Request: Add support for ImPlot3D add-on via cimgui binding

[nikmanderss]

What

Requesting an add-on binding for ImPlot3D, a 3D plotting extension built for ImPlot. You can view an online demo here.

How

Per convo with Juna:

• cimgui-style bindings already exist via cimplot3d.
• The generator isn’t limited to ImGui specifically and handles most C libraries well.

[JunaMeinhold]

Hi, check out the latest pre-release version, i added support for ImPlot3D in it, if there are any issues with the wrapper please post them here.

[nikmanderss]

Sounds good, I'll give this a try within a couple days or so.

Thanks in advance!

[nikmanderss]

Summary

Trying to validate the new ImPlot3D wrapper by showing the demo window in the GLFW + D3D11 example. I create ImGui + ImPlot + ImPlot3D contexts, but the app crashes in native code on the first ImPlot/ImPlot3D demo call. I’m an experienced C# developer, but relatively new to native interop/wrappers—apologies if I’m missing something obvious. I wanted to share the minimal of what I tried below.

Minimal code (Program.cs)

// contexts
var guiContext = ImGui.CreateContext();
ImGui.SetCurrentContext(guiContext);

var implotCtx = ImPlot.CreateContext();
var implot3Ctx = ImPlot3D.CreateContext();

----------

// inside Main loop
ImGuiImplD3D11.NewFrame();
ImGuiImplGLFW.NewFrame();
ImGui.NewFrame();

ImGui.ShowDemoWindow();

// tried both forms for each demo:
ImPlot.ShowDemoWindow();
ImPlot3D.ShowDemoWindow();

ImGui.Render();
manager.SetTarget();
ImGuiImplD3D11.RenderDrawData(ImGui.GetDrawData());

// shutdown
ImPlot3D.DestroyContext(implot3dContext );
ImPlot.DestroyContext(implot2dContext );
ImGui.DestroyContext(guiContext );

What happens

• Immediate native crash on the first ImPlot/ImPlot3D demo call:

Exception thrown at 0x00007FF827007A17 (cimplot.dll/cimplot3d.dll) ) in ExampleGLFWD3D11.exe: 0xC0000005: Access violation reading location 0x0000000000001580.

• Both ImPlot.GetCurrentContext() and ImPlot3D.GetCurrentContext() are non-zero before the call.

[JunaMeinhold]

You forgot to do those calls, those must be done before you call anything else

ImPlot3D.SetImGuiContext(imguiContext);
ImPlot.SetImGuiContext(imguiContext);

[nikmanderss]

Perhaps I didn't because ImPlot3D did not have SetImGuiContext available.
The generated Functions.000.cs only have the following Set methods:

		[NativeName(NativeNameType.Func, "ImPlot3D_SetCurrentContext")]
		[return: NativeName(NativeNameType.Type, "void")]
		[MethodImpl(MethodImplOptions.AggressiveInlining)]
		internal static void SetCurrentContextNative([NativeName(NativeNameType.Param, "ctx")] [NativeName(NativeNameType.Type, "ImPlot3DContext*")] ImPlot3DContext* ctx)
		{
			#if NET5_0_OR_GREATER
			((delegate* unmanaged[Cdecl]<ImPlot3DContext*, void>)funcTable[3])(ctx);
			#else
			((delegate* unmanaged[Cdecl]<nint, void>)funcTable[3])((nint)ctx);
			#endif
		}

		[NativeName(NativeNameType.Func, "ImPlot3D_SetCurrentContext")]
		[return: NativeName(NativeNameType.Type, "void")]
		public static void SetCurrentContext([NativeName(NativeNameType.Param, "ctx")] [NativeName(NativeNameType.Type, "ImPlot3DContext*")] ImPlot3DContextPtr ctx)
		{
			SetCurrentContextNative(ctx);
		}

		[NativeName(NativeNameType.Func, "ImPlot3D_SetCurrentContext")]
		[return: NativeName(NativeNameType.Type, "void")]
		public static void SetCurrentContext([NativeName(NativeNameType.Param, "ctx")] [NativeName(NativeNameType.Type, "ImPlot3DContext*")] ref ImPlot3DContext ctx)
		{
			fixed (ImPlot3DContext* pctx = &ctx)
			{
				SetCurrentContextNative((ImPlot3DContext*)pctx);
			}
		}

Simply using the SetCurrentContext results in similar error

Exception thrown at 0x00007FF90D329B88 (cimplot3d.dll) in ExampleGLFWD3D11.exe: 0xC0000005: Access violation writing location 0x0000000000001FB0.

[JunaMeinhold]

Yeah, cimplot3d didn't specify it correctly... I will fix that later

[JunaMeinhold]

Update: I published a patch for the missing function, should be available right away on nuget.

[nikmanderss]

No luck yet, infamous error again:

Exception thrown at 0x00007FF84F8F1D0C (cimplot3d.dll) in ExampleGLFWD3D11.exe: 0xC0000005: Access violation reading location 0x0000000000000000.

Below is the minimal changes I am working with. Any demo windows called from the ImPlot3D project will fail in their respective internal static void Show method

[JunaMeinhold]

Maybe try setting the allocator callbacks to prevent dll boundary issues

[nikmanderss]

You may have to be more specific. Found a reference to build off from in your Discord chat to start with:

I am assuming this what you meant, so I added the following to call before var guiContext = ImGui.CreateContext();

using Hexa.NET.ImGui;
using System.Runtime.InteropServices;

namespace ExampleGLFWD3D11;

public static class ImGuiAlloc
{
    private static ImGuiMemAllocFunc? _allocDel;
    private static ImGuiMemFreeFunc? _freeDel;

    /// <summary>
    /// Must be set before you create the ImGuiContext.
    /// This could fix many issues with cross dll memory boundary issues.
    /// </summary>
    public static unsafe void Set()
    {
        _allocDel = Alloc;
        _freeDel = Free;

        ImGui.SetAllocatorFunctions(_allocDel, _freeDel);
    }

    private static unsafe void Free(void* ptr, void* userData)
    {
        NativeMemory.Free(ptr);
    }

    private static unsafe void* Alloc(nuint size, void* userData)
    {
        return NativeMemory.Alloc(size);
    }
}

Usage:

ImGuiAlloc.Set(); 

var guiContext = ImGui.CreateContext();
ImGui.SetCurrentContext(guiContext);
ImPlot.SetImGuiContext(guiContext);
ImPlot3D.SetImGuiContext(guiContext);

Same result

Exception thrown at 0x00007FF909A51D0C (cimplot3d.dll) in ExampleGLFWD3D11.exe: 0xC0000005: Access violation reading location 0x0000000000000000.

[JunaMeinhold]

you have to set those for all addons too

[nikmanderss]

Good catch. However, I am not seeing a generated SetAllocatorFunctions under the ImPlot3D library.

[nikmanderss]

I haven't dug into this - as I have been away - but by chance, have you taken a stab at it? I see a new issue created #90 is this related?

[JunaMeinhold]

Maybe, do you have a ARM CPU?