Add Lat/Lon grid MapStructure layer.

Nasal/canvas/map/GRID.lcontroller

@@ -0,0 +1,103 @@
+# See: http://wiki.flightgear.org/MapStructure
+# Class things:
+var name = 'GRID';
+var parents = [SymbolLayer.Controller];
+var __self__ = caller(0)[0];
+SymbolLayer.Controller.add(name, __self__);
+SymbolLayer.add(name, {
+	parents: [MultiSymbolLayer],
+	type: name, # Symbol type
+	df_controller: __self__, # controller to use by default -- this one
+	df_options: { # default configuration options
+		granularity_lon: 0.25,
+		granularity_lat: 0.25,
+	}
+});
+var new = func(layer) {
+	var m = {
+		parents: [__self__],
+		layer: layer,
+		map: layer.map,
+		listeners: [],
+		last_lat: -999,
+		last_lon: -999,
+		last_range: -999,
+		last_result: [],
+	};
+	layer.searcher._equals = func(l,r) 0; # TODO: create model objects instead?
+
+	m.addVisibilityListener();
+	return m;
+};
+var del = func() {
+	foreach (var l; me.listeners)
+		removelistener(l);
+};
+
+var searchCmd = func() {
+
+	var lines = [];
+	var delta_lon = me.layer.options.granularity_lon;
+	var delta_lat = me.layer.options.granularity_lat;
+
+	# Find the nearest lat/lon line to the map position.  If we were just displaying
+	# integer lat/lon lines, this would just be rounding.
+	var lat = delta_lat * math.round(me.layer.map.getLat() / delta_lat);
+  var lon = delta_lon * math.round(me.layer.map.getLon() / delta_lon);
+	var range = me.layer.map.getRange();
+
+	# Return early if no significant change in lat/lon/range - implies no additional
+	# grid lines required
+	if ((lat == me.last_lat) and (lon == me.last_lon) and (range == me.last_range)) return me.last_result;
+
+	# Determine number of degrees of lat/lon we need to display based on range
+	# 60nm = 1 degree latitude, degree range for longitude is dependent on latitude.
+	var lon_range = math.ceil(geo.Coord.new(me.layer.map.getPosCoord()).apply_course_distance(90.0, range * globals.NM2M).lon() - lon) * 2;
+	var lat_range = math.ceil(range/60.0) * 2;
+
+	for (var x = (lon - lon_range); x <= (lon + lon_range); x += delta_lon) {
+		var coords = [];
+
+		# We could do a simple line from start to finish, but depending on projection,
+		# the line may not be straight.
+		for (var y = (lat - lat_range); y <= (lat + lat_range); y +=  delta_lat) {
+			append(coords, {lon:x, lat:y});
+		}
+
+		append(lines, {
+			id: x,
+			type: "lon",
+			path: coords,
+			equals: func(o){
+				return (me.id == o.id and me.type == o.type); # We only display one line of each lat/lon
+			}
+		});
+	}
+
+	# Lines of latitude
+	for (var y = (lat - lat_range); y <= (lat + lat_range); y += delta_lat) {
+		var coords = [];
+
+		# We could do a simple line from start to finish, but depending on projection,
+		# the line may not be straight.
+		for (var x = (lon - lon_range); x <= (lon + lon_range); x += delta_lon) {
+			append(coords, {lon:x, lat:y});
+		}
+
+		append(lines, {
+			id: y,
+			type: "lat",
+			path: coords,
+			equals: func(o){
+				return (me.id == o.id and me.type == o.type); # We only display one line of each lat/lon
+			}
+		});
+	}
+
+	me.last_lat = lat;
+	me.last_lon = lon;
+	me.last_range = range;
+	me.last_result = lines;
+
+	return lines;
+};

Nasal/canvas/map/GRID.symbol

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+# See: http://wiki.flightgear.org/MapStructure
+
+# Class things:
+var name = 'GRID';
+var parents = [LineSymbol];
+var __self__ = caller(0)[0];
+LineSymbol.makeinstance( name, __self__ );
+
+SymbolLayer.get(name).df_style = { # style to use by default
+	line_width: 1,
+	color: [0.5,0.5,0.5],
+	dash_array: [5,15,5,15],
+};
+
+var init = func {
+	me.element.setColor(me.layer.style.color)
+	.setStrokeLineWidth(me.layer.style.line_width)
+	.setStrokeDashArray(me.layer.style.dash_array);
+};