Improving the Graph Visualiser for new API

- PlayableGraph API (Timeline 5.6 alpha)
- Bug fixing and robustness improvements
- Workflow simplification
- Based on the work of Catherine Proulx

Author: HQ\chacha

Assets/Editor/GraphVisualizer.meta

@@ -0,0 +1,70 @@
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+
+namespace GraphVisualizer
+{
+    public abstract class Graph : IEnumerable<Node>
+    {
+        private readonly List<Node> m_Nodes = new List<Node>();
+
+        public ReadOnlyCollection<Node> nodes
+        {
+            get { return m_Nodes.AsReadOnly(); }
+        }
+
+        protected class NodeWeight
+        {
+            public object node { get; set; }
+            public float weight { get; set; }
+        }
+
+        // Derived class should specify the children of a given node.
+        protected abstract IEnumerable<Node> GetChildren(Node node);
+
+        // Derived class should implement how to populate this graph (usually by calling AddNodeHierarchy()).
+        protected abstract void Populate();
+
+        public void AddNodeHierarchy(Node root)
+        {
+            AddNode(root);
+
+            IEnumerable<Node> children = GetChildren(root);
+            if (children == null)
+                return;
+
+            foreach (Node child in children)
+            {
+                root.AddChild(child);
+                AddNodeHierarchy(child);
+            }
+        }
+
+        public void AddNode(Node node)
+        {
+            m_Nodes.Add(node);
+        }
+
+        public void Clear()
+        {
+            m_Nodes.Clear();
+        }
+
+        public void Refresh()
+        {
+            // TODO optimize?
+            Clear();
+            Populate();
+        }
+
+        public IEnumerator<Node> GetEnumerator()
+        {
+            return m_Nodes.GetEnumerator();
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return m_Nodes.GetEnumerator();
+        }
+    }
+}

Assets/Editor/GraphVisualizer/Graph.meta

@@ -0,0 +1,45 @@
+using System.Collections.Generic;
+using UnityEngine;
+
+namespace GraphVisualizer
+{
+    // Interface for a generic graph layout.
+    public interface IGraphLayout
+    {
+        IEnumerable<Vertex> vertices { get; }
+        IEnumerable<Edge> edges { get; }
+
+        bool leftToRight { get; }
+
+        void CalculateLayout(Graph graph);
+    }
+
+    public class Edge
+    {
+        // Indices in the vertex array of the layout algorithm.
+        public Edge(Vertex src, Vertex dest)
+        {
+            source = src;
+            destination = dest;
+        }
+
+        public Vertex source { get; private set; }
+
+        public Vertex destination { get; private set; }
+    }
+
+    // One vertex is associated to each node in the graph.
+    public class Vertex
+    {
+        // Center of the node in the graph layout.
+        public Vector2 position { get; set; }
+
+        // The Node represented by the vertex.
+        public Node node { get; private set; }
+
+        public Vertex(Node node)
+        {
+            this.node = node;
+        }
+    }
+}