MonoGame backend sample for ImGui.NET (https://github.com/mellinoe/ImGui.NET)

Game1.cs

using System;
using System.Runtime.InteropServices;
using ImGuiNET;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Input;

using Vector2 = ImGuiNET.Vector2;
using Vector3 = ImGuiNET.Vector3;
using Vector4 = ImGuiNET.Vector4;

namespace ImGuiMG
{
    public class Game1 : Game
    {
        private readonly GraphicsDeviceManager _graphics;

        private ImGuiMg _imgui;

        private int _pressCount;
        private Vector4 _buttonColor = new Vector4(55f / 255f, 155f / 255f, 1f, 1f);
        private bool _mainWindowOpened;
        private float _sliderVal;
        private Vector3 _positionValue = new Vector3(500);
        public readonly IntPtr TextInputBuffer;
        public readonly int TextInputBufferLength;

        private readonly MemoryEditor _memoryEditor = new MemoryEditor();
        private readonly byte[] _memoryEditorData;
 
        public unsafe Game1()
        {
            _graphics = new GraphicsDeviceManager(this);
            Content.RootDirectory = "Content";
            IsMouseVisible = true;
            Window.AllowUserResizing = true;

            IsFixedTimeStep = false;
            _graphics.SynchronizeWithVerticalRetrace = false;

            _graphics.PreferredBackBufferWidth = 960;
            _graphics.PreferredBackBufferHeight = 540;

            TextInputBufferLength = 1024;
            TextInputBuffer = Marshal.AllocHGlobal(TextInputBufferLength);
            var ptr = (long*)TextInputBuffer.ToPointer();
            for (var i = 0; i < 1024 / sizeof(long); i++)
                ptr[i] = 0;


            _memoryEditorData = new byte[1024];
            var rnd = new Random();
            for (var i = 0; i < _memoryEditorData.Length; i++)
                _memoryEditorData[i] = (byte) rnd.Next(255);
        }

        protected override void LoadContent()
        {
            _imgui = new ImGuiMg(Window, GraphicsDevice);

            /*var frc = new FrameRateCounter(this);
            frc.Position = new Microsoft.Xna.Framework.Vector2(10f, 500f);
            frc.Font = Content.Load<SpriteFont>("font");
            Components.Add(frc);*/
        }

        protected override void Dispose(bool disposing)
        {
            _imgui.Dispose();
            base.Dispose(disposing);
        }

        protected override void Update(GameTime gameTime)
        {
            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed || Keyboard.GetState().IsKeyDown(Keys.Escape))
                Exit();

            _imgui.Update(gameTime);
            SubmitImGuiStuff();

            base.Update(gameTime);
        }

        protected override void Draw(GameTime gameTime)
        {
            GraphicsDevice.Clear(Color.CornflowerBlue);

            _imgui.Draw();

            base.Draw(gameTime);
        }

        private unsafe void SubmitImGuiStuff()
        {
            ImGui.GetStyle().WindowRounding = 0;

            var pp = GraphicsDevice.PresentationParameters;
            ImGui.SetNextWindowSize(new Vector2(pp.BackBufferWidth - 20, pp.BackBufferHeight - 50), SetCondition.Once);
            ImGui.SetNextWindowPosCenter(SetCondition.Always);

            ImGui.BeginWindow("Hello from ImGui!", ref _mainWindowOpened, WindowFlags.Default);

            ImGui.BeginMainMenuBar();
            if (ImGui.BeginMenu("Help"))
            {
                if (ImGui.MenuItem("About", "Ctrl-Alt-A", false, true))
                {
                }
                ImGui.EndMenu();
            }
            ImGui.EndMainMenuBar();


            var pos = ImGui.GetIO().MousePosition;
            var leftPressed = ImGui.GetIO().MouseDown[0];
            ImGui.Text("Current mouse position: " + pos + ". Pressed=" + leftPressed);

            if (ImGui.Button("Increment the counter."))
                _pressCount += 1;

            ImGui.Text($"Button pressed {_pressCount} times.", new Vector4(0, 1, 1, 1));

            ImGui.Text("Input some text:");
            ImGui.InputTextMultiline(string.Empty,
                TextInputBuffer, (uint) TextInputBufferLength,
                new Vector2(360, 240),
                InputTextFlags.Default,
                OnTextEdited);

            ImGui.SliderFloat("SlidableValue", ref _sliderVal, -50f, 100f, $"{_sliderVal:##0.00}", 1.0f);
            ImGui.DragVector3("Vector3", ref _positionValue, -100, 100);

            if (ImGui.TreeNode("First Item"))
            {
                ImGui.Text("Word!");
                ImGui.TreePop();
            }
            if (ImGui.TreeNode("Second Item"))
            {
                ImGui.ColorButton(_buttonColor, false, true);
                if (ImGui.Button("Push me to change color", new Vector2(120, 30)))
                {
                    _buttonColor = new Vector4(_buttonColor.Y + .25f, _buttonColor.Z, _buttonColor.X, _buttonColor.W);
                    if (_buttonColor.X > 1.0f)
                    {
                        _buttonColor.X -= 1.0f;
                    }
                }

                ImGui.TreePop();
            }

            if (ImGui.Button("Press me!", new Vector2(100, 30)))
                ImGuiNative.igOpenPopup("SmallButtonPopup");

            if (ImGui.BeginPopup("SmallButtonPopup"))
            {
                ImGui.Text("Here's a popup menu.");
                ImGui.Text("With two lines.");

                ImGui.EndPopup();
            }

            if (ImGui.Button("Open Modal window"))
                ImGui.OpenPopup("ModalPopup");
            if (ImGui.BeginPopupModal("ModalPopup"))
            {
                ImGui.Text("You can't press on anything else right now.");
                ImGui.Text("You are stuck here.");
                if (ImGui.Button("OK", new Vector2(0, 0))) { }
                ImGui.SameLine();
                ImGui.Dummy(100f, 0f);
                ImGui.SameLine();
                if (ImGui.Button("Please go away", new Vector2(0, 0))) { ImGui.CloseCurrentPopup(); }

                ImGui.EndPopup();
            }

            ImGui.Text("I have a context menu.");
            if (ImGui.BeginPopupContextItem("ItemContextMenu"))
            {
                if (ImGui.Selectable("How's this for a great menu?")) { }
                ImGui.Selectable("Just click somewhere to get rid of me.");
                ImGui.EndPopup();
            }

            ImGui.EndWindow();

            _memoryEditor.Draw("Memory editor", _memoryEditorData, _memoryEditorData.Length);
        }

        public unsafe int OnTextEdited(TextEditCallbackData* data)
        {
            var currentEventChar = (char)data->EventChar;
            return 0;
        }
    }
}

ImGuiMg.cs

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;

namespace ImGuiNET
{
    public sealed class ImGuiMg : IDisposable
    {
        private readonly GraphicsDevice _graphicsDevice;
        private readonly List<Texture2D> _textures;
        private readonly RasterizerState _rasterizerState;
        private readonly SpriteEffect _spriteEffect;
        private KeyboardState _prevKeyState;

        private int _sFontTexture;
        private float _wheelPosition;
        private readonly float _scaleFactor;

        public ImGuiMg(GameWindow gw, GraphicsDevice gd)
        {
            _graphicsDevice = gd;
            _textures = new List<Texture2D>();
            _rasterizerState = new RasterizerState
            {
                CullMode = CullMode.None,
                ScissorTestEnable = true
            };
            _spriteEffect = new SpriteEffect(gd);
 
            int desiredWidth = 960, desiredHeight = 540;
            
            _scaleFactor = (float) gd.PresentationParameters.BackBufferWidth / desiredWidth;

            ImGui.GetIO().FontAtlas.AddDefaultFont();

            SetKeyMappings();
            gw.TextInput += OnKeyPress;

            CreateDeviceObjects();
        }

        #region Keys

        private void OnKeyPress(object sender, TextInputEventArgs e)
        {
            Console.Write("Char typed: " + e.Character);
            ImGui.AddInputCharacter(e.Character);
        }

        private static unsafe void SetKeyMappings()
        {
            var io = ImGui.GetIO();
            io.KeyMap[GuiKey.Tab] = (int)Keys.Tab;
            io.KeyMap[GuiKey.LeftArrow] = (int)Keys.Left;
            io.KeyMap[GuiKey.RightArrow] = (int)Keys.Right;
            io.KeyMap[GuiKey.UpArrow] = (int)Keys.Up;
            io.KeyMap[GuiKey.DownArrow] = (int)Keys.Down;
            io.KeyMap[GuiKey.PageUp] = (int)Keys.PageUp;
            io.KeyMap[GuiKey.PageDown] = (int)Keys.PageDown;
            io.KeyMap[GuiKey.Home] = (int)Keys.Home;
            io.KeyMap[GuiKey.End] = (int)Keys.End;
            io.KeyMap[GuiKey.Delete] = (int)Keys.Delete;
            io.KeyMap[GuiKey.Backspace] = (int)Keys.Back;
            io.KeyMap[GuiKey.Enter] = (int)Keys.Enter;
            io.KeyMap[GuiKey.Escape] = (int)Keys.Escape;
            io.KeyMap[GuiKey.A] = (int)Keys.A;
            io.KeyMap[GuiKey.C] = (int)Keys.C;
            io.KeyMap[GuiKey.V] = (int)Keys.V;
            io.KeyMap[GuiKey.X] = (int)Keys.X;
            io.KeyMap[GuiKey.Y] = (int)Keys.Y;
            io.KeyMap[GuiKey.Z] = (int)Keys.Z;
        }

        private static void UpdateKeys(KeyboardState prev, KeyboardState current)
        {
            // Keys down
            foreach (var k in current.GetPressedKeys())
                ImGui.GetIO().KeysDown[(int) k] = true;

            // Keys up
            foreach (var k in prev.GetPressedKeys())
            {
                if (!current.GetPressedKeys().Contains(k))
                    ImGui.GetIO().KeysDown[(int) k] = false;
            }

            UpdateModifiers(current);
        }

        private static void UpdateModifiers(KeyboardState state)
        {
            var io = ImGui.GetIO();
            io.AltPressed = state.IsKeyDown(Keys.LeftAlt) || state.IsKeyDown(Keys.RightAlt);
            io.CtrlPressed = state.IsKeyDown(Keys.LeftControl) || state.IsKeyDown(Keys.RightControl);
            io.ShiftPressed = state.IsKeyDown(Keys.LeftShift) || state.IsKeyDown(Keys.RightShift);
        }

        #endregion

        private unsafe void CreateDeviceObjects()
        {
            var io = ImGui.GetIO();

            // Build texture atlas
            var texData = io.FontAtlas.GetTexDataAsRGBA32();
            var tex = new Texture2D(_graphicsDevice, texData.Width, texData.Height);
            if (texData.BytesPerPixel != 4)
                throw new Exception();
            var pixelCount = texData.Width * texData.Height;
            var pixelData = new Color[pixelCount];
            for (var i = 0; i < pixelCount; i++)
                pixelData[i] = new Color((int) texData.Pixels[4 * i], (int) texData.Pixels[4 * i + 1],
                    (int) texData.Pixels[4 * i + 2], (int) texData.Pixels[4 * i + 3]);
            tex.SetData(pixelData);
            _sFontTexture = _textures.Count;
            _textures.Add(tex);
            io.FontAtlas.SetTexID(_sFontTexture);
            // Store the texture identifier in the ImFontAtlas substructure.
            io.FontAtlas.SetTexID(_sFontTexture);

            // Cleanup (don't clear the input data if you want to append new fonts later)
            //io.Fonts->ClearInputData();
            io.FontAtlas.ClearTexData();
        }

        public void Update(GameTime gameTime)
        {
            var io = ImGui.GetIO();
            io.DeltaTime = (float) gameTime.ElapsedGameTime.TotalSeconds;
            UpdateImGuiInput(io);

            var pp = _graphicsDevice.PresentationParameters;
            io.DisplaySize = new Vector2(pp.BackBufferWidth, pp.BackBufferHeight);
            io.DisplayFramebufferScale = new Vector2(_scaleFactor);

            ImGui.NewFrame();
        }

        public unsafe void Draw()
        {
            ImGui.Render();
            var data = ImGui.GetDrawData();
            RenderImDrawData(data);
        }

        private void UpdateImGuiInput(IO io)
        {
            var kbState = Keyboard.GetState();
            UpdateKeys(_prevKeyState, kbState);

            var mouseState = Mouse.GetState();

            var windowPoint = mouseState.Position;
            io.MousePosition = new Vector2(windowPoint.X / io.DisplayFramebufferScale.X, windowPoint.Y / io.DisplayFramebufferScale.Y);

            io.MouseDown[0] = mouseState.LeftButton == ButtonState.Pressed;
            io.MouseDown[1] = mouseState.RightButton == ButtonState.Pressed;
            io.MouseDown[2] = mouseState.MiddleButton == ButtonState.Pressed;

            float newWheelPos = mouseState.ScrollWheelValue;
            var delta = newWheelPos - _wheelPosition;
            _wheelPosition = newWheelPos;
            io.MouseWheel = delta;

            _prevKeyState = kbState;
        }

        private unsafe void RenderImDrawData(DrawData* drawData)
        {
            if (drawData == null)
            {
                Console.WriteLine("No frame rendered for ImGUI.NET, but draw was called.");
                return;
            }

            var pp = _graphicsDevice.PresentationParameters;
            // Rendering
            var displayW = pp.BackBufferWidth;
            var displayH = pp.BackBufferHeight;

            var clearColor = new Vector4(114f / 255f, 144f / 255f, 154f / 255f, 1.0f);
            _graphicsDevice.Viewport = new Viewport(0, 0, displayW, displayH);
            _graphicsDevice.Clear(new Color(clearColor.X, clearColor.Y, clearColor.Z, clearColor.W));

            // We are using the OpenGL fixed pipeline to make the example code simpler to read!
            // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled, vertex/texcoord/color pointers.
            _graphicsDevice.BlendState = BlendState.NonPremultiplied;
            _graphicsDevice.RasterizerState = _rasterizerState;
            _graphicsDevice.DepthStencilState = DepthStencilState.None;

            // Handle cases of screen coordinates != from framebuffer coordinates (e.g. retina displays)
            var io = ImGui.GetIO();
            ImGui.ScaleClipRects(drawData, io.DisplayFramebufferScale);

            // Render command lists

            for (var n = 0; n < drawData->CmdListsCount; n++)
            {
                var cmdList = drawData->CmdLists[n];
                var vtxBuffer = (DrawVert*)cmdList->VtxBuffer.Data;
                var idxBuffer = (ushort*)cmdList->IdxBuffer.Data;

                var vertices = new VertexPositionColorTexture[cmdList->VtxBuffer.Size];
                for (var i = 0; i < vertices.Length; i++)
                {
                    vertices[i] = new VertexPositionColorTexture(
                        new Microsoft.Xna.Framework.Vector3(vtxBuffer[i].pos.X, vtxBuffer[i].pos.Y, 0),
                        new Color(vtxBuffer[i].col),
                        new Microsoft.Xna.Framework.Vector2(vtxBuffer[i].uv.X, vtxBuffer[i].uv.Y));
                }

                _spriteEffect.CurrentTechnique.Passes[0].Apply();

                for (var cmdI = 0; cmdI < cmdList->CmdBuffer.Size; cmdI++)
                {
                    var pcmd = &(((DrawCmd*)cmdList->CmdBuffer.Data)[cmdI]);
                    if (pcmd->UserCallback != IntPtr.Zero)
                    {
                        throw new NotImplementedException();
                    }
                    else
                    {
                        _graphicsDevice.Textures[0] = _textures[pcmd->TextureId.ToInt32()];
                        _graphicsDevice.ScissorRectangle = new Rectangle(
                            (int)pcmd->ClipRect.X,
                            (int)pcmd->ClipRect.Y,
                            (int)(pcmd->ClipRect.Z - pcmd->ClipRect.X),
                            (int)(pcmd->ClipRect.W - pcmd->ClipRect.Y));
                        var indices = new short[pcmd->ElemCount];
                        for (var i = 0; i < indices.Length; i++) { indices[i] = (short) idxBuffer[i]; }
                        _graphicsDevice.DrawUserIndexedPrimitives(
                            PrimitiveType.TriangleList, vertices, 0,
                            vertices.Length, indices, 0, (int) pcmd->ElemCount / 3);
                    }
                    idxBuffer += pcmd->ElemCount;
                }
            }
        }

        public void Dispose()
        {
            _rasterizerState.Dispose();
            _spriteEffect.Dispose();
        }
    }
}

MemoryEditor.cs

using System;
using System.Globalization;

namespace ImGuiNET
{
    // C# port of ocornut's imgui_memory_editor.h - https://gist.github.com/ocornut/0673e37e54aff644298b

    // Mini memory editor for ImGui (to embed in your game/tools)
    // v0.10
    // Animated gif: https://cloud.githubusercontent.com/assets/8225057/9028162/3047ef88-392c-11e5-8270-a54f8354b208.gif
    //
    // You can adjust the keyboard repeat delay/rate in ImGuiIO.
    // The code assume a mono-space font for simplicity! If you don't use the default font, use ImGui::PushFont()/PopFont() to switch to a mono-space font before caling this.
    //
    // Usage:
    //   static MemoryEditor memory_editor;                                                     // save your state somewhere
    //   memory_editor.Draw("Memory Editor", mem_block, mem_block_size, (size_t)mem_block);     // run

    public class MemoryEditor
    {
        readonly bool _allowEdits;
        int _rows;
        int _dataEditingAddr;
        bool _dataEditingTakeFocus;
        readonly byte[] _dataInput = new byte[32];
        readonly byte[] _addrInput = new byte[32];

        public MemoryEditor()
        {
            _rows = 16;
            _dataEditingAddr = -1;
            _dataEditingTakeFocus = false;
            _allowEdits = true;
        }

        private static string FixedHex(int v, int count)
        {
            return v.ToString("X").PadLeft(count, '0');
        }

        private static bool TryHexParse(byte[] bytes, out int result)
        {
            string input = System.Text.Encoding.UTF8.GetString(bytes).ToString();
            return int.TryParse(input, NumberStyles.AllowHexSpecifier, CultureInfo.CurrentCulture, out result);
        }

        private static void ReplaceChars(byte[] bytes, string input)
        {
            var address = System.Text.Encoding.ASCII.GetBytes(input);
            for (int i = 0; i < bytes.Length; i++)
            {
                bytes[i] = (i < address.Length) ? address[i] : (byte)0;
            }
        }

        public unsafe void Draw(string title, byte[] memData, int memSize, int baseDisplayAddr = 0)
        {
            if (!ImGui.BeginWindow(title))
            {
                ImGui.EndWindow();
                return;
            }

            float lineHeight = ImGuiNative.igGetTextLineHeight();
            int lineTotalCount = (memSize + _rows - 1) / _rows;

            ImGuiNative.igSetNextWindowContentSize(new Vector2(0.0f, lineTotalCount * lineHeight));
            ImGui.BeginChild("##scrolling", new Vector2(0, -ImGuiNative.igGetItemsLineHeightWithSpacing()), false, 0);

            ImGui.PushStyleVar(StyleVar.FramePadding, new Vector2(0, 0));
            ImGui.PushStyleVar(StyleVar.ItemSpacing, new Vector2(0, 0));

            int addrDigitsCount = 0;
            for (int n = baseDisplayAddr + memSize - 1; n > 0; n >>= 4)
                addrDigitsCount++;

            float glyphWidth = ImGui.GetTextSize("F").X;
            float cellWidth = glyphWidth * 3; // "FF " we include trailing space in the width to easily catch clicks everywhere

            var clipper = new ImGuiListClipper(lineTotalCount, lineHeight);
            int visibleStartAddr = clipper.DisplayStart * _rows;
            int visibleEndAddr = clipper.DisplayEnd * _rows;

            bool dataNext = false;

            if (!_allowEdits || _dataEditingAddr >= memSize)
                _dataEditingAddr = -1;

            int dataEditingAddrBackup = _dataEditingAddr;

            if (_dataEditingAddr != -1)
            {
                if (ImGui.IsKeyPressed(ImGui.GetKeyIndex(GuiKey.UpArrow)) && _dataEditingAddr >= _rows) { _dataEditingAddr -= _rows; _dataEditingTakeFocus = true; }
                else if (ImGui.IsKeyPressed(ImGui.GetKeyIndex(GuiKey.DownArrow)) && _dataEditingAddr < memSize - _rows) { _dataEditingAddr += _rows; _dataEditingTakeFocus = true; }
                else if (ImGui.IsKeyPressed(ImGui.GetKeyIndex(GuiKey.LeftArrow)) && _dataEditingAddr > 0) { _dataEditingAddr -= 1; _dataEditingTakeFocus = true; }
                else if (ImGui.IsKeyPressed(ImGui.GetKeyIndex(GuiKey.RightArrow)) && _dataEditingAddr < memSize - 1) { _dataEditingAddr += 1; _dataEditingTakeFocus = true; }
            }
            if ((_dataEditingAddr / _rows) != (dataEditingAddrBackup / _rows))
            {
                // Track cursor movements
                float scrollOffset = ((_dataEditingAddr / _rows) - (dataEditingAddrBackup / _rows)) * lineHeight;
                bool scrollDesired = (scrollOffset < 0.0f && _dataEditingAddr < visibleStartAddr + _rows * 2) || (scrollOffset > 0.0f && _dataEditingAddr > visibleEndAddr - _rows * 2);
                if (scrollDesired)
                    ImGuiNative.igSetScrollY(ImGuiNative.igGetScrollY() + scrollOffset);
            }

            for (int lineI = clipper.DisplayStart; lineI < clipper.DisplayEnd; lineI++) // display only visible items
            {
                int addr = lineI * _rows;
                ImGui.Text(FixedHex(baseDisplayAddr + addr, addrDigitsCount) + ": ");
                ImGui.SameLine();

                // Draw Hexadecimal
                float lineStartX = ImGuiNative.igGetCursorPosX();
                for (int n = 0; n < _rows && addr < memSize; n++, addr++)
                {
                    ImGui.SameLine(lineStartX + cellWidth * n);

                    if (_dataEditingAddr == addr)
                    {
                        // Display text input on current byte
                        ImGui.PushID(addr);

                        // FIXME: We should have a way to retrieve the text edit cursor position more easily in the API, this is rather tedious.
                        TextEditCallback callback = (data) =>
                        {
                            int* pCursorPos = (int*)data->UserData;
                            if (!data->HasSelection())
                                *pCursorPos = data->CursorPos;
                            return 0;
                        };
                        int cursorPos = -1;
                        bool dataWrite = false;
                        if (_dataEditingTakeFocus)
                        {
                            ImGui.SetKeyboardFocusHere();
                            ReplaceChars(_dataInput, FixedHex(memData[addr], 2));
                            ReplaceChars(_addrInput, FixedHex(baseDisplayAddr + addr, addrDigitsCount));
                        }
                        ImGui.PushItemWidth(ImGui.GetTextSize("FF").X);

                        var flags = InputTextFlags.CharsHexadecimal | InputTextFlags.EnterReturnsTrue | InputTextFlags.AutoSelectAll | InputTextFlags.NoHorizontalScroll | InputTextFlags.AlwaysInsertMode | InputTextFlags.CallbackAlways;
                        if (ImGui.InputText("##data", _dataInput, 32, flags, callback, new IntPtr(&cursorPos)))
                            dataWrite = dataNext = true;
                        else if (!_dataEditingTakeFocus && !ImGui.IsLastItemActive())
                            _dataEditingAddr = -1;

                        _dataEditingTakeFocus = false;
                        ImGui.PopItemWidth();
                        if (cursorPos >= 2)
                            dataWrite = dataNext = true;
                        if (dataWrite)
                        {
                            int data;
                            if (TryHexParse(_dataInput, out data))
                                 memData[addr] = (byte)data;
                        }
                        ImGui.PopID();
                    }
                    else
                    {
                        ImGui.Text(FixedHex(memData[addr], 2));
                        if (_allowEdits && ImGui.IsLastItemHovered() && ImGui.IsMouseClicked(0))
                        {
                            _dataEditingTakeFocus = true;
                            _dataEditingAddr = addr;
                        }
                    }
                }

                ImGui.SameLine(lineStartX + cellWidth * _rows + glyphWidth * 2);
                //separator line drawing replaced by printing a pipe char

                // Draw ASCII values
                addr = lineI * _rows;
                var asciiVal = new System.Text.StringBuilder(2 + _rows);
                asciiVal.Append("| ");
                for (int n = 0; n < _rows && addr < memSize; n++, addr++)
                {
                    int c = memData[addr];
                    asciiVal.Append((c >= 32 && c < 128) ? Convert.ToChar(c) : '.');
                }
                ImGui.TextUnformatted(asciiVal.ToString());  //use unformatted, so string can contain the '%' character
            }
            //clipper.End();  //not implemented
            ImGui.PopStyleVar(2);

            ImGui.EndChild();

            if (dataNext && _dataEditingAddr < memSize)
            {
                _dataEditingAddr = _dataEditingAddr + 1;
                _dataEditingTakeFocus = true;
            }

            ImGui.Separator();
                
            ImGuiNative.igAlignFirstTextHeightToWidgets();
            ImGui.PushItemWidth(50);
            ImGuiNative.igPushAllowKeyboardFocus(false);
            int rowsBackup = _rows;
            if (ImGui.DragInt("##rows", ref _rows, 0.2f, 4, 32, "%.0f rows"))
            {
                if (_rows <= 0) _rows = 4;
                Vector2 newWindowSize = ImGui.GetWindowSize();
                newWindowSize.X += (_rows - rowsBackup) * (cellWidth + glyphWidth);
                ImGui.SetWindowSize(newWindowSize);
            }
            ImGuiNative.igPopAllowKeyboardFocus();
            ImGui.PopItemWidth();
            ImGui.SameLine();
            ImGui.Text(string.Format(" Range {0}..{1} ", FixedHex(baseDisplayAddr, addrDigitsCount), 
                FixedHex(baseDisplayAddr + memSize - 1, addrDigitsCount)));
            ImGui.SameLine();
            ImGui.PushItemWidth(70);
            if (ImGui.InputText("##addr", _addrInput, 32, InputTextFlags.CharsHexadecimal | InputTextFlags.EnterReturnsTrue, null))
            {
                int gotoAddr;
                if (TryHexParse(_addrInput, out gotoAddr))
                {
                    gotoAddr -= baseDisplayAddr;
                    if (gotoAddr >= 0 && gotoAddr < memSize)
                    {
                        ImGui.BeginChild("##scrolling");
                        ImGuiNative.igSetScrollFromPosY(ImGui.GetCursorStartPos().Y + (gotoAddr / _rows) * ImGuiNative.igGetTextLineHeight());
                        ImGui.EndChild();
                        _dataEditingAddr = gotoAddr;
                        _dataEditingTakeFocus = true;
                    }
                }
            }
            ImGui.PopItemWidth();
            
            ImGui.EndWindow();
        }
    }

    //Not a proper translation, because ImGuiListClipper uses imgui's internal api.
    //Thus SetCursorPosYAndSetupDummyPrevLine isn't reimplemented, but SetCursorPosY + SetNextWindowContentSize seems to be working well instead.
    //TODO expose clipper through newer cimgui version
    internal class ImGuiListClipper
    {
        public float StartPosY;
        public float ItemsHeight;
        public int ItemsCount, StepNo, DisplayStart, DisplayEnd;

        public ImGuiListClipper(int itemsCount = -1, float itemsHeight = -1.0f)
        {
            Begin(itemsCount, itemsHeight);
        }

        public void Begin(int count, float itemsHeight = -1.0f)
        {
            StartPosY = ImGuiNative.igGetCursorPosY();
            ItemsHeight = itemsHeight;
            ItemsCount = count;
            StepNo = 0;
            DisplayEnd = DisplayStart = -1;
            if (ItemsHeight > 0.0f)
            {
                ImGui.CalcListClipping(ItemsCount, ItemsHeight, ref DisplayStart, ref DisplayEnd); // calculate how many to clip/display
                if (DisplayStart > 0)
                    //SetCursorPosYAndSetupDummyPrevLine(StartPosY + DisplayStart * ItemsHeight, ItemsHeight); // advance cursor
                    ImGuiNative.igSetCursorPosY(StartPosY + DisplayStart * ItemsHeight);
                StepNo = 2;
            }
        }
    }
}

Thanks for this!
I forked and updated this to the latest imgui.net nuget package (0.47), btw.