feat: preview the ParticleSystem playback when selecting a UIParticle in the Editor

Editor/UIParticleEditor.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text.RegularExpressions;
@@ -8,6 +9,7 @@ using UnityEngine;
 using UnityEngine.Profiling;
 using UnityEngine.UI;
 using Coffee.UIParticleInternal;
+using Object = UnityEngine.Object;
 #if UNITY_2021_2_OR_NEWER
 using UnityEditor.Overlays;
 #else
@@ -66,6 +68,7 @@ namespace Coffee.UIExtensions
         private ReorderableList _ro;
         private bool _showMax;
         private bool _is3DScaleMode;
+        private GameObject[] _gameObjects;
 
         private static readonly HashSet<Shader> s_Shaders = new HashSet<Shader>();
 #if UNITY_2018 || UNITY_2019
@@ -183,6 +186,13 @@ namespace Coffee.UIExtensions
                                  y.hasMultipleDifferentValues ||
                                  z.hasMultipleDifferentValues;
             }
+
+            // Add temporary ParticleSystem for preview if enabled.
+            if (UIParticleProjectSettings.previewOnSelect)
+            {
+                _gameObjects = targets.OfType<UIParticle>().Select(x => x.gameObject).ToArray();
+                ParticleSystemPreviewSystem.Register(_gameObjects);
+            }
         }
 
         /// <summary>
@@ -344,6 +354,10 @@ namespace Coffee.UIExtensions
                 }
             }
 #endif
+
+            // Remove the temporary ParticleSystem.
+            ParticleSystemPreviewSystem.DrawWarningForTemporary(_gameObjects);
+
             Profiler.EndSample();
         }
 
@@ -482,7 +496,7 @@ namespace Coffee.UIExtensions
 #endif
         }
 
-        private static bool FixButton(bool show, string text)
+        private static bool FixButton(bool show, string text, GUIContent buttonText = null)
         {
             if (!show) return false;
             using (new EditorGUILayout.HorizontalScope(GUILayout.ExpandWidth(true)))
@@ -490,7 +504,7 @@ namespace Coffee.UIExtensions
                 EditorGUILayout.HelpBox(text, MessageType.Warning, true);
                 using (new EditorGUILayout.VerticalScope())
                 {
-                    return GUILayout.Button(s_ContentFix, GUILayout.Width(30));
+                    return GUILayout.Button(buttonText ?? s_ContentFix, GUILayout.ExpandWidth(false));
                 }
             }
         }

Runtime/Internal/Utilities/Misc.cs

@@ -48,15 +48,10 @@ namespace Coffee.UIParticleInternal
         {
             if (obj == null) return;
 #if UNITY_EDITOR
-            if (Application.isEditor)
-            {
-                Object.DestroyImmediate(obj);
-            }
-            else
-#endif
-            {
+            Object.DestroyImmediate(obj, true);
+#else
             Object.Destroy(obj);
-            }
+#endif
         }
 
         [Conditional("UNITY_EDITOR")]

Runtime/ParticleSystemPreviewer.cs

@@ -0,0 +1,237 @@
+using System.Collections.Generic;
+using System.Linq;
+using Coffee.UIParticleInternal;
+using UnityEditor;
+using UnityEngine;
+
+namespace Coffee.UIExtensions
+{
+    [Icon("Packages/com.coffee.ui-particle/Editor/UIParticleIcon.png")]
+    [ExecuteAlways]
+    internal class ParticleSystemPreviewer : MonoBehaviour
+    {
+        // Do nothing.
+    }
+
+#if UNITY_EDITOR
+    [CustomEditor(typeof(ParticleSystemPreviewer))]
+    [CanEditMultipleObjects]
+    internal class ParticleSystemPreviewerEditor : Editor
+    {
+        private GameObject[] _gameObjects;
+
+        private void OnEnable()
+        {
+            _gameObjects = targets.OfType<ParticleSystemPreviewer>().Select(x => x.gameObject).ToArray();
+            ParticleSystemPreviewSystem.Register(_gameObjects);
+        }
+
+        public override void OnInspectorGUI()
+        {
+            base.OnInspectorGUI();
+            ParticleSystemPreviewSystem.DrawWarningForTemporary(_gameObjects);
+            ParticleSystemPreviewSystem.DrawWarningForPermanent(_gameObjects);
+        }
+    }
+
+    /// <summary>
+    /// This class manages temporary ParticleSystems for preview purposes.
+    /// When previewing in the editor, it is common to place an empty ParticleSystem as the root, but it consumes memory at runtime if included in the build.
+    /// The temporary ParticleSystems created by this class only exist when the specified GameObject is selected, and are automatically deleted when the selection is cleared.
+    /// </summary>
+    internal class ParticleSystemPreviewSystem : ScriptableSingleton<ParticleSystemPreviewSystem>
+    {
+        private const HideFlags k_TemporaryHideFlags = HideFlags.DontSave | HideFlags.NotEditable;
+
+        [SerializeField]
+        private List<GameObject> m_PreviewObjects = new List<GameObject>();
+
+#if UNITY_2019_3_OR_NEWER
+        [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.SubsystemRegistration)]
+#endif
+        [InitializeOnLoadMethod]
+        public static void Initialize()
+        {
+            instance.OnSelectionChanged();
+
+            Selection.selectionChanged -= instance.OnSelectionChanged;
+            Selection.selectionChanged += instance.OnSelectionChanged;
+        }
+
+        /// <summary>
+        /// Adds a temporary ParticleSystem to the specified GameObject for preview purposes.
+        /// </summary>
+        public static void Register(GameObject[] targets)
+        {
+            foreach (var target in targets)
+            {
+                Register(target);
+            }
+        }
+
+        /// <summary>
+        /// Adds a temporary ParticleSystem to the specified GameObject for preview purposes.
+        /// </summary>
+        public static void Register(GameObject target)
+        {
+            if (!target) return;
+            if (EditorApplication.isPlaying) return;
+            if (instance.m_PreviewObjects.Contains(target)) return;
+            if (target.TryGetComponent<ParticleSystem>(out var ps))
+            {
+                if (ps.hideFlags == k_TemporaryHideFlags)
+                {
+                    RegisterParticleSystem(ps);
+                }
+
+                return;
+            }
+
+            // Create temporary ParticleSystem for preview.
+            RegisterParticleSystem(target.AddComponent<ParticleSystem>());
+        }
+
+        /// <summary>
+        /// Removes the temporary ParticleSystem associated with the specified GameObject.
+        /// </summary>
+        /// <param name="target"></param>
+        public static void Unregister(GameObject target)
+        {
+            if (!target) return;
+
+            var index = instance.m_PreviewObjects.IndexOf(target);
+            if (index < 0) return;
+
+            instance.m_PreviewObjects.RemoveAt(index);
+            if (HasTemporaryParticleSystem(target))
+            {
+                RemoveParticleSystem(target);
+            }
+        }
+
+        private static void RegisterParticleSystem(ParticleSystem ps)
+        {
+            if (!ps) return;
+            if (EditorApplication.isPlaying) return;
+
+            ps.hideFlags = k_TemporaryHideFlags;
+
+            var emission = ps.emission;
+            emission.enabled = false;
+            var shape = ps.shape;
+            shape.enabled = false;
+
+            if (ps.TryGetComponent<ParticleSystemRenderer>(out var psr))
+            {
+                psr.enabled = false;
+                psr.hideFlags = k_TemporaryHideFlags;
+            }
+
+            instance.m_PreviewObjects.Add(ps.gameObject);
+            EditorUtility.SetDirty(ps.gameObject);
+        }
+
+        /// <summary>
+        /// Removes the temporary ParticleSystem associated with the specified GameObject.
+        /// </summary>
+        /// <param name="target"></param>
+        private static void RemoveParticleSystem(GameObject target)
+        {
+            if (target.TryGetComponent<ParticleSystem>(out var ps))
+            {
+                Misc.DestroyImmediate(ps);
+                EditorUtility.SetDirty(target);
+            }
+
+            if (target.TryGetComponent<ParticleSystem>(out var psr))
+            {
+                Misc.DestroyImmediate(psr);
+                EditorUtility.SetDirty(target);
+            }
+        }
+
+        /// <summary>
+        /// Checks if the specified GameObject has a temporary ParticleSystem.
+        /// </summary>
+        private static bool HasTemporaryParticleSystem(GameObject target)
+        {
+            return target
+                   && instance.m_PreviewObjects.Contains(target)
+                   && target.TryGetComponent<ParticleSystem>(out var ps)
+                   && ps.hideFlags == k_TemporaryHideFlags;
+        }
+
+        /// <summary>
+        /// Checks if the specified GameObject has a permanent ParticleSystem.
+        /// </summary>
+        private static bool HasPermanentParticleSystem(GameObject target)
+        {
+            return target
+                   && target.TryGetComponent<ParticleSystem>(out var ps)
+                   && ps.hideFlags != k_TemporaryHideFlags;
+        }
+
+        private void OnSelectionChanged()
+        {
+            var selectedGameObjects = Selection.gameObjects;
+            for (var i = m_PreviewObjects.Count - 1; 0 <= i; i--)
+            {
+                var go = m_PreviewObjects[i];
+                if (!go)
+                {
+                    m_PreviewObjects.RemoveAt(i);
+                }
+                else if (EditorApplication.isPlaying && !selectedGameObjects.Contains(go))
+                {
+                    Unregister(go);
+                }
+            }
+        }
+
+        public static void DrawWarningForTemporary(GameObject[] gameObjects)
+        {
+            if (gameObjects == null || gameObjects.Length == 0 || !gameObjects.Any(HasTemporaryParticleSystem)) return;
+
+            if (WarningButton("The temporary ParticleSystem for preview is attached.\n" +
+                              "It will be removed when exiting edit mode.", "Remove"))
+            {
+                foreach (var go in gameObjects)
+                {
+                    if (HasTemporaryParticleSystem(go))
+                    {
+                        RemoveParticleSystem(go);
+                    }
+                }
+            }
+        }
+
+        public static void DrawWarningForPermanent(GameObject[] gameObjects)
+        {
+            if (gameObjects == null || gameObjects.Length == 0 || !gameObjects.Any(HasPermanentParticleSystem)) return;
+
+            if (WarningButton("The permanent ParticleSystem is attached.\n" +
+                              "It will be included in build.", "Remove"))
+            {
+                foreach (var go in gameObjects)
+                {
+                    if (HasPermanentParticleSystem(go))
+                    {
+                        RemoveParticleSystem(go);
+                        Unregister(go);
+                        Register(go);
+                    }
+                }
+            }
+        }
+
+        private static bool WarningButton(string message, string buttonText)
+        {
+            EditorGUILayout.BeginHorizontal();
+            EditorGUILayout.HelpBox(message, MessageType.Warning, true);
+            var clicked = GUILayout.Button(EditorGUIUtility.TrTempContent(buttonText));
+            EditorGUILayout.EndHorizontal();
+            return clicked;
+        }
+    }
+#endif
+}

Runtime/ParticleSystemPreviewer.cs.meta

@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: b171deb49fb7b471291108ad7e1c9baa
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

Runtime/UIParticle.cs

@@ -545,7 +545,10 @@ namespace Coffee.UIExtensions
             {
                 var ps = particles[i];
                 if (!ps
+#if UNITY_EDITOR
+                    || (ps.hideFlags & HideFlags.DontSave) != 0 // Dummy ParticleSystems for preview.
                     || ps.gameObject.CompareTag("EditorOnly") // Ignore "EditorOnly" tagged ParticleSystems.
+#endif
                     || ps.GetComponentInParent<UIParticle>(true) != this) // Ignore ParticleSystems that are not under this UIParticle.
                 {
                     particles.RemoveAt(i);

Runtime/UIParticleProjectSettings.cs

@@ -25,10 +25,16 @@ namespace Coffee.UIExtensions
         [SerializeField]
         private bool m_HideGeneratedObjects = true;
 
-        public static HideFlags globalHideFlags => instance.m_HideGeneratedObjects
+        [Tooltip("When selecting UIParticle, a temporary ParticleSystem is generated for preview.")]
+        [SerializeField]
+        private bool m_PreviewOnSelect = true;
+
+        internal static HideFlags globalHideFlags => instance.m_HideGeneratedObjects
             ? HideFlags.DontSave | HideFlags.NotEditable | HideFlags.HideInHierarchy | HideFlags.HideInInspector
             : HideFlags.DontSave | HideFlags.NotEditable;
 
+        internal static bool previewOnSelect => instance.m_PreviewOnSelect;
+
 #if UNITY_EDITOR
         [SettingsProvider]
         private static SettingsProvider CreateSettingsProvider()