从C ++ COM DLL回调到C＃应用程序 [英] Callback from a C++ COM DLL to a C# application

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问题描述

这将是一个长的职位，因为我想暴露你所有的步骤，我试图使这项工作：）



我有C + + COM dll包含使用Media Foundation API显示视频的VideoPlayer类。



VideoPlayer类使用IDL文件定义：

  [
 object，
 uuid（74FDBBB1-BFFB-4F7E-ACA3-ADB0C7232790），
 dual，
不可扩展， 
 pointer_default（unique）
] 
 interface IVideoPlayer：IDispatch {
 
 [id（1）] HRESULT初始化（[in] HWND * video_hwnd，[in] HWND * event_hwnd）; 
 [id（2）] HRESULT OpenUrl（[in] BSTR url_path）; 
 [id（3）] HRESULT Play（）; 
 [id（4）] HRESULT HandleEvent（[in] INT pEventPtr）; 
 [id（5）] HRESULT重绘（void）; 
 [id（6）] HRESULT调整大小（[in] LONG宽度，[in] LONG高度）; 
};

这个类在内部使用自定义的Presenter（基于 WPFMediaKit 项目），它输出IDirect3DSurface9对象内的视频帧。



需要一个IEVRPresenterCallback类型的回调，定义如下：

  MIDL_INTERFACE（B92D8991-6C42-4e51-B942-E61CB8696FCB ）
 IEVRPresenterCallback：public IUnknown 
 {
 public：
 virtual HRESULT STDMETHODCALLTYPE PresentSurfaceCB（IDirect3DSurface9 * pSurface）= 0; 
};

正如你所看到的，它没有在IDL文件中定义， 。



我需要向VideoPlayer类添加一个新函数，它允许调用C＃代码传递从IEVRPresenterCallback继承的类的实例，该类将被设置为



我已尝试将此行添加到VideoPlayer的IDL文件：

  [id（7）] HRESULT RegisterCallback2（[in] IEVRPresenterCallback * p_PresenterCallback）;

但我收到一个错误：


错误MIDL2025：语法错误：期望接近
的类型规范IEVRPresenterCallback


这是正常的，因为我没有在IDL中导入任何东西。这是正常的，因为IEVRPresenterCallback在头文件中定义。



我试图导入头文件，但IEVRPresenterCallback定义的MIDL_INTERFACE宏生成错误： p>

/ b 错误MIDL2025：语法错误：期望接口名称或DispatchInterfaceName或CoclassName或ModuleName或LibraryName或ContractName或类型规范MIDL_INTERFACE p>

然后我尝试转发声明接口，但我收到此错误：


错误MIDL2011：未解析的类型声明：IEVRPresenterCallback [Procedure'RegisterCallback2'（Interface'IVideoPlayer'）的参数'p_PresenterCallback']


我最后一次尝试是改变RegisterCallback的定义，有一个指向IUnknown而不是IEVRPresenterCallback的指针，在函数的声明中，我将指针转换到正确的接口。



这使得C ++ dll编译正确。



在C＃应用程序中，我设置回调如下：

  [ComVisible（true），ComImport，SuppressUnmanagedCodeSecurity，Guid（B92D8991-6C42-4e51-B942-E61CB8696FCB），InterfaceType（ComInterfaceType.InterfaceIsIUnknown）] 
内部接口IEVRPresenterCallback 
 {
 [ PreserveSig] 
 int PresentSurfaceCB（IntPtr pSurface）; 
} 
 
内部类EVRPresenterCallback：IEVRPresenterCallback 
 {
 public int PresentSurfaceCB（IntPtr pSurface）
 {
 return 0; 
} 
} 
 
 public partial class MainWindow：Window 
 {
 private EmideeMediaFoundationLib.IVideoPlayer videoPlayer = new EmideeMediaFoundationLib.VideoPlayer（）; 
 private EVRPresenterCallback callback = new EVRPresenterCallback（）; 
 
 public MainWindow（）
 {
 InitializeComponent（）; 
} 
 
 private void Button_Click（object sender，RoutedEventArgs e）
 {
 videoHost.VideoPlayer.RegisterCallback（callback）; 
 videoHost.VideoPlayer.OpenUrl（@C：\Users\Public\Videos\Sample Videos\wildlife.wmv）; 
} 
}

我得到的问题是尽管自定义演示者调用回调，我从来没有回到C＃PresentSurfaceCB函数。



我现在完全陷入困境，我不知道问题在哪里，也不知道如何解决



提前感谢



我已经在IDL文件中移动了接口，而改为在回调中返回一个ID3D9Surface指针，我返回一个DOWRD_PTR：

  [
 uuid（B92D8991-6C42-4e51 B742-E61CB8696FCB），
] 
接口IEVRPresenterCallback：IUnknown {
 [id（1）] HRESULT PresentSurfaceCB（DWORD_PTR pSurface）; 
} 
 
 [
 object，
 uuid（74FDBBB1-BFFB-4F7E-ACA3-ADB0C7232790），
 dual，
 nonextensible，
 pointer_default（unique）
] 
 interface IVideoPlayer：IDispatch {
 
 [id（1）] HRESULT初始化（[in] HWND * video_hwnd，[in] HWND * event_hwnd）; 
 [id（2）] HRESULT OpenUrl（[in] BSTR url_path）; 
 [id（3）] HRESULT Play（）; 
 [id（4）] HRESULT HandleEvent（[in] INT pEventPtr）; 
 [id（5）] HRESULT重绘（void）; 
 [id（6）] HRESULT调整大小（[in] LONG宽度，[in] LONG高度）; 
 [id（7）] HRESULT RegisterCallback（[in] IEVRPresenterCallback * p_PresenterCallback）; 
};



在我的WPF应用程序中，我创建一个从IEVRCallback派生的类：

 内部类EVRPresenterCallback：EmideeMediaFoundationLib.IEVRPresenterCallback 
 {
 public void PresentSurfaceCB（uint pSurface）
 {
} 
}

我将此实例赋予VideoPlayer对象。


This is going to be a long post, as I want to expose you all the steps I tried to make this work :)

I have C++ COM dll which contains a VideoPlayer class which uses the Media Foundation API to display a video.

The VideoPlayer class is defined using an IDL file:

[
    object,
    uuid(74FDBBB1-BFFB-4F7E-ACA3-ADB0C7232790),
    dual,
    nonextensible,
    pointer_default(unique)
]
interface IVideoPlayer : IDispatch {

    [id(1)] HRESULT Initialize([in] HWND* video_hwnd, [in] HWND* event_hwnd);
    [id(2)] HRESULT OpenUrl([in] BSTR url_path);
    [id(3)] HRESULT Play();
    [id(4)] HRESULT HandleEvent([in] INT pEventPtr);
    [id(5)] HRESULT Repaint(void);
    [id(6)] HRESULT Resize([in] LONG width, [in] LONG height);
};

This class internally uses a custom presenter (which is based on the WPFMediaKit project), which outputs the video frames inside a IDirect3DSurface9 object.

The custom presenter needs a callback of type IEVRPresenterCallback, which is defined as follow:

MIDL_INTERFACE("B92D8991-6C42-4e51-B942-E61CB8696FCB")
IEVRPresenterCallback : public IUnknown
{
public:
    virtual HRESULT STDMETHODCALLTYPE PresentSurfaceCB(IDirect3DSurface9 *pSurface) = 0;
};

As you can see, it is not defined in a IDL file, but is declared in a header file.

I need to add a new function to the VideoPlayer class, which allows the calling C# code to pass an instance of a class inheriting from IEVRPresenterCallback, which will be set to the custom presenter.

I've tried to add this line to the IDL file of the VideoPlayer:

[id(7)] HRESULT RegisterCallback2([in] IEVRPresenterCallback * p_PresenterCallback);

But I get an error:

error MIDL2025: syntax error : expecting a type specification near "IEVRPresenterCallback"

I guess it is normal, because I didn't import anything in the IDL. Which is normal, as IEVRPresenterCallback is defined in a header file.

I tried to import the header file, but the MIDL_INTERFACE macro of the IEVRPresenterCallback definition generates an error:

error MIDL2025: syntax error : expecting an interface name or DispatchInterfaceName or CoclassName or ModuleName or LibraryName or ContractName or a type specification near "MIDL_INTERFACE"

I then tried to forward declare the interface, but I got this error:

error MIDL2011: unresolved type declaration : IEVRPresenterCallback [ Parameter 'p_PresenterCallback' of Procedure 'RegisterCallback2' ( Interface 'IVideoPlayer' ) ]

My last attempt was to change the definition of RegisterCallback, to have a pointer to IUnknown instead of IEVRPresenterCallback, and in the declaration of the function, I cast the pointer to the correct interface.

This makes the C++ dll compile correctly.

In the C# application, I set the callback as follow:

[ComVisible(true), ComImport, SuppressUnmanagedCodeSecurity, Guid("B92D8991-6C42-4e51-B942-E61CB8696FCB"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
internal interface IEVRPresenterCallback
{
    [PreserveSig]
    int PresentSurfaceCB(IntPtr pSurface);
}

internal class EVRPresenterCallback : IEVRPresenterCallback
{
    public int PresentSurfaceCB(IntPtr pSurface)
    {
        return 0;
    }
}

public partial class MainWindow : Window
{
    private EmideeMediaFoundationLib.IVideoPlayer videoPlayer = new EmideeMediaFoundationLib.VideoPlayer();
    private EVRPresenterCallback callback = new EVRPresenterCallback();

    public MainWindow()
    {
        InitializeComponent();
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        videoHost.VideoPlayer.RegisterCallback(callback);
        videoHost.VideoPlayer.OpenUrl(@"C:\Users\Public\Videos\Sample Videos\wildlife.wmv");
    }
}

The problem I get is despite the custom presenter calling the callback, I never get back in the C# PresentSurfaceCB function.

I'm completely stuck right now, and I don't know where the problem is, nor how to solve it :(

Any ideas?

Thanks in advance

解决方案

Thanks to Hans, I could make it work.

I moved the interface in the IDL file, and instead of returning a ID3D9Surface pointer in the callback, I return a DOWRD_PTR:

[
    uuid(B92D8991-6C42-4e51-B942-E61CB8696FCB),
]
interface IEVRPresenterCallback : IUnknown {
    [id(1)] HRESULT PresentSurfaceCB( DWORD_PTR pSurface);
}

[
    object,
    uuid(74FDBBB1-BFFB-4F7E-ACA3-ADB0C7232790),
    dual,
    nonextensible,
    pointer_default(unique)
]
interface IVideoPlayer : IDispatch {

    [id(1)] HRESULT Initialize([in] HWND* video_hwnd, [in] HWND* event_hwnd);
    [id(2)] HRESULT OpenUrl([in] BSTR url_path);
    [id(3)] HRESULT Play();
    [id(4)] HRESULT HandleEvent([in] INT pEventPtr);
    [id(5)] HRESULT Repaint(void);
    [id(6)] HRESULT Resize([in] LONG width, [in] LONG height);
    [id(7)] HRESULT RegisterCallback([in] IEVRPresenterCallback * p_PresenterCallback);
};

In my WPF application, I create a class deriving from IEVRCallback:

internal class EVRPresenterCallback : EmideeMediaFoundationLib.IEVRPresenterCallback
{
    public void PresentSurfaceCB(uint pSurface)
    {
    }
}

and I give this instance to the VideoPlayer object.

这篇关于从C ++ COM DLL回调到C＃应用程序的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

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