Added validator and updated brush

src/PixiEditor.ChangeableDocument/Changeables/Graph/Nodes/Brushes/BrushOutputNode.cs

@@ -86,6 +86,9 @@ public class BrushOutputNode : Node
         "M0.25 99.4606C0.25 99.4606 60.5709 79.3294 101.717 99.4606C147.825 122.019 199.75 99.4606 199.75 99.4606";
 
     public const int YOffsetInPreview = -88;
+    public const string UseCustomStampBlenderProperty = "UseCustomStampBlender";
+    public const string CustomStampBlenderCodeProperty = "CustomStampBlender";
+    public const string StampBlendModeProperty = "StampBlendMode";
 
     private VectorPath? previewVectorPath;
 
@@ -99,13 +102,14 @@ public class BrushOutputNode : Node
         Transform = CreateInput<Matrix3X3>("Transform", "TRANSFORM", Matrix3X3.Identity);
         ImageBlendMode = CreateInput<Drawie.Backend.Core.Surfaces.BlendMode>("BlendMode", "BLEND_MODE",
             Drawie.Backend.Core.Surfaces.BlendMode.SrcOver);
-        StampBlendMode = CreateInput<Drawie.Backend.Core.Surfaces.BlendMode>("StampBlendMode", "STAMP_BLEND_MODE",
+        StampBlendMode = CreateInput<Drawie.Backend.Core.Surfaces.BlendMode>(StampBlendModeProperty, "STAMP_BLEND_MODE",
             Drawie.Backend.Core.Surfaces.BlendMode.SrcOver);
 
-        UseCustomStampBlender = CreateInput<bool>("UseCustomStampBlender", "USE_CUSTOM_STAMP_BLENDER", false);
+        UseCustomStampBlender = CreateInput<bool>(UseCustomStampBlenderProperty, "USE_CUSTOM_STAMP_BLENDER", false);
 
         CustomStampBlenderCode =
-            CreateInput<string>("CustomStampBlenderCode", "CUSTOM_STAMP_BLENDER_CODE", DefaultBlenderCode);
+            CreateInput<string>(CustomStampBlenderCodeProperty, "CUSTOM_STAMP_BLENDER_CODE", DefaultBlenderCode)
+                .WithRules(validator => validator.Custom(ValidateBlenderCode));
         CanReuseStamps = CreateInput<bool>("CanReuseStamps", "CAN_REUSE_STAMPS", false);
 
         Pressure = CreateInput<float>("Pressure", "PRESSURE", 1f);
@@ -119,6 +123,23 @@ public class BrushOutputNode : Node
         Previous = CreateInput<IReadOnlyNodeGraph>("Previous", "PREVIOUS", null);
     }
 
+    private ValidatorResult ValidateBlenderCode(object? value)
+    {
+        if (value is string code)
+        {
+            Blender? blender = Blender.CreateFromString(code, out string? error);
+            if (blender != null)
+            {
+                blender.Dispose();
+                return new ValidatorResult(true, null);
+            }
+
+            return new ValidatorResult(false, error);
+        }
+
+        return new ValidatorResult(false, "Blender code must be a string.");
+    }
+
     protected override void OnExecute(RenderContext context)
     {
         if (Content.Value != null)

src/PixiEditor/ViewModels/Document/Nodes/Brushes/BrushOutputNodeViewModel.cs

@@ -1,5 +1,9 @@
-using PixiEditor.ChangeableDocument.Changeables.Graph.Nodes.Brushes;
+using Drawie.Backend.Core.Bridge;
+using PixiEditor.ChangeableDocument.Changeables.Graph.Nodes.Brushes;
+using PixiEditor.Models.Events;
+using PixiEditor.Models.Handlers;
 using PixiEditor.ViewModels.Nodes;
+using PixiEditor.ViewModels.Nodes.Properties;
 
 namespace PixiEditor.ViewModels.Document.Nodes.Brushes;
 
@@ -10,5 +14,17 @@ internal class BrushOutputNodeViewModel : NodeViewModel<BrushOutputNode>
     {
         InputPropertyMap[BrushOutputNode.BrushNameProperty].SocketEnabled = false;
         InputPropertyMap[BrushOutputNode.FitToStrokeSizeProperty].SocketEnabled = false;
+        InputPropertyMap[BrushOutputNode.UseCustomStampBlenderProperty].ValueChanged += OnValueChanged;
+        if(InputPropertyMap[BrushOutputNode.CustomStampBlenderCodeProperty] is StringPropertyViewModel codeProperty)
+        {
+            codeProperty.IsVisible = (bool)InputPropertyMap[BrushOutputNode.UseCustomStampBlenderProperty].Value;
+            codeProperty.Kind = DrawingBackendApi.Current.ShaderImplementation.ShaderLanguageExtension;
+        }
+    }
+
+    private void OnValueChanged(INodePropertyHandler property, NodePropertyValueChangedArgs args)
+    {
+        InputPropertyMap[BrushOutputNode.CustomStampBlenderCodeProperty].IsVisible = (bool)args.NewValue;
+        InputPropertyMap[BrushOutputNode.StampBlendModeProperty].IsVisible = !(bool)args.NewValue;
     }
 }