic point return array with elevation, and a material data
+// hash, or nil if there's no information available (tile not loaded). If
+// information about the material isn't available, then nil is returned instead
+// of the hash.
+static naRef f_geodinfo(naContext c, naRef me, int argc, naRef* args)
+{
+#define HASHSET(s,l,n) naHash_set(matdata, naStr_fromdata(naNewString(c),s,l),n)
+    if(argc != 2) naRuntimeError(c, "geodinfo() expects 2 arguments: lat, lon");
+    double lat = naNumValue(args[0]).num;
+    double lon = naNumValue(args[1]).num;
+    double elev;
+    const SGMaterial *mat;
+    if(!globals->get_scenery()->get_elevation_m(lat, lon, 10000.0, elev, &mat))
+        return naNil();
+    naRef vec = naNewVector(c);
+    naVec_append(vec, naNum(elev));
+    naRef matdata = naNil();
+    if(mat) {
+        matdata = naNewHash(c);
+        naRef names = naNewVector(c);
+        const vector<string> n = mat->get_names();
+        for(unsigned int i=0; i<n.size(); i++)
+            naVec_append(names, naStr_fromdata(naNewString(c),
+                    const_cast<char*>(n[i].c_str()), n[i].size()));
+        HASHSET("names", 5, names);
+        HASHSET("solid", 5, naNum(mat->get_solid()));
+        HASHSET("friction_factor", 15, naNum(mat->get_friction_factor()));
+        HASHSET("rolling_friction", 16, naNum(mat->get_rolling_friction()));
+        HASHSET("load_resistance", 15, naNum(mat->get_load_resistance()));
+        HASHSET("bumpiness", 9, naNum(mat->get_bumpiness()));
+        HASHSET("light_coverage", 14, naNum(mat->get_light_coverage()));
+    }
+    naVec_append(vec, matdata);
+    return vec;
+#undef HASHSET
 }
 
 // Table of extension functions.  Terminate with zeros.
@@ -222,7 +488,18 @@ static struct { char* name; naCFunction func; } funcs[] = {
     { "print",     f_print },
     { "_fgcommand", f_fgcommand },
     { "settimer",  f_settimer },
+    { "_setlistener", f_setlistener },
+    { "removelistener", f_removelistener },
     { "_cmdarg",  f_cmdarg },
+    { "_interpolate",  f_interpolate },
+    { "rand",  f_rand },
+    { "srand",  f_srand },
+    { "directory", f_directory },
+    { "parsexml", f_parsexml },
+    { "systime", f_systime },
+    { "carttogeod", f_carttogeod },
+    { "geodtocart", f_geodtocart },
+    { "geodinfo", f_geodinfo },
     { 0, 0 }
 };
 
@@ -241,12 +518,15 @@ void FGNasalSys::init()
     // sub-reference under the name "globals".  This gives client-code
     // write access to the namespace if someone wants to do something
     // fancy.
-    _globals = naStdLib(_context);
+    _globals = naInit_std(_context);
     naSave(_context, _globals);
     hashset(_globals, "globals", _globals);
 
-    // Add in the math library under "math"
-    hashset(_globals, "math", naMathLib(_context));
+    hashset(_globals, "math", naInit_math(_context));
+    hashset(_globals, "bits", naInit_bits(_context));
+    hashset(_globals, "io", naInit_io(_context));
+    hashset(_globals, "thread", naInit_thread(_context));
+    hashset(_globals, "utf8", naInit_utf8(_context));
 
     // Add our custom extension functions:
     for(i=0; funcs[i].name; i++)
@@ -256,10 +536,11 @@ void FGNasalSys::init()
     // And our SGPropertyNode wrapper
     hashset(_globals, "props", genPropsModule());
 
-    // Make a "__timers" hash to hold the settimer() handlers (to
-    // protect them from begin garbage-collected).
-    _timerHash = naNewHash(_context);
-    hashset(_globals, "__timers", _timerHash);
+    // Make a "__gcsave" hash to hold the naRef objects which get
+    // passed to handles outside the interpreter (to protect them from
+    // begin garbage-collected).
+    _gcHash = naNewHash(_context);
+    hashset(_globals, "__gcsave", _gcHash);
 
     // Now load the various source files in the Nasal directory
     SGPath p(globals->get_fg_root());
@@ -271,13 +552,37 @@ void FGNasalSys::init()
         fullpath.append(dent->d_name);
         SGPath file(dent->d_name);
         if(file.extension() != "nas") continue;
-        readScriptFile(fullpath, file.base().c_str());
+        loadModule(fullpath, file.base().c_str());
     }
+    ulCloseDir(dir);
+
+    // set signal and remove node to avoid restoring at reinit
+    const char *s = "nasal-dir-initialized";
+    SGPropertyNode *signal = fgGetNode("/sim/signals", true);
+    signal->setBoolValue(s, true);
+    signal->removeChildren(s);
 
     // Pull scripts out of the property tree, too
     loadPropertyScripts();
 }
 
+void FGNasalSys::update(double)
+{
+    if(_purgeListeners) {
+        _purgeListeners = false;
+        map<int, FGNasalListener *>::iterator it;
+        for(it = _listener.begin(); it != _listener.end();) {
+            FGNasalListener *nl = it->second;
+            if(nl->_dead) {
+                _listener.erase(it++);
+                delete nl;
+            } else {
+                ++it;
+            }
+        }
+    }
+}
+
 // Loads the scripts found under /nasal in the global tree
 void FGNasalSys::loadPropertyScripts()
 {
@@ -291,20 +596,37 @@ void FGNasalSys::loadPropertyScripts()
         if(n->hasChild("module"))
             module = n->getStringValue("module");
 
+        // allow multiple files to be specified within in a single
+        // Nasal module tag
+        int j = 0;
+        SGPropertyNode *fn;
+        bool file_specified = false;
+        while ( (fn = n->getChild("file", j)) != NULL ) {
+            file_specified = true;
+            const char* file = fn->getStringValue();
+            SGPath p(globals->get_fg_root());
+            p.append(file);
+            loadModule(p, module);
+            j++;
+        }
+
+        // Old code which only allowed a single file to be specified per module
+        /*
         const char* file = n->getStringValue("file");
         if(!n->hasChild("file")) file = 0; // Hrm...
         if(file) {
             SGPath p(globals->get_fg_root());
             p.append(file);
-            readScriptFile(p, module);
+            loadModule(p, module);
         }
-        
+        */
+
         const char* src = n->getStringValue("script");
         if(!n->hasChild("script")) src = 0; // Hrm...
         if(src)
-            initModule(module, n->getPath(), src, strlen(src));
+            createModule(module, n->getPath(), src, strlen(src));
 
-        if(!file && !src)
+        if(!file_specified && !src)
             SG_LOG(SG_NASAL, SG_ALERT, "Nasal error: " <<
                    "no <file> or <script> defined in " <<
                    "/nasal/" << module);
@@ -312,23 +634,23 @@ void FGNasalSys::loadPropertyScripts()
 }
 
 // Logs a runtime error, with stack trace, to the FlightGear log stream
-void FGNasalSys::logError()
+void FGNasalSys::logError(naContext context)
 {
     SG_LOG(SG_NASAL, SG_ALERT,
-           "Nasal runtime error: " << naGetError(_context));
+           "Nasal runtime error: " << naGetError(context));
     SG_LOG(SG_NASAL, SG_ALERT,
-           "  at " << naStr_data(naGetSourceFile(_context, 0)) <<
-           ", line " << naGetLine(_context, 0));
-    for(int i=1; i<naStackDepth(_context); i++)
+           "  at " << naStr_data(naGetSourceFile(context, 0)) <<
+           ", line " << naGetLine(context, 0));
+    for(int i=1; i<naStackDepth(context); i++)
         SG_LOG(SG_NASAL, SG_ALERT,
-               "  called from: " << naStr_data(naGetSourceFile(_context, i)) <<
-               ", line " << naGetLine(_context, i));
+               "  called from: " << naStr_data(naGetSourceFile(context, i)) <<
+               ", line " << naGetLine(context, i));
 }
 
 // Reads a script file, executes it, and places the resulting
 // namespace into the global namespace under the specified module
 // name.
-void FGNasalSys::readScriptFile(SGPath file, const char* module)
+void FGNasalSys::loadModule(SGPath file, const char* module)
 {
     int len = 0;
     char* buf = readfile(file.c_str(), &len);
@@ -339,17 +661,17 @@ void FGNasalSys::readScriptFile(SGPath file, const char* module)
         return;
     }
 
-    initModule(module, file.c_str(), buf, len);
+    createModule(module, file.c_str(), buf, len);
     delete[] buf;
 }
 
 // Parse and run.  Save the local variables namespace, as it will
-// become a sub-object of globals.
-void FGNasalSys::initModule(const char* moduleName, const char* fileName,
-                            const char* src, int len)
+// become a sub-object of globals.  The optional "arg" argument can be
+// used to pass an associated property node to the module, which can then
+// be accessed via cmdarg().  (This is, for example, used by XML dialogs.)
+void FGNasalSys::createModule(const char* moduleName, const char* fileName,
+                              const char* src, int len, const SGPropertyNode* arg)
 {
-    if(len == 0) len = strlen(src);
-
     naRef code = parse(fileName, src, len);
     if(naIsNil(code))
         return;
@@ -363,14 +685,19 @@ void FGNasalSys::initModule(const char* moduleName, const char* fileName,
     if(!naHash_get(_globals, modname, &locals))
         locals = naNewHash(_context);
 
-    naCall(_context, code, naNil(), naNil(), locals);
-    if(naGetError(_context)) {
-        logError();
-        return;
-    }
+    _cmdArg = (SGPropertyNode*)arg;
+
+    call(code, locals);
     hashset(_globals, moduleName, locals);
 }
 
+void FGNasalSys::deleteModule(const char* moduleName)
+{
+    naRef modname = naNewString(_context);
+    naStr_fromdata(modname, (char*)moduleName, strlen(moduleName));
+    naHash_delete(_globals, modname);
+}
+
 naRef FGNasalSys::parse(const char* filename, const char* buf, int len)
 {
     int errLine = -1;
@@ -390,68 +717,87 @@ naRef FGNasalSys::parse(const char* filename, const char* buf, int len)
 
 bool FGNasalSys::handleCommand(const SGPropertyNode* arg)
 {
-    // Parse the Nasal source.  I'd love to use the property name of
-    // the argument, but it's actually a *clone* of the original
-    // location in the property tree.  arg->getPath() returns an empty
-    // string.
     const char* nasal = arg->getStringValue("script");
-    naRef code = parse("<command>", nasal, strlen(nasal));
+    const char* moduleName = arg->getStringValue("module");
+    naRef code = parse(arg->getPath(true), nasal, strlen(nasal));
     if(naIsNil(code)) return false;
-    
-    // Cache the command argument for inspection via cmdarg().  For
+
+    // Commands can be run "in" a module.  Make sure that module
+    // exists, and set it up as the local variables hash for the
+    // command.
+    naRef locals = naNil();
+    if(moduleName[0]) {
+        naRef modname = naNewString(_context);
+        naStr_fromdata(modname, (char*)moduleName, strlen(moduleName));
+        if(!naHash_get(_globals, modname, &locals)) {
+            locals = naNewHash(_context);
+            naHash_set(_globals, modname, locals);
+        }
+    }
+
+    // Cache this command's argument for inspection via cmdarg().  For
     // performance reasons, we won't bother with it if the invoked
     // code doesn't need it.
     _cmdArg = (SGPropertyNode*)arg;
 
-    // Call it!
-    naRef result = naCall(_context, code, naNil(), naNil(), naNil());
-    if(!naGetError(_context)) return true;
-    logError();
-    return false;
+    call(code, locals);
+    return true;
 }
 
 // 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 "simulator" time (rather than real time) is to be used.
+// 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._timers hash and removed on
+// they are inserted into a globals.__gcsave hash and removed on
 // expiration.
-void FGNasalSys::setTimer(naRef args)
+void FGNasalSys::setTimer(naContext c, int argc, naRef* args)
 {
     // Extract the handler, delta, and simtime arguments:
-    naRef handler = naVec_get(args, 0);
-    if(!(naIsCode(handler) || naIsCCode(handler) || naIsFunc(handler)))
+    naRef handler = argc > 0 ? args[0] : naNil();
+    if(!(naIsCode(handler) || naIsCCode(handler) || naIsFunc(handler))) {
+        naRuntimeError(c, "settimer() with invalid function argument");
         return;
+    }
 
-    naRef delta = naNumValue(naVec_get(args, 1));
-    if(naIsNil(delta)) return;
-    
-    bool simtime = naTrue(naVec_get(args, 2)) ? true : false;
+    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->hashKey = _nextTimerHashKey++;
+    t->gcKey = gcSave(handler);
     t->nasal = this;
 
     globals->get_event_mgr()->addEvent("NasalTimer",
                                        t, &NasalTimer::timerExpired,
                                        delta.num, simtime);
+}
 
+void FGNasalSys::handleTimer(NasalTimer* t)
+{
+    call(t->handler, naNil());
+    gcRelease(t->gcKey);
+}
 
-    // Save the handler in the globals.__timers hash to prevent
-    // garbage collection.
-    naHash_set(_timerHash, naNum(t->hashKey), handler);
+int FGNasalSys::gcSave(naRef r)
+{
+    int key = _nextGCKey++;
+    naHash_set(_gcHash, naNum(key), r);
+    return key;
 }
 
-void FGNasalSys::handleTimer(NasalTimer* t)
+void FGNasalSys::gcRelease(int key)
 {
-    naCall(_context, t->handler, naNil(), naNil(), naNil());
-    naHash_delete(_timerHash, naNum(t->hashKey));
+    naHash_delete(_gcHash, naNum(key));
 }
 
 void FGNasalSys::NasalTimer::timerExpired()
@@ -459,3 +805,202 @@ void FGNasalSys::NasalTimer::timerExpired()
     nasal->handleTimer(this);
     delete this;
 }
+
+int FGNasalSys::_listenerId = 0;
+
+// setlistener(property, func, bool) extension function.  The first argument
+// is either a ghost (SGPropertyNode_ptr*) or a string (global property
+// path), the second is a Nasal function, the optional third one a bool.
+// If the bool is true, then the listener is executed initially. The
+// setlistener() function returns a unique id number, that can be used
+// as argument to the removelistener() function.
+naRef FGNasalSys::setListener(naContext c, int argc, naRef* args)
+{
+    SGPropertyNode_ptr node;
+    naRef prop = argc > 0 ? args[0] : naNil();
+    if(naIsString(prop)) node = fgGetNode(naStr_data(prop), true);
+    else if(naIsGhost(prop)) node = *(SGPropertyNode_ptr*)naGhost_ptr(prop);
+    else {
+        naRuntimeError(c, "setlistener() with invalid property argument");
+        return naNil();
+    }
+
+    if(node->isTied())
+        SG_LOG(SG_NASAL, SG_DEBUG, "Attaching listener to tied property " <<
+                node->getPath());
+
+    naRef handler = argc > 1 ? args[1] : naNil();
+    if(!(naIsCode(handler) || naIsCCode(handler) || naIsFunc(handler))) {
+        naRuntimeError(c, "setlistener() with invalid function argument");
+        return naNil();
+    }
+
+    bool initial = argc > 2 && naTrue(args[2]);
+
+    FGNasalListener *nl = new FGNasalListener(node, handler, this,
+            gcSave(handler), _listenerId);
+    node->addChangeListener(nl, initial);
+
+    _listener[_listenerId] = nl;
+    return naNum(_listenerId++);
+}
+
+// removelistener(int) extension function. The argument is the id of
+// a listener as returned by the setlistener() function.
+naRef FGNasalSys::removeListener(naContext c, int argc, naRef* args)
+{
+    naRef id = argc > 0 ? args[0] : naNil();
+    map<int, FGNasalListener *>::iterator it = _listener.find(int(id.num));
+
+    if(!naIsNum(id) || it == _listener.end() || it->second->_dead) {
+        naRuntimeError(c, "removelistener() with invalid listener id");
+        return naNil();
+    }
+
+    FGNasalListener *nl = it->second;
+    if(nl->_active) {
+        nl->_dead = true;
+        _purgeListeners = true;
+        return naNum(-1);
+    }
+
+    _listener.erase(it);
+    delete nl;
+    return naNum(_listener.size());
+}
+
+
+
+// FGNasalListener class.
+
+FGNasalListener::FGNasalListener(SGPropertyNode_ptr node, naRef handler,
+                                 FGNasalSys* nasal, int key, int id) :
+    _node(node),
+    _handler(handler),
+    _gcKey(key),
+    _id(id),
+    _nas(nasal),
+    _active(0),
+    _dead(false)
+{
+}
+
+FGNasalListener::~FGNasalListener()
+{
+    _node->removeChangeListener(this);
+    _nas->gcRelease(_gcKey);
+}
+
+void FGNasalListener::valueChanged(SGPropertyNode* node)
+{
+    // drop recursive listener calls
+    if(_active || _dead)
+        return;
+
+    SG_LOG(SG_NASAL, SG_DEBUG, "trigger listener #" << _id);
+    _active++;
+    _nas->_cmdArg = node;
+    _nas->call(_handler, naNil());
+    _active--;
+}
+
+
+
+
+// FGNasalModelData class.  If sgLoad3DModel() is called with a pointer to
+// such a class, then it lets modelLoaded() run the <load> script, and the
+// destructor the <unload> script. The latter happens when the model branch
+// is removed from the scene graph.
+
+void FGNasalModelData::modelLoaded(const string& path, SGPropertyNode *prop,
+                                   osg::Node *)
+{
+    SGPropertyNode *n = prop->getNode("nasal"), *load;
+    if(!n)
+        return;
+
+    load = n->getNode("load");
+    _unload = n->getNode("unload");
+    if(!load && !_unload)
+        return;
+
+    _module = path;
+    const char *s = load ? load->getStringValue() : "";
+    nasalSys->createModule(_module.c_str(), _module.c_str(), s, strlen(s), _props);
+}
+
+FGNasalModelData::~FGNasalModelData()
+{
+    if(_module.empty())
+        return;
+
+    if(!nasalSys) {
+        SG_LOG(SG_NASAL, SG_ALERT, "Trying to run an <unload> script "
+                "without Nasal subsystem present.");
+        return;
+    }
+
+    if(_unload) {
+        const char *s = _unload->getStringValue();
+        nasalSys->createModule(_module.c_str(), _module.c_str(), s, strlen(s), _props);
+    }
+    nasalSys->deleteModule(_module.c_str());
+}
+
+
+
+// NasalXMLVisitor class: handles EasyXML visitor callback for parsexml()
+//
+NasalXMLVisitor::NasalXMLVisitor(naContext c, int argc, naRef* args) :
+    _c(naSubContext(c)),
+    _start_element(argc > 1 ? args[1] : naNil()),
+    _end_element(argc > 2 ? args[2] : naNil()),
+    _data(argc > 3 ? args[3] : naNil()),
+    _pi(argc > 4 ? args[4] : naNil())
+{
+}
+
+void NasalXMLVisitor::startElement(const char* tag, const XMLAttributes& a)
+{
+    if(naIsNil(_start_element)) return;
+    naRef attr = naNewHash(_c);
+    for(int i=0; i<a.size(); i++) {
+        naRef name = make_string(a.getName(i));
+        naRef value = make_string(a.getValue(i));
+        naHash_set(attr, name, value);
+    }
+    call(_start_element, 2, make_string(tag), attr);
+}
+
+void NasalXMLVisitor::endElement(const char* tag)
+{
+    if(!naIsNil(_end_element)) call(_end_element, 1, make_string(tag));
+}
+
+void NasalXMLVisitor::data(const char* str, int len)
+{
+    if(!naIsNil(_data)) call(_data, 1, make_string(str, len));
+}
+
+void NasalXMLVisitor::pi(const char* target, const char* data)
+{
+    if (!naIsNil(_pi)) call(_pi, 2, make_string(target), make_string(data));
+}
+
+void NasalXMLVisitor::call(naRef func, int num, naRef a, naRef b)
+{
+    naRef args[2];
+    args[0] = a;
+    args[1] = b;
+    naCall(_c, func, num, args, naNil(), naNil());
+    if(naGetError(_c))
+        naRethrowError(_c);
+}
+
+naRef NasalXMLVisitor::make_string(const char* s, int n)
+{
+    return naStr_fromdata(naNewString(_c), const_cast<char *>(s),
+                          n < 0 ? strlen(s) : n);
+}
+
+