C#: Add source generator for signals as events

Changed the signal declaration signal to:

```
// The following generates a MySignal event
[Signal] public delegate void MySignalEventHandler(int param);
```

1 files changed, 70 insertions, 0 deletions

diff --git a/modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/ScriptSerializationGenerator.cs b/modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/ScriptSerializationGenerator.cs
index 3a7086a2be..224a2d0a50 100644
--- a/modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/ScriptSerializationGenerator.cs
+++ b/modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/ScriptSerializationGenerator.cs
@@ -1,3 +1,4 @@
+using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using Microsoft.CodeAnalysis;
@@ -120,10 +121,39 @@ namespace Godot.SourceGenerators
             var godotClassProperties = propertySymbols.WhereIsGodotCompatibleType(typeCache).ToArray();
             var godotClassFields = fieldSymbols.WhereIsGodotCompatibleType(typeCache).ToArray();
 
+            var signalDelegateSymbols = members
+                .Where(s => s.Kind == SymbolKind.NamedType)
+                .Cast<INamedTypeSymbol>()
+                .Where(namedTypeSymbol => namedTypeSymbol.TypeKind == TypeKind.Delegate)
+                .Where(s => s.GetAttributes()
+                    .Any(a => a.AttributeClass?.IsGodotSignalAttribute() ?? false));
+
+            List<GodotSignalDelegateData> godotSignalDelegates = new();
+
+            foreach (var signalDelegateSymbol in signalDelegateSymbols)
+            {
+                if (!signalDelegateSymbol.Name.EndsWith(ScriptSignalsGenerator.SignalDelegateSuffix))
+                    continue;
+
+                string signalName = signalDelegateSymbol.Name;
+                signalName = signalName.Substring(0,
+                    signalName.Length - ScriptSignalsGenerator.SignalDelegateSuffix.Length);
+
+                var invokeMethodData = signalDelegateSymbol
+                    .DelegateInvokeMethod?.HasGodotCompatibleSignature(typeCache);
+
+                if (invokeMethodData == null)
+                    continue;
+
+                godotSignalDelegates.Add(new(signalName, signalDelegateSymbol, invokeMethodData.Value));
+            }
+
             source.Append(
                 "    protected override void SaveGodotObjectData(global::Godot.Bridge.GodotSerializationInfo info)\n    {\n");
             source.Append("        base.SaveGodotObjectData(info);\n");
 
+            // Save properties
+
             foreach (var property in godotClassProperties)
             {
                 string propertyName = property.PropertySymbol.Name;
@@ -135,6 +165,8 @@ namespace Godot.SourceGenerators
                     .Append(");\n");
             }
 
+            // Save fields
+
             foreach (var field in godotClassFields)
             {
                 string fieldName = field.FieldSymbol.Name;
@@ -146,12 +178,27 @@ namespace Godot.SourceGenerators
                     .Append(");\n");
             }
 
+            // Save signal events
+
+            foreach (var signalDelegate in godotSignalDelegates)
+            {
+                string signalName = signalDelegate.Name;
+
+                source.Append("        info.AddSignalEventDelegate(GodotInternal.SignalName_")
+                    .Append(signalName)
+                    .Append(", this.backing_")
+                    .Append(signalName)
+                    .Append(");\n");
+            }
+
             source.Append("    }\n");
 
             source.Append(
                 "    protected override void RestoreGodotObjectData(global::Godot.Bridge.GodotSerializationInfo info)\n    {\n");
             source.Append("        base.RestoreGodotObjectData(info);\n");
 
+            // Restore properties
+
             foreach (var property in godotClassProperties)
             {
                 string propertyName = property.PropertySymbol.Name;
@@ -171,6 +218,8 @@ namespace Godot.SourceGenerators
                     .Append(";\n");
             }
 
+            // Restore fields
+
             foreach (var field in godotClassFields)
             {
                 string fieldName = field.FieldSymbol.Name;
@@ -190,6 +239,27 @@ namespace Godot.SourceGenerators
                     .Append(";\n");
             }
 
+            // Restore signal events
+
+            foreach (var signalDelegate in godotSignalDelegates)
+            {
+                string signalName = signalDelegate.Name;
+                string signalDelegateQualifiedName = signalDelegate.DelegateSymbol.FullQualifiedName();
+
+                source.Append("        if (info.TryGetSignalEventDelegate<")
+                    .Append(signalDelegateQualifiedName)
+                    .Append(">(GodotInternal.SignalName_")
+                    .Append(signalName)
+                    .Append(", out var _value_")
+                    .Append(signalName)
+                    .Append("))\n")
+                    .Append("            this.backing_")
+                    .Append(signalName)
+                    .Append(" = _value_")
+                    .Append(signalName)
+                    .Append(";\n");
+            }
+
             source.Append("    }\n");
 
             source.Append("}\n"); // partial class