Add new method getFirstSpot to TreeUtils

* Convenience method to retrieve the first spot of a branch spot

src/main/java/org/mastodon/util/TreeUtils.java

@@ -39,6 +39,7 @@
 import org.mastodon.graph.Vertex;
 import org.mastodon.mamut.model.Model;
 import org.mastodon.mamut.model.Spot;
+import org.mastodon.mamut.model.branch.BranchSpot;
 
 public class TreeUtils
 {
@@ -255,4 +256,18 @@ public static int getMaxTimepoint( final Model model )
 			max = Math.max( max, spot.getTimepoint() );
 		return max;
 	}
+
+	/**
+	 * Gets the first {@link Spot} within the given {@link BranchSpot}.
+	 * @param model the {@link Model} to which the {@link BranchSpot} belongs
+	 * @param branchSpot the {@link BranchSpot} to query
+	 * @return the first {@link Spot}
+	 */
+	public static Spot getFirstSpot( final Model model, final BranchSpot branchSpot )
+	{
+		Spot ref = model.getGraph().vertexRef();
+		Spot first = model.getBranchGraph().getFirstLinkedVertex( branchSpot, ref );
+		model.getGraph().releaseRef( ref );
+		return first;
+	}
 }

src/test/java/org/mastodon/util/TreeUtilsTest.java

@@ -191,4 +191,14 @@ public void testGetMaxTimepoint()
 		assertEquals( 3, TreeUtils.getMaxTimepoint( new ExampleGraph1().getModel() ) );
 		assertEquals( 7, TreeUtils.getMaxTimepoint( new ExampleGraph2().getModel() ) );
 	}
+
+	@Test
+	public void testGetFirstSpot()
+	{
+		ExampleGraph1 exampleGraph1 = new ExampleGraph1();
+		assertEquals( exampleGraph1.spot0, TreeUtils.getFirstSpot( exampleGraph1.getModel(), exampleGraph1.branchSpotA ) );
+
+		ExampleGraph2 exampleGraph2 = new ExampleGraph2();
+		assertEquals( exampleGraph2.spot5, TreeUtils.getFirstSpot( exampleGraph2.getModel(), exampleGraph2.branchSpotD ) );
+	}
 }