1 files changed, 77 insertions, 0 deletions
diff --git a/source/com/c2kernel/graph/controller/StartVertexController.java b/source/com/c2kernel/graph/controller/StartVertexController.java
new file mode 100755
index 0000000..0dc959c
--- /dev/null
+++ b/source/com/c2kernel/graph/controller/StartVertexController.java
@@ -0,0 +1,77 @@
+package com.c2kernel.graph.controller;
+
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.util.Observable;
+import java.util.Observer;
+
+import javax.swing.JButton;
+
+import com.c2kernel.graph.event.SelectionChangedEvent;
+import com.c2kernel.graph.model.GraphModelManager;
+import com.c2kernel.graph.model.Vertex;
+
+
+// The start vertex controller is responsible for selecting
+// the vertex at the start of the graph.
+//
+// The controller listens to:
+//     * The graph model to determine if there is a single
+//       vertex selected
+//     * The start vertex button
+//
+// The controller modifies:
+//     * The graph model to select the start vertex
+//     * The start button to enable it only when there is a
+//       single vertex selected
+public class StartVertexController implements Observer, ActionListener
+{
+    private GraphModelManager mGraphModelManager  = null;
+    private JButton           mStartButton        = null;
+
+
+    public void setGraphModelManager(GraphModelManager graphModelManager)
+    {
+        mGraphModelManager = graphModelManager;
+        mGraphModelManager.addObserver(this);
+    }
+
+
+    public void setStartButton(JButton startButton)
+    {
+        mStartButton = startButton;
+        mStartButton.addActionListener(this);
+    }
+
+
+    public void update(Observable o, Object arg)
+    {
+        SelectionChangedEvent event            = null;
+        Vertex[]              selectedVertices = null;
+
+        // If the selected vertex has changed
+        if(arg instanceof SelectionChangedEvent && mStartButton != null)
+        {
+            event            = (SelectionChangedEvent)arg;
+            selectedVertices = event.mSelection.mVertices;
+
+            if(selectedVertices == null)
+            {
+                mStartButton.setEnabled(false);
+            }
+            else if (mGraphModelManager.isEditable())
+            {
+                mStartButton.setEnabled(selectedVertices.length == 1);
+            }
+        }
+    }
+
+
+    public void actionPerformed(ActionEvent ae)
+    {
+        if(mGraphModelManager != null)
+        {
+            mGraphModelManager.getModel().setSelectedVertexToBeStart();
+        }
+    }
+}