Canvas Layer Created

- Canvas is created via layering.
- Resizable canvas is now a seperate abstract class
#story[782]

visualiser/src/main/java/seng302/Model/ResizableCanvas.java

@@ -0,0 +1,55 @@
+package seng302.Model;
+
+import javafx.scene.canvas.Canvas;
+import javafx.scene.canvas.GraphicsContext;
+
+/**
+ * Created by fwy13 on 4/05/17.
+ */
+public abstract class ResizableCanvas extends Canvas {
+    protected GraphicsContext gc;
+
+    public ResizableCanvas(){
+        this.gc = this.getGraphicsContext2D();
+        // Redraw canvas when size changes.
+        widthProperty().addListener(evt -> draw());
+        heightProperty().addListener(evt -> draw());
+
+    }
+
+    abstract void draw();
+
+
+    /**
+     * Set the Canvas to resizable.
+     *
+     * @return That the Canvas is resizable.
+     */
+    @Override
+    public boolean isResizable() {
+        return true;
+    }
+
+    /**
+     * Returns the preferred width of the Canvas
+     *
+     * @param width of canvas
+     * @return Returns the width of the Canvas
+     */
+    @Override
+    public double prefWidth(double width) {
+        return getWidth();
+    }
+
+    /**
+     * Returns the preferred height of the Canvas
+     *
+     * @param height of canvas
+     * @return Returns the height of the Canvas
+     */
+    @Override
+    public double prefHeight(double height) {
+        return getHeight();
+    }
+
+}