io: use default attribs rather than a hard-coded number for globals identification

gui/tutorial/aircraft: use io.read_properties()/io.write_properties()

Nasal/aircraft.nas

@@ -432,15 +432,14 @@ var data = {
 		size(me.catalog) or return;
 		printlog("debug", "saving aircraft data to ", me.path);
 		me.signalN.setBoolValue(1);
-		var args = props.Node.new({ "filename": me.path });
-		var data = args.getNode("data", 1);
+		var data = props.Node.new();
 		foreach (var c; me.catalog) {
 			if (c[0] == `/`)
 				c = substr(c, 1);
 
 			props.copy(props.globals.getNode(c, 1), data.getNode(c, 1));
 		}
-		fgcommand("savexml", args);
+		io.write_properties(me.path, data);
 	},
 	add : func(p...) {
 		foreach (var n; props.nodeList(p))
@@ -574,10 +573,7 @@ var livery = {
 		foreach (var file; directory(path)) {
 			if (substr(file, -4) != ".xml")
 				continue;
-			var n = props.Node.new({ filename : path ~ file });
-			fgcommand("loadxml", n);
-			n = n.getNode("data");
-
+			var n = io.read_properties(path ~ file);
 			var name = n.getNode(me.name_path);
 			var index = n.getNode(me.sort_path);
 			if (name == nil or index == nil)
@@ -624,7 +620,7 @@ var livery = {
 # in the remote aircraft accordingly.
 #
 # SYNOPSIS:
-#	livery_update(<livery-dir> [, <interval:10> [, <func>]]);
+#	livery_update.new(<livery-dir> [, <interval:10> [, <func>]]);
 #
 #	<livery-dir> ... directory with livery files, relative to $FG_ROOT
 #	<interval>   ... checking interval in seconds (default: 10)
@@ -667,8 +663,7 @@ var livery_update = {
 		me.running or return;
 		var file = me.fileN.getValue();
 		if (file != nil and file != me.last) {
-			fgcommand("loadxml", props.Node.new({ filename: me.dir ~ file ~ ".xml",
-					targetnode: me.root }));
+			io.read_properties(me.dir ~ file ~ ".xml", me.root);
 			me.last = file;
 			if (me.callback != nil)
 				me.callback(file);
@@ -721,10 +716,7 @@ var formation = {
 		foreach (var file; directory(path)) {
 			if (substr(file, -4) != ".xml")
 				continue;
-			var n = props.Node.new({ filename : path ~ file });
-			fgcommand("loadxml", n);
-			n = n.getNode("data");
-
+			var n = io.read_properties(path ~ file);
 			var name = n.getNode(me.name_path);
 			var index = n.getNode(me.sort_path);
 			if (name == nil or index == nil)

Nasal/gui.nas

@@ -225,8 +225,7 @@ var Dialog = {
             me.close();
 
         me.prop.removeChildren();
-        fgcommand("loadxml", props.Node.new({"filename": getprop("/sim/fg-root") ~ "/" ~ me.path,
-                "targetnode": me.prop.getPath()}));
+        io.read_properties(getprop("/sim/fg-root") ~ "/" ~ me.path, me.prop);
 
         var n = me.prop.getNode("name");
         if (n == nil)

Nasal/io.nas

@@ -87,11 +87,10 @@ var read_properties = func(path, target = nil) {
 
 # Write XML file in FlightGear's native <PropertyList> format.
 # Returns the filename on success or nil on error. If the source
-# is a props.Node, then a unique node attribute number is used to
-# determine whether the tree is a subtree of the global tree, in
-# which case the branch is writen directly from that tree, as this
-# yields a more accurate result. (The attributes are "readable"
-# + "writable" + the lowest unused bit.)
+# is a props.Node that refers to a node in the main tree, then
+# the data are directly written from the tree, yielding a more
+# accurate result. Otherwise the data need to be copied first,
+# which may slightly change node types (FLOAT becomes DOUBLE etc.)
 #
 # Usage:   io.write_properties(<filename>, <props.Node or property-path>);
 #
@@ -102,9 +101,10 @@ var read_properties = func(path, target = nil) {
 #     io.write_properties("/tmp/foo.xml", "/sim/model");
 #
 var write_properties = func(path, prop) {
-    var attr = props.globals.getAttribute("last") * 2 + 3;
-    props.globals.setAttribute(attr);
     var args = props.Node.new({ filename: path });
+    # default attributes of a new node plus the lowest unused bit
+    var attr = args.getAttribute() + args.getAttribute("last") * 2;
+    props.globals.setAttribute(attr);
     if(isa(prop, props.Node)) {
         for(var root = prop; (var p = root.getParent()) != nil;)
             root = p;

Nasal/tutorial.nas

@@ -468,10 +468,7 @@ var dialog = func {
 #
 var load = func(file, index = 0) {
 	props.globals.getNode("/sim/tutorials", 1).removeChild("tutorial", index);
-	fgcommand("loadxml", props.Node.new({
-		"filename": getprop("/sim/fg-root") ~ "/" ~ file,
-		"targetnode": "/sim/tutorials/tutorial[" ~ index ~ "]/",
-	}));
+	io.read_properties(getprop("/sim/fg-root") ~ "/" ~ file, "/sim/tutorials/tutorial[" ~ index ~ "]/");
 }