ImGui window with splitter using docking

example.cs

using System;

public abstract class SplitWindow
{
    private string _leftTitle;
    private string _rightTitle;
    private string _dockSpaceId;
    private Action _drawLeft;
    private Action _drawRight;
    public string Title;
    private readonly Action<uint> _initializeDockSpace;

    protected SplitWindow(string title)
    {
        _leftTitle = $"{title}_Left";
        _rightTitle = $"{title}_Right";
        _dockSpaceId = $"{title}_DockSpace";

        _drawLeft = DrawLeft;
        _drawRight = DrawRight;
        _initializeDockSpace = InitializeDockSpace(_leftTitle, _rightTitle);
    }

    public void Draw(ref bool isOpen)
    {
        if (!isOpen)
            return;

        CreateDockSpace(Title, _dockSpaceId, ref isOpen, _initializeDockSpace);

        DrawSplit(_leftTitle, _drawLeft);
        DrawSplit(_rightTitle, _drawRight);
    }

    private static void CreateDockSpace(string windowTitle, string dockspaceId, ref bool isOpen, Action<uint> initializeLayout,
        ImGuiWindowFlags flags = ImGuiWindowFlags.NoCollapse)
    {
        ImGui.SetNextWindowSize(new Vector2(800, 850), ImGuiCond.Appearing);
        ImGui.SetNextWindowSizeConstraints(new Vector2(200, 200), new Vector2(800, 850));
        var result = ImGui.Begin(windowTitle, ImGuiExt.RefPtr(ref isOpen), flags);
        SetupDockSpace(dockspaceId, initializeLayout, !result);
        ImGui.End();
    }

    private static Action<uint> InitializeDockSpace(string leftWindowTitle, string rightWindowTitle)
    {
        return dockspaceID =>
        {
            var rightDockID = 0u;
            var leftDockID = 0u;
            ImGuiInternal.DockBuilderSplitNode(dockspaceID, ImGuiDir.Left, 0.5f, &leftDockID, &rightDockID);
            ImGuiInternal.DockBuilderDockWindow(leftWindowTitle, leftDockID);
            ImGuiInternal.DockBuilderDockWindow(rightWindowTitle, rightDockID);
        };
    }

    private static void DrawSplit(string title, Action drawContent)
    {
        if (ImGui.Begin(title))
        {
            drawContent();
        }

        SetDockSpaceFlags();
        ImGui.End();
    }

    private static void SetDockSpaceFlags()
    {
        var dockNode = ImGuiInternal.GetWindowDockNode();
        if (dockNode != null)
        {
            dockNode->LocalFlags = 0;
            dockNode->LocalFlags |= (ImGuiDockNodeFlags)(ImGuiDockNodeFlagsPrivate_.ImGuiDockNodeFlags_NoDockingSplitMe);
            dockNode->LocalFlags |= (ImGuiDockNodeFlags)(ImGuiDockNodeFlagsPrivate_.ImGuiDockNodeFlags_NoDockingOverMe);
            dockNode->LocalFlags |= (ImGuiDockNodeFlags)(ImGuiDockNodeFlagsPrivate_.ImGuiDockNodeFlags_NoTabBar);
        }
    }

    protected abstract void DrawLeft();
    protected abstract void DrawRight();
    
    private static void SetupDockSpace(string dockspaceId, Action<uint> setupCallback, bool keepAlive = false)
    {
        var dockspaceID = ImGui.GetID(dockspaceId);

        ImGuiWindowClass workspaceWindowClass;
        workspaceWindowClass.ClassId = dockspaceID;
        workspaceWindowClass.DockingAllowUnclassed = false;

        if (ImGuiInternal.DockBuilderGetNode(dockspaceID) == null)
        {
            var dockFlags = ImGuiDockNodeFlagsPrivate_.ImGuiDockNodeFlags_DockSpace |
                            ImGuiDockNodeFlagsPrivate_.ImGuiDockNodeFlags_NoWindowMenuButton |
                            ImGuiDockNodeFlagsPrivate_.ImGuiDockNodeFlags_NoCloseButton;
            ImGuiInternal.DockBuilderAddNode(dockspaceID, (ImGuiDockNodeFlags)dockFlags);
            var contentAvail = ImGui.GetContentRegionAvail();
            var size = new Num.Vector2(MathF.Max(4.0f, contentAvail.X), MathF.Max(4.0f, contentAvail.Y));
            ImGuiInternal.DockBuilderSetNodeSize(dockspaceID, size);
            //
            setupCallback.Invoke(dockspaceID);
            //
            ImGuiInternal.DockBuilderFinish(dockspaceID);
        }

        var flags = keepAlive ? ImGuiDockNodeFlags.KeepAliveOnly : ImGuiDockNodeFlags.None | ImGuiDockNodeFlags.NoSplit;
        ImGui.DockSpace(dockspaceID, new Num.Vector2(0.0f, 0.0f), flags, &workspaceWindowClass);
    }
}