Allow Set Spawn Count & Set Spawn Time

TODO : List Spawn count in available variant

Author: PaulDemeulenaere

com.unity.visualeffectgraph/Editor/Expressions/VFXAttributeExpression.cs

@@ -98,7 +98,7 @@ struct VFXAttribute
         internal static readonly VFXAttribute StripAlive                     = new VFXAttribute("stripAlive", VFXValue.Constant(true)); // Internal attribute used to keep track of the state of the attached strip (TODO: Use a number to handle more tha 1 strip)
 
         public static readonly VFXAttribute[] AllAttribute = VFXReflectionHelper.CollectStaticReadOnlyExpression<VFXAttribute>(typeof(VFXAttribute));
-        public static readonly VFXAttribute[] AllAttributeReadOnly = new VFXAttribute[] { Seed, ParticleId, SpawnTime, ParticleIndexInStrip, SpawnIndex, StripIndex, ParticleCountInStrip };
+        public static readonly VFXAttribute[] AllAttributeReadOnly = new VFXAttribute[] { Seed, ParticleId, ParticleIndexInStrip, SpawnIndex, StripIndex, ParticleCountInStrip };
         public static readonly VFXAttribute[] AllAttributeWriteOnly = new VFXAttribute[] { EventCount };
         public static readonly VFXAttribute[] AllAttributeLocalOnly = new VFXAttribute[] { EventCount, ParticleIndexInStrip, StripIndex, ParticleCountInStrip };
 

com.unity.visualeffectgraph/Editor/Models/Blocks/Implementations/Spawn/VFXSpawnerSetAttribute.cs

@@ -7,10 +7,18 @@
 
 namespace UnityEditor.VFX.Block
 {
+    class AttributeProviderSpawner : IStringProvider
+    {
+        public string[] GetAvailableString()
+        {
+            return VFXAttribute.AllIncludingVariadicExceptWriteOnly.Concat(new[] { "spawnCount" }).ToArray();
+        }
+    }
+
     [VFXInfo(category = "Attribute", variantProvider = typeof(AttributeVariantReadWritableNoVariadic))]
     class VFXSpawnerSetAttribute : VFXAbstractSpawner
     {
-        [VFXSetting(VFXSettingAttribute.VisibleFlags.InInspector), StringProvider(typeof(AttributeProvider))]
+        [VFXSetting(VFXSettingAttribute.VisibleFlags.InInspector), StringProvider(typeof(AttributeProviderSpawner))]
         public string attribute = VFXAttribute.AllReadWritable.First();
 
         [VFXSetting(VFXSettingAttribute.VisibleFlags.InInspector)]
@@ -20,6 +28,8 @@ private VFXAttribute currentAttribute
         {
             get
             {
+                if (attribute == "spawnCount") //spawnCount isn't listed in attribute but it belongs to attribute in spawner.
+                    return new VFXAttribute("spawnCount", VFXValueType.Float);
                 return VFXAttribute.Find(attribute);
             }
         }