Imgui Docking feature "undocks" previously docked windows

[OneAbowAll]

Summary

For some reason when closing and reopening the app Imgui undocks all the windows that were docked.

Steps to reproduce

• Platform: Desktop
• Framework Version: .NET Core 3, .NET 8
• API: OpenGL
• API Version: OpenGL 4.6 Core

1. Dock windows anyway you like
2. Close app
3. Reopen app

Comments

Right now this is the flags that I'm setting OnLoad:

    io.ConfigFlags |= ImGuiConfigFlags.DockingEnable;

And this is the code im using to create the Dockspace / OnRender code:

Gl.Clear((uint) ClearBufferMask.ColorBufferBit);
controller.Update((float)delta);
ImGui.DockSpaceOverViewport(ImGui.GetMainViewport(), ImGuiDockNodeFlags.PassthruCentralNode);

ImGui.BeginDemoWindow();
//etc... etc...
controller.Render();

Example Image

Before closing the app:

After closing and then reopening the app:

As you can see the window's positions are correct, but the expected behaviour is not.

[OneAbowAll]

Ok after looking into it i think i found a solution.
You have to set the DockingEnable config flag as soon as possible inside the constructor of ImGuiController.

public ImGuiController(GL gl, IView view, IInputContext input, ImGuiFontConfig? imGuiFontConfig = null, Action onConfigureIO = null)
{
    Init(gl, view, input);
    ImGuiIOPtr iO = ImGuiNET.ImGui.GetIO();
    if (imGuiFontConfig.HasValue)
    {
        IntPtr glyph_ranges = imGuiFontConfig.Value.GetGlyphRange?.Invoke(iO) ?? ((IntPtr)0);
        iO.Fonts.AddFontFromFileTTF(imGuiFontConfig.Value.FontPath, imGuiFontConfig.Value.FontSize, null, glyph_ranges);
    }

    onConfigureIO?.Invoke();
    iO.BackendFlags |= ImGuiBackendFlags.RendererHasVtxOffset;

    iO.ConfigFlags |= ImGuiConfigFlags.DockingEnable;

    CreateDeviceResources();
    SetKeyMappings();
    SetPerFrameImGuiData(1f / 60f);
    BeginFrame();
}

I think the problem might be that BeginFrame is called inside the constructor, meaning that any user-specified flag outside the constructor are not considered when drawing the interface for the first time, but its just an educated guess.

[Perksey]

I’m glad you found a solution! Note that these sorts of things is why we expose the onConfigureIO callback, so hopefully this helps and you don’t need to manually edit the controller source :)