Added feature: User can specify a directory that holds their VFX template assets (#34)

Added feature: User can specify a directory that holds their VFX template assets

Allow VFX artists to specify an asset directory that holds their own VFX templates aka Systems. This expands on the Systems functionality seen in the Node menu.

## How to use
The user directory is set in the menu: Edit -> Preferences -> Visual Effects -> User Systems
![image (1)](https://github.cds.internal.unity3d.com/storage/user/2318/files/d738c680-a1bb-11ea-94d4-68711743821d)

Open a VFX asset in the VFX Graph. Press spacebar to open the Node menu and note the new User Systems option.
![image (2)](https://github.cds.internal.unity3d.com/storage/user/2318/files/20891600-a1bc-11ea-8ab4-831989aef9df)

This option points to the User Systems directory specified by the user. This option will only show up if the user has set the directory to a valid location. It supports nested folders.
![image (3)](https://github.cds.internal.unity3d.com/storage/user/2318/files/4d3d2d80-a1bc-11ea-954f-4c29da91253f)

Compare this to the folder structure in Assets. Note that empty folders and folders not containing VFX assets are not displayed:
![image (4)](https://github.cds.internal.unity3d.com/storage/user/2318/files/7cec3580-a1bc-11ea-86e1-fa3154e108a2)

Author: tyanalunas

com.unity.visualeffectgraph/Editor/GraphView/VFXViewPreference.cs

@@ -110,16 +110,25 @@ public override void OnGUI(string searchContext)
                             vfxAsset.GetResource().GetOrCreateGraph().SetCompilationMode(m_ForceEditionCompilation ? VFXCompilationMode.Edition : VFXCompilationMode.Runtime);
                     }
 
+                    var userTemplateDirectory = EditorGUILayout.DelayedTextField(new GUIContent("User Systems", "Directory for user-generated VFX templates (e.g. Assets/VFX/Templates)"), VFXResources.defaultResources.userTemplateDirectory);
+
                     if (GUI.changed)
                     {
                         EditorPrefs.SetBool(experimentalOperatorKey, m_DisplayExperimentalOperator);
                         EditorPrefs.SetBool(extraDebugInfoKey, m_DisplayExtraDebugInfo);
                         EditorPrefs.SetBool(forceEditionCompilationKey, m_ForceEditionCompilation);
                         EditorPrefs.SetBool(advancedLogsKey, m_AdvancedLogs);
                         EditorPrefs.SetBool(allowShaderExternalizationKey, m_AllowShaderExternalization);
+                        userTemplateDirectory = userTemplateDirectory.Replace('\\', '/');
+                        userTemplateDirectory = userTemplateDirectory.TrimEnd(new char[] { '/' });
+                        userTemplateDirectory = userTemplateDirectory.TrimStart(new char[] { '/' });
+                        VFXResources.defaultResources.userTemplateDirectory = userTemplateDirectory;
                     }
                 }
 
+                if ((VFXResources.defaultResources.userTemplateDirectory.Length > 0) && (!System.IO.Directory.Exists(VFXResources.defaultResources.userTemplateDirectory)))
+                    EditorGUILayout.HelpBox("The specified User Systems directory does not exist in the project.", MessageType.Warning);
+
                 base.OnGUI(searchContext);
             }
         }

com.unity.visualeffectgraph/Editor/GraphView/Views/VFXNodeProvider.cs

@@ -223,11 +223,10 @@ protected override IEnumerable<Descriptor> GetDescriptors()
             }
             if (m_AcceptedTypes == null)
             {
-                var systemFiles = System.IO.Directory.GetFiles(VisualEffectAssetEditorUtility.templatePath).Where(t => Path.GetExtension(t) == VisualEffectResource.Extension).Select(t => t.Replace("\\", "/"));
+                AddTemplatesFromDirectory(VisualEffectAssetEditorUtility.templatePath, "System", ref descs);
 
-                var systemDesc = systemFiles.Select(t => new Descriptor() { modelDescriptor = t.Replace(VisualEffectGraphPackageInfo.fileSystemPackagePath, VisualEffectGraphPackageInfo.assetPackagePath), category = "System", name = System.IO.Path.GetFileNameWithoutExtension(t) });
-
-                descs = descs.Concat(systemDesc);
+                if ((VFXResources.defaultResources.userTemplateDirectory.Length > 0) && System.IO.Directory.Exists(VFXResources.defaultResources.userTemplateDirectory))
+                    AddTemplatesFromDirectory(VFXResources.defaultResources.userTemplateDirectory, "User Systems", ref descs);
             }
             var groupNodeDesc = new Descriptor()
             {
@@ -243,5 +242,21 @@ protected override IEnumerable<Descriptor> GetDescriptors()
             else
                 return descs.Where(t => m_Filter(t));
         }
+
+        protected void AddTemplatesFromDirectory(string directory, string menuCategory, ref IEnumerable<Descriptor> descriptors)
+        {
+            var subDirectories = System.IO.Directory.GetDirectories(directory);
+
+            Array.Sort(subDirectories, (x, y) => String.Compare(x, y, true));
+
+            foreach (var subDirectory in subDirectories)
+                AddTemplatesFromDirectory(subDirectory, subDirectory.Replace(directory,menuCategory), ref descriptors);
+
+            var discoveredTemplates = System.IO.Directory.GetFiles(directory).Where(t => Path.GetExtension(t) == VisualEffectResource.Extension).Select(t => t.Replace("\\", "/"));
+
+            var templateDescriptors = discoveredTemplates.Select(t => new Descriptor() { modelDescriptor = t, category = menuCategory.Replace("\\", "/"), name = System.IO.Path.GetFileNameWithoutExtension(t) });
+
+            descriptors = descriptors.Concat(templateDescriptors);
+        }
     }
 }

com.unity.visualeffectgraph/Editor/GraphView/Views/VFXView.cs

@@ -225,7 +225,9 @@ public VFXNodeController AddNode(VFXNodeProvider.Descriptor d, Vector2 mPos)
             {
                 string path = d.modelDescriptor as string;
 
-                if (!path.StartsWith(VisualEffectAssetEditorUtility.templatePath))
+                if(path.StartsWith(VisualEffectAssetEditorUtility.templatePath) || ((VFXResources.defaultResources.userTemplateDirectory.Length > 0) && path.StartsWith(VFXResources.defaultResources.userTemplateDirectory)) )
+                    CreateTemplateSystem(path, mPos, groupNode);
+                else
                 {
                     if (Path.GetExtension(path) == VisualEffectSubgraphOperator.Extension)
                     {
@@ -243,8 +245,6 @@ public VFXNodeController AddNode(VFXNodeProvider.Descriptor d, Vector2 mPos)
                         }
                     }
                 }
-                else
-                    CreateTemplateSystem(path, mPos, groupNode);
             }
             else if (d.modelDescriptor is GroupNodeAdder)
             {
@@ -1154,7 +1154,6 @@ void OnCompile()
             }
         }
 
-
         void OnSave()
         {
             OnCompile();

com.unity.visualeffectgraph/Editor/Utils/VFXResources.cs

@@ -149,6 +149,26 @@ public Mesh mesh
                     return defaultMesh;
                 }
             }
+
+            public string userTemplateDirectory
+            {
+                get
+                {
+                    LoadUserResourcesIfNeeded();
+                    if (s_Instance != null)
+                        return s_Instance.userTemplateDirectory;
+
+                    return "";
+                }
+
+                set
+                {
+                    if (s_Instance == null)
+                        s_Instance = FindObjectOfType<VFXResources>();
+                    if (s_Instance != null)
+                        s_Instance.userTemplateDirectory = value;
+                }
+            }
         }
 
         private static string defaultPath { get { return VisualEffectGraphPackageInfo.assetPackagePath + "/"; } }
@@ -283,6 +303,9 @@ static public Mesh defaultMesh {
         [SerializeField]
         Mesh mesh = null;
 
+        [SerializeField]
+        string userTemplateDirectory = "";
+
         static AnimationCurve defaultAnimationCurve;
         static Gradient defaultGradient;
         static Gradient defaultGradientMapRamp;