Add Timer class for simplify use maketimer() function with single shot

addon-main.nas

@@ -42,6 +42,7 @@ var main = func(addon) {
 #
 var loadExtraNasalFiles = func (addon) {
     var modules = [
+        "nasal/timer",
         "nasal/aircraft",
         "nasal/message",
         "nasal/dialogs/route",

addon-menubar-items.xml

@@ -79,11 +79,9 @@
                     <command>nasal</command>
                     <script><![CDATA[
                         # Run stopAerotow() with a delay to ensure that the engine sound turns off
-                        var timer = maketimer(1, func () {
+                        aerotow.Timer.new().singleShot(1, aerotow.g_Aerotow, func () {
                             aerotow.g_Aerotow.stopAerotow();
                         });
-                        timer.singleShot = 1;
-                        timer.start();
                     ]]></script>
                 </binding>
             </item>

nasal/aerotow.nas

@@ -51,8 +51,6 @@ var Aerotow = {
     #
     # Function for restart AI scenario with delay when the sound has to stop.
     #
-    # Return 1 on successful, otherwise 0.
-    #
     restartAerotow: func () {
         me.message.success("Aerotow on the way");
 
@@ -60,11 +58,9 @@ var Aerotow = {
         setprop(me.addonNodePath ~ "/addon-devel/sound/enable", 0);
 
         # Wait a second for the engine sound to turn off
-        var timer = maketimer(1, func () {
+        Timer.new().singleShot(1, me, func () {
             me.unloadScenario();
         });
-        timer.singleShot = 1;
-        timer.start();
     },
 
     #
@@ -76,11 +72,9 @@ var Aerotow = {
         }
 
         # Start aerotow with delay to avoid duplicate engine sound playing
-        var timer = maketimer(1, func () {
+        Timer.new().singleShot(1, me, func () {
             me.startAerotow();
         });
-        timer.singleShot = 1;
-        timer.start();
     },
 
     #

nasal/timer.nas

@@ -0,0 +1,41 @@
+#
+# Aerotow Everywhere - Add-on for FlightGear
+#
+# Written and developer by Roman Ludwicki (PlayeRom, SP-ROM)
+#
+# Copyright (C) 2022 Roman Ludwicki
+#
+# Aerotow Everywhere is an Open Source project and it is licensed
+# under the GNU Public License v3 (GPLv3)
+#
+
+#
+# Class Timer for wrapping maketimer()
+#
+var Timer = {
+    #
+    # Constructor
+    #
+    new: func () {
+        return { parents: [Timer] };
+    },
+
+    #
+    # Run timer as single shot
+    #
+    # delaySec - Delay in seconds for execute timer's callback.
+    # self - Specifying what any "me" references in the function being called will refer to.
+    # callback - Function to be called after given delay.
+    #
+    # Return timer handler object
+    #
+    singleShot: func (delaySec, self, callback) {
+        var timer = maketimer(delaySec, self, func () {
+            callback();
+        });
+        timer.singleShot = 1;
+        timer.start();
+
+        return timer;
+    },
+};