Implemented DebugBlendModeNode to try out blend modes from drawing backend

src/PixiEditor.ChangeableDocument/Changeables/Graph/Nodes/DebugBlendModeNode.cs

@@ -0,0 +1,54 @@
+using PixiEditor.ChangeableDocument.Rendering;
+using DrawingApiBlendMode = PixiEditor.DrawingApi.Core.Surface.BlendMode;
+using PixiEditor.DrawingApi.Core.Surface.ImageData;
+using PixiEditor.DrawingApi.Core.Surface.PaintImpl;
+using PixiEditor.Numerics;
+
+namespace PixiEditor.ChangeableDocument.Changeables.Graph.Nodes;
+
+// TODO: Add based on debug mode, not debug build.
+#if DEBUG
+public class DebugBlendModeNode : Node
+{
+    private Paint _paint = new();
+    
+    public InputProperty<Surface?> Dst { get; }
+
+    public InputProperty<Surface?> Src { get; }
+
+    public InputProperty<DrawingApiBlendMode> BlendMode { get; }
+
+    public OutputProperty<Surface> Result { get; }
+
+    public DebugBlendModeNode()
+    {
+        Dst = CreateInput<Surface?>(nameof(Dst), "Dst", null);
+        Src = CreateInput<Surface?>(nameof(Src), "Src", null);
+        BlendMode = CreateInput(nameof(BlendMode), "Blend Mode", DrawingApiBlendMode.SrcOver);
+
+        Result = CreateOutput<Surface>(nameof(Result), "Result", null);
+    }
+    
+    protected override Surface? OnExecute(RenderingContext context)
+    {
+        if (Dst.Value is not { } dst || Src.Value is not { } src)
+            return null;
+
+        var size = new VecI(Math.Max(src.Size.X, dst.Size.X), int.Max(src.Size.Y, dst.Size.Y));
+        var workingSurface = new Surface(size);
+
+        workingSurface.DrawingSurface.Canvas.DrawSurface(dst.DrawingSurface, 0, 0, context.BlendModeOpacityPaint);
+
+        _paint.BlendMode = BlendMode.Value;
+        workingSurface.DrawingSurface.Canvas.DrawSurface(src.DrawingSurface, 0, 0, _paint);
+        
+        Result.Value = workingSurface;
+
+        return workingSurface;
+    }
+
+    public override bool Validate() => true;
+
+    public override Node CreateCopy() => new DebugBlendModeNode();
+}
+#endif