corrected direction

src/index.mjs

@@ -1,13 +1,19 @@
 import * as Files from "./modules/file.js"
 import * as Draw from "./modules/draw.js"
 
-var HEADING=0;     // DESIRED HEADING
+var HEADING  = 0;     // DESIRED HEADING
 var _HEADING = 0;  // DIAL HEADING
-var FPS = 50 ; // SPEED DIAL REFRESHS
+var FPS = 25 ; // SPEED DIAL REFRESHS
+var DIRECTION = 0;
 
 export function SetHeading( hdg )
 {
-    HEADING = 360 - hdg;
+    HEADING =  360 - mod(hdg , 360);
+    if( HEADING ==  0 )
+    {
+            HEADING = 360
+    }
+    DIRECTION = direction()
 }
 export function Compass() {
     var canvas = document.querySelector("canvas");
@@ -23,14 +29,12 @@ export function Compass() {
 
     img.onload = function () {
         setInterval(function () {
-            // Need a proper function to drive
-            if( HEADING != _HEADING )
-                _HEADING += 1;
+            rotate();
 
             ctx.save(); //saves the state of canvas
             ctx.clearRect(0, 0, canvas.width, canvas.height); //clear the canvas
             ctx.translate(canvas.width/2, canvas.height/2); //let's translate
-            ctx.rotate(Math.PI / 180 * (_HEADING )); //increment the angle and rotate the image
+            ctx.rotate( radians( _HEADING ) );
             ctx.translate(-(canvas.width/2), -(canvas.height/2)); //let's translate
             Draw.drawImageScaled(img , ctx );
             ctx.restore();
@@ -39,3 +43,37 @@ export function Compass() {
         }, FPS);
     }
 }
+
+function rotate()
+{
+    if( Math.abs( HEADING % 360 )== Math.abs( _HEADING % 360 ) ) return ;
+
+    _HEADING =  mod(_HEADING , 360);
+
+    _HEADING += DIRECTION;
+
+    //console.log( "Target Heading    = " + _HEADING );
+    //console.log( "Requested Heading = " + HEADING);
+}
+
+function direction()
+{
+    var a = ( _HEADING % 360 ) - HEADING
+    a = (a + 180) % 360
+
+
+    console.log( "Direction " + a);
+
+    return ( a < 0 ) ? -1 : 1;
+}
+
+function mod( a, n )
+{
+    return a - Math.floor( a / n) * n ;
+
+}
+
+function radians( degree )
+{
+   return  degree * Math.PI / 180;
+}