feat: add imgui extesion

Source/Utils/ImGuiExtension.cs

@@ -0,0 +1,59 @@
+using ImGuiNET;
+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using System.Text;
+
+namespace UImGui
+{
+	internal static unsafe class ImGuiExtension
+	{
+		private static readonly HashSet<IntPtr> _managedAllocations = new HashSet<IntPtr>(); // TODO: Check if yet IntPtr has boxing when comparing equality (see original version)
+
+		internal static void SetBackendPlatformName(this ImGuiIOPtr io, string name)
+		{
+			if (io.NativePtr->BackendPlatformName != (byte*)0)
+			{
+				if (_managedAllocations.Contains((IntPtr)io.NativePtr->BackendPlatformName))
+				{
+					Marshal.FreeHGlobal(new IntPtr(io.NativePtr->BackendPlatformName));
+				}
+				io.NativePtr->BackendPlatformName = (byte*)0;
+			}
+			if (name != null)
+			{
+				int byteCount = Encoding.UTF8.GetByteCount(name);
+				byte* nativeName = (byte*)Marshal.AllocHGlobal(byteCount + 1);
+				int offset = Utils.GetUtf8(name, nativeName, byteCount);
+
+				nativeName[offset] = 0;
+
+				io.NativePtr->BackendPlatformName = nativeName;
+				_managedAllocations.Add((IntPtr)nativeName);
+			}
+		}
+
+		internal static void SetIniFilename(this ImGuiIOPtr io, string name)
+		{
+			if (io.NativePtr->IniFilename != (byte*)0)
+			{
+				if (_managedAllocations.Contains((IntPtr)io.NativePtr->IniFilename))
+				{
+					Marshal.FreeHGlobal((IntPtr)io.NativePtr->IniFilename);
+				}
+				io.NativePtr->IniFilename = (byte*)0;
+			}
+			if (name != null)
+			{
+				int byteCount = Encoding.UTF8.GetByteCount(name);
+				byte* nativeName = (byte*)Marshal.AllocHGlobal(byteCount + 1);
+				int offset = Utils.GetUtf8(name, nativeName, byteCount);
+
+				nativeName[offset] = 0;
+
+				io.NativePtr->IniFilename = nativeName;
+				_managedAllocations.Add((IntPtr)nativeName);
+			}
+		}
+	}
+}