Referencing C# GUI-Classes in C++

Durpler · January 3, 2021, 6:15pm

Hi there,
I’m currently trying to get into scripting for Flax and started by converting the current C# Samples to C++.
However I’ve already reached the first blocker for myself, since I’m not quite sure on how to reference the C# Classes for the UI.
I’ve noticed, that for a lot of components we have separate C++ - Header files, however for the UIComponents (Label e.g. ) I only found the C# implementations.

Do I need to use the managed-classes to reference the C# code in c++ or is there another way around that hurdle? Or would I even need to implement the C# classes in c++ by hand?

Would be really glad if someone could give me some pointers on how to achieve the reference.

Thank you

mafiesto4 · January 3, 2021, 7:02pm

UI in Flax is C#-only so it’s harder to use it in C++ but you can still access C# controls using C++ interop API we have via MClass/MField/MProperty/etc. Some info here: https://docs.flaxengine.com/manual/scripting/cpp/index.html#interop-with-c

Another example is UIControl Actor that contains C# control under the hood:

github.com

FlaxEngine/FlaxEngine/blob/master/Source/Engine/UI/UIControl.h

// Copyright (c) 2012-2020 Wojciech Figat. All rights reserved.

#pragma once

#include "Engine/Level/Actor.h"

/// <summary>
/// Contains a single GUI control (on C# side).
/// </summary>
API_CLASS(Sealed) class FLAXENGINE_API UIControl : public Actor
{
DECLARE_SCENE_OBJECT(UIControl);
public:

    // [Actor]
#if USE_EDITOR
    BoundingBox GetEditorBox() const override;
#endif
    void Serialize(SerializeStream& stream, const void* otherObj) override;
    void Deserialize(DeserializeStream& stream, ISerializeModifier* modifier) override;

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github.com

FlaxEngine/FlaxEngine/blob/master/Source/Engine/UI/UIControl.cpp

// Copyright (c) 2012-2020 Wojciech Figat. All rights reserved.

#include "UIControl.h"
#include "Engine/Scripting/MException.h"
#include "Engine/Scripting/ManagedCLR/MMethod.h"
#include "Engine/Scripting/ManagedCLR/MClass.h"
#include "Engine/Scripting/Scripting.h"
#include "Engine/Serialization/Serialization.h"
#include <ThirdParty/mono-2.0/mono/metadata/appdomain.h>

// Cached methods (FlaxEngine.CSharp.dll is loaded only once)
MMethod* UIControl_Serialize = nullptr;
MMethod* UIControl_SerializeDiff = nullptr;
MMethod* UIControl_Deserialize = nullptr;
MMethod* UIControl_ParentChanged = nullptr;
MMethod* UIControl_TransformChanged = nullptr;
MMethod* UIControl_OrderInParentChanged = nullptr;
MMethod* UIControl_ActiveInTreeChanged = nullptr;
MMethod* UIControl_BeginPlay = nullptr;
MMethod* UIControl_EndPlay = nullptr;

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github.com

FlaxEngine/FlaxEngine/blob/master/Source/Engine/UI/UIControl.cs

// Copyright (c) 2012-2020 Wojciech Figat. All rights reserved.

using System;
using System.Globalization;
using System.IO;
using System.Text;
using FlaxEngine.GUI;
using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;

namespace FlaxEngine
{
    partial class UIControl
    {
        private Control _control;

        /// <summary>
        /// Gets or sets the GUI control used by this actor.
        /// </summary>
        /// <remarks>

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