Fix: Scroller was not operating correctly in the non-linear scrolling…

… region, although only really noticable at the exterimities

- DD-969

js/dataTables.scroller.js

@@ -419,7 +419,7 @@ $.extend( Scroller.prototype, {
 			}
 		}
 
-		if ( typeof animate == 'undefined' || animate )
+		if ( animate === undefined || animate )
 		{
 			this.s.ani = ani;
 			$(this.dom.scroller).animate( {
@@ -429,7 +429,7 @@ $.extend( Scroller.prototype, {
 				// the final scroll event fired
 				setTimeout( function () {
 					that.s.ani = false;
-				}, 25 );
+				}, 250 );
 			} );
 		}
 		else
@@ -786,11 +786,11 @@ $.extend( Scroller.prototype, {
 		if ( val < magic ) {
 			return val;
 		}
-		else if ( dir === 'virtualToPhysical' && val > heights.virtual - magic ) {
+		else if ( dir === 'virtualToPhysical' && val >= heights.virtual - magic ) {
 			diff = heights.virtual - val;
 			return heights.scroll - diff;
 		}
-		else if ( dir === 'physicalToVirtual' && val > heights.scroll - magic ) {
+		else if ( dir === 'physicalToVirtual' && val >= heights.scroll - magic ) {
 			diff = heights.scroll - val;
 			return heights.virtual - diff;
 		}
@@ -803,17 +803,12 @@ $.extend( Scroller.prototype, {
 		// causing a kink in the scrolling ratio. It does mean the scrollbar is
 		// non-linear, but with such massive data sets, the scrollbar is going
 		// to be a best guess anyway
-		var xMax = dir === 'virtualToPhysical' ?
-			heights.virtual :
-			heights.scroll;
-		var yMax = dir === 'virtualToPhysical' ?
-			heights.scroll :
-			heights.virtual;
-
-		var m = (yMax - magic) / (xMax - magic);
+		var m = (heights.virtual - magic - magic) / (heights.scroll - magic - magic);
 		var c = magic - (m*magic);
 
-		return (m*val) + c;
+		return dir === 'virtualToPhysical' ?
+			(val-c) / m :
+			(m*val) + c;
 	},
 
 	/**