I had accidentally broken the raceXML construction - fixed it.

Fixed a few issues where boat didn't have nextMark/previousMark times under certain circumstances.
LatestMessages wasn't actually notifying properly - fixed.
The various XML readers now treat a string constructor as containing file contents, not file name - this was how it was mostly already used.
Fixed some issues in RaceXMLReader, including where element.getChildNodes() was used instead of element.getElementsByName(...).
Boat: changes speed to a doubleProperty. Changed leg to a Property<Leg>.
Race.lastFps is now an IntegerProperty.
Added breaks to the case statements in VisualiserInput. Whoops.
ResizableRaceCanvas now handles drawing the race boundary. Tidied up code a bit.
Removed ResizableRaceMap.

Started refactoring Sparkline. Currently doesn't work.

racevisionGame/src/main/java/visualiser/model/TrackPoint.java

@@ -7,17 +7,39 @@ import shared.model.GPSCoordinate;
  * A TrackPoint is a point plotted to display the track a
  * {@link VisualiserBoat Boat} has travelled in a race. <br>
  * TrackPoints are displayed on a
- * {@link seng302.Model.ResizableRaceCanvas ResizableRaceCanvas}, via the
- * {@link seng302.Controllers.RaceController RaceController}. <br>
+ * {@link ResizableRaceCanvas}, via the
+ * {@link visualiser.Controllers.RaceController}. <br>
  * Track points can be made visible or hidden via the RaceController's
- * {@link seng302.Model.Annotations Annotations}.
+ * {@link Annotations}.
  */
 public class TrackPoint {
+
+    /**
+     * The {@link GPSCoordinate} this {@link TrackPoint} corresponds to.
+     */
     private final GPSCoordinate coordinate;
+
+    /**
+     * The time the track point was created at, in milliseconds since unix epoch.
+     */
     private final long timeAdded;
+
+    /**
+     * The period of time, in milliseconds, over which the track point's alpha should diminish to a floor value of {@link #minAlpha}.
+     */
     private final long expiry;
+
+    /**
+     * The minimum alpha to draw the track point with.
+     */
     private final double minAlpha;
 
+    /**
+     * The diameter to draw the track point with.
+     */
+    private final double diameter;
+
+
     /**
      * Creates a new track point with fixed GPS coordinates and time, to reach minimum opacity on expiry.
      *
@@ -29,9 +51,12 @@ public class TrackPoint {
         this.coordinate = coordinate;
         this.timeAdded = timeAdded;
         this.expiry = expiry;
+
         this.minAlpha = 0.1;
+        this.diameter = 5d;
     }
 
+
     /**
      * Gets the position of the point on physical race map.
      *
@@ -44,10 +69,23 @@ public class TrackPoint {
     /**
      * Gets opacity of point scaled by age in proportion to expiry, between 1 and minimum opacity inclusive.
      *
-     * @return greater of minimum opacity and scaled opacity
+     * @return Greater of minimum opacity and scaled opacity.
      */
     public double getAlpha() {
-        return Double.max(minAlpha, 1.0 - (double) (System.currentTimeMillis() - timeAdded) / expiry);
+
+        //Calculate how much the alpha should be attenuated by elapsed time.
+
+        //Elapsed time.
+        long elapsedTime = System.currentTimeMillis() - this.timeAdded;
+
+        //Proportion of expiry period that has elapsed. (E.g., 2.5 means that 5 times the period has elapsed.)
+        double elapsedProportion = ((double) elapsedTime) / this.expiry;
+
+        //As the alpha diminishes from 1 down to a floor, we take the complement of this value. This may be negative.
+        double calculatedAlpha = 1.0 - elapsedProportion;
+
+        //We then take the max of the minAlpha and calculatedAlpha so that it doesn't go past our floor value.
+        return Double.max(this.minAlpha, calculatedAlpha);
     }
 
     /**
@@ -58,4 +96,13 @@ public class TrackPoint {
     public long getTimeAdded() {
         return timeAdded;
     }
+
+
+    /**
+     * Returns the diameter to draw the track point with.
+     * @return The diameter to draw the track point with.
+     */
+    public double getDiameter() {
+        return diameter;
+    }
 }