feat: cache modified material

Close #94

Scripts/ModifiedMaterial.cs

@@ -0,0 +1,74 @@
+using System.Collections.Generic;
+using UnityEngine;
+
+namespace Coffee.UIParticleExtensions
+{
+    internal class ModifiedMaterial
+    {
+        private static readonly List<MatEntry> s_Entries = new List<MatEntry>();
+
+        public static Material Add(Material baseMat, Texture texture, int id)
+        {
+            MatEntry e;
+            for (var i = 0; i < s_Entries.Count; ++i)
+            {
+                e = s_Entries[i];
+                if (e.baseMat != baseMat || e.texture != texture || e.id != id) continue;
+                ++e.count;
+                return e.customMat;
+            }
+
+            e = new MatEntry();
+            e.count = 1;
+            e.baseMat = baseMat;
+            e.texture = texture;
+            e.id = id;
+            e.customMat = new Material(baseMat);
+            e.customMat.hideFlags = HideFlags.HideAndDontSave;
+            if (texture)
+                e.customMat.mainTexture = texture;
+            s_Entries.Add(e);
+            // Debug.LogFormat(">>>> ModifiedMaterial.Add -> count = {0} {1} {2} {3}", s_Entries.Count, baseMat, texture, id);
+            return e.customMat;
+        }
+
+        public static void Remove(Material customMat)
+        {
+            if (!customMat) return;
+
+            for (var i = 0; i < s_Entries.Count; ++i)
+            {
+                var e = s_Entries[i];
+                if (e.customMat != customMat) continue;
+                if (--e.count == 0)
+                {
+                    // Debug.LogFormat(">>>> ModifiedMaterial.Add -> count = {0} {1} {2} {3}", s_Entries.Count - 1, e.customMat, e.texture, e.id);
+                    DestroyImmediate(e.customMat);
+                    e.baseMat = null;
+                    e.texture = null;
+                    s_Entries.RemoveAt(i);
+                }
+
+                break;
+            }
+        }
+
+        private static void DestroyImmediate(Object obj)
+        {
+            if (!obj) return;
+            if (Application.isEditor)
+                Object.DestroyImmediate(obj);
+            else
+                Object.Destroy(obj);
+        }
+
+        private class MatEntry
+        {
+            public Material baseMat;
+            public Material customMat;
+            public int count;
+            public Texture texture;
+            public int id;
+        }
+    }
+}