C# Com 与 Windows Media Player 可视化的互操作（带有示例代码）

Question

我正在尝试用 C# 创建 Windows Media Player (WMP) 可视化插件。我对将 C# 暴露给 COM 还很陌生，可能错过了一些基本的东西。我已经坚持了 3 天（大约 20 小时），但没有解决我将在下面描述的一个问题。

对于那些不知道的人来说，WMP 可视化是在听音乐时在媒体播放器中显示的漂亮图像。

简而言之：WMP 将调用我的 C# COM 接口上的某些方法，但不会调用其他方法。

我安装了 WMP 11

我下载了最新的 Windows SDK，其中包含用于编译工作可视化示例的 C++ 插件向导。该示例在 WMP 中注册并运行没有问题。

该开发工具包包含一个名为effects.h 的C++ 头文件，其中包含2 个接口，必须实现这些接口才能使插件与WMP 配合使用。看起来并没有比这更复杂的事情。

正如

MIDL_INTERFACE("D3984C13-C3CB-48e2-8BE5-5168340B4F35")
IWMPEffects : public IUnknown
{
public:
    virtual /* [helpstring][local] */ HRESULT STDMETHODCALLTYPE Render( 
        /* [in] */ TimedLevel *pLevels,
        /* [in] */ HDC hdc,
        /* [in] */ RECT *prc) = 0;

    virtual /* [helpstring] */ HRESULT STDMETHODCALLTYPE MediaInfo( 
        /* [in] */ LONG lChannelCount,
        /* [in] */ LONG lSampleRate,
        /* [in] */ BSTR bstrTitle) = 0;

    virtual /* [helpstring] */ HRESULT STDMETHODCALLTYPE GetCapabilities( 
        /* [out] */ DWORD *pdwCapabilities) = 0;

    virtual /* [helpstring] */ HRESULT STDMETHODCALLTYPE GetTitle( 
        /* [out] */ BSTR *bstrTitle) = 0;

    virtual /* [helpstring] */ HRESULT STDMETHODCALLTYPE GetPresetTitle( 
        /* [in] */ LONG nPreset,
        /* [out] */ BSTR *bstrPresetTitle) = 0;

    virtual /* [helpstring] */ HRESULT STDMETHODCALLTYPE GetPresetCount( 
        /* [out] */ LONG *pnPresetCount) = 0;

    virtual /* [helpstring] */ HRESULT STDMETHODCALLTYPE SetCurrentPreset( 
        /* [in] */ LONG nPreset) = 0;

    virtual /* [helpstring] */ HRESULT STDMETHODCALLTYPE GetCurrentPreset( 
        /* [out] */ LONG *pnPreset) = 0;

    virtual /* [helpstring] */ HRESULT STDMETHODCALLTYPE DisplayPropertyPage( 
        /* [in] */ HWND hwndOwner) = 0;

    virtual /* [helpstring] */ HRESULT STDMETHODCALLTYPE GoFullscreen( 
        /* [in] */ BOOL fFullScreen) = 0;

    virtual /* [helpstring] */ HRESULT STDMETHODCALLTYPE RenderFullScreen( 
        /* [in] */ TimedLevel *pLevels) = 0;

};

MIDL_INTERFACE("695386EC-AA3C-4618-A5E1-DD9A8B987632")
IWMPEffects2 : public IWMPEffects
{
public:
    virtual HRESULT STDMETHODCALLTYPE SetCore( 
        /* [in] */ IWMPCore *pPlayer) = 0;

    virtual HRESULT STDMETHODCALLTYPE Create( 
        /* [in] */ HWND hwndParent) = 0;

    virtual HRESULT STDMETHODCALLTYPE Destroy( void) = 0;

    virtual HRESULT STDMETHODCALLTYPE NotifyNewMedia( 
        /* [in] */ IWMPMedia *pMedia) = 0;

    virtual HRESULT STDMETHODCALLTYPE OnWindowMessage( 
        /* [in] */ UINT msg,
        /* [in] */ WPARAM WParam,
        /* [in] */ LPARAM LParam,
        /* [in] */ LRESULT *plResultParam) = 0;

    virtual HRESULT STDMETHODCALLTYPE RenderWindowed( 
        /* [in] */ TimedLevel *pData,
        /* [in] */ BOOL fRequiredRender) = 0;

};

我所提到的，我的 COM 知识并不是最好的。这就是我将其移植到 C# 所做的事情。

我将接口转换为以下

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;

namespace WmpTestPlugin
{

    [ComVisible(true)]
    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    [Guid("D3984C13-C3CB-48e2-8BE5-5168340B4F35")]
    public interface IWmpEffects
    {
        int Render(ref TimedLevel pLevels, IntPtr Hdc, ref RECT pRC);
        int MediaInfo(int lChannelCount, int lSampleRate, string bstrTitle);
        int GetCapabilities(ref int pdwCapabilities);
        int GetTitle(ref string bstrTitle);
        int GetPresetTitle([In] int nPreset, [MarshalAs(UnmanagedType.BStr)] ref string bstrPresetTitle);
        int GetPresetCount(ref int count);
        int SetCurrentPreset(int currentpreset);
        int GetCurrentPreset(ref int currentpreset);
        int DisplayPropertyPage(IntPtr hwndOwner);
        int GoFullScreen(bool fFullscreen);
        int RenderFullScreen(ref TimedLevel pLevels);
    }

    [ComVisible(true)]
    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    [Guid("695386EC-AA3C-4618-A5E1-DD9A8B987632")]
    public interface IWmpEffects2 : IWmpEffects
    {
        int SetCore(IntPtr pPlayer);
        int Create(IntPtr hwndParent);
        int Destroy();
        int NotifyNewMedia(IntPtr pMedia);
        int OnWindowMessage(int Msg, int WParam, int LParam, ref int plResultParam);
        int RenderWindowed(ref TimedLevel pData, bool fRequiredRender);
    }

    [ComVisible(true)]
    [StructLayout(LayoutKind.Sequential)]
    public struct Data
    {
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 0x400)]
        public byte[] Data0;
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 0x400)]
        public byte[] Data1;
    }

    [ComVisible(true)]
    public enum PlayerState
    {
        Stop_State,
        Pause_State,
        Play_State
    }

    [ComVisible(true)]
    [StructLayout(LayoutKind.Sequential)]
    public struct TimedLevel
    {
        public Data Frequency;
        public Data Waveform;
        public PlayerState State;
        public long TimeStamp;
    }

    [ComVisible(true)]
    [StructLayout(LayoutKind.Sequential)]
    public struct RECT
    {
        public int Left;
        public int Top;
        public int Right;
        public int Bottom;
    }
}

实现接口的类的代码如下

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
using WmpTestPlugin;
using System.IO;
using System.Windows.Forms;



    [ComVisible(true)]
    [Guid("C476FF24-5E5C-419d-9110-05EC2EED8511")]
    //[ProgId("WmpTestPlugin.WmpTest")]
    [ClassInterface(ClassInterfaceType.None)]
    public class TestPlugin : IWmpEffects2
    {
        [DllImport("user32.dll", EntryPoint = "GetClientRect")]
        private static extern bool getClientRect(IntPtr windowHandle, ref IntPtr rectangle);

        private const int EFFECT_CANGOFULLSCREEN = 1;
        private const int EFFECT_HASPROPERTYPAGE = 2;

        private const int S_OK = 0;
        private const int S_FALSE = 1;
        private const int E_ABORT = unchecked((int)0x80004004);
        private const int E_ACCESSDENIED = unchecked((int)0x80070005);
        private const int E_FAIL = unchecked((int)0x80004005);
        private const int E_HANDLE = unchecked((int)0x80070006);
        private const int E_INVALIDARG = unchecked((int)0x80070057);
        private const int E_NOINTERFACE = unchecked((int)0x80004002);
        private const int E_NOTIMPL = unchecked((int)0x80004001);
        private const int E_OUTOFMEMORY = unchecked((int)0x8007000E);
        private const int E_POINTER = unchecked((int)0x80004003);
        private const int E_UNEXPECTED = unchecked((int)0x8000FFFF);


        public TestPlugin()
        {
            _parentHwnd = IntPtr.Zero;
            _preset = 0;
            File.AppendAllText("C:\\wmp.txt", string.Format("{0} : Construct{1}", DateTime.Now.ToString(), Environment.NewLine));

        }

        ~TestPlugin()
        {
            File.AppendAllText("C:\\wmp.txt", string.Format("{0} : Deconstruct{1}", DateTime.Now.ToString(), Environment.NewLine));
        }

        #region IWmpEffects2 Members

        /// <summary>
        /// Set WMP core interface
        /// </summary>
        /// <param name="pPlayer"></param>
        /// <returns></returns>
        public int SetCore(IntPtr pPlayer)
        {
            File.AppendAllText("C:\\wmp.txt", string.Format("{0} : SetCore{1}", DateTime.Now.ToString(), Environment.NewLine));

            // release any existing WMP core interfaces
            //ReleaseCore();

            if (pPlayer == IntPtr.Zero)
                return S_OK;

            _playerCore = pPlayer;

            //connect up any events
            return S_OK;
        }

        /// <summary>
        /// Invoked when the visualization should be initialized.
        ///
        /// If hwndParent != NULL, RenderWindowed() will be called and the visualization
        /// should draw into the window specified by hwndParent. This will be the
        /// behavior when the visualization is hosted in a window.
        ///
        /// If hwndParent == NULL, Render() will be called and the visualization
        /// should draw into the DC passed to Render(). This will be the behavior when
        /// the visualization is hosted windowless (like in a skin for example).
        /// </summary>
        /// <param name="hwndParent"></param>
        /// <returns></returns>
        public int Create(IntPtr hwndParent)
        {
            File.AppendAllText("C:\\wmp.txt", string.Format("{0} : Create{1}", DateTime.Now.ToString(), Environment.NewLine));

            _parentHwnd = hwndParent;
            return S_OK;
        }

        /// <summary>
        /// Invoked when the visualization should be released.
        /// Any resources allocated for rendering should be released.
        /// </summary>
        /// <returns></returns>
        public int Destroy()
        {
            File.AppendAllText("C:\\wmp.txt", string.Format("{0} : Destroy{1}", DateTime.Now.ToString(), Environment.NewLine));
            _parentHwnd = IntPtr.Zero;
            return S_OK;
        }

        /// <summary>
        /// Invoked when a new media stream begins playing.
        /// The visualization can inspect this object for properties (like name or artist)
        /// that might be interesting for visualization.
        /// </summary>
        /// <param name="pMedia"></param>
        /// <returns></returns>
        public int NotifyNewMedia(IntPtr pMedia)
        {
            File.AppendAllText("C:\\wmp.txt", string.Format("{0} : NotifyNewMedia{1}", DateTime.Now.ToString(), Environment.NewLine));
            return S_OK;
        }

        /// <summary>
        /// Window messages sent to the parent window.
        /// </summary>
        /// <param name="Msg"></param>
        /// <param name="WParam"></param>
        /// <param name="LParam"></param>
        /// <param name="plResultParam"></param>
        /// <returns></returns>
        public int OnWindowMessage(int Msg, int WParam, int LParam, ref int plResultParam)
        {
            File.AppendAllText("C:\\wmp.txt", string.Format("{0} : OnWindowMessage{1}", DateTime.Now.ToString(), Environment.NewLine));
            // return S_OK only if the plugin has handled the window message
            // return S_FALSE to let the defWindowProc handle the message

            //if (_parentHwnd == IntPtr.Zero)
                //m_NonWindowedRenderer.OnWindowMessage(&m_RenderContext, msg, WParam, LParam, plResultParam);
            //else
            //    m_WindowedRenderer.OnWindowMessage(&m_RenderContext, msg, WParam, LParam, plResultParam);

            return S_FALSE;
        }

        /// <summary>
        /// Called when an effect should render itself to the screen.
        /// The fRequiredRender flag specifies if an update is required, otherwise the
        /// update is optional. This allows visualizations that are fairly static (for example,
        /// album art visualizations) to only render when the parent window requires it,
        /// instead of n times a second for dynamic visualizations.
        /// </summary>
        /// <param name="pData"></param>
        /// <param name="fRequiredRender"></param>
        /// <returns></returns>
        public int RenderWindowed(ref TimedLevel pData, bool fRequiredRender)
        {
            File.AppendAllText("C:\\wmp.txt", string.Format("{0} : RenderWindowed{1}", DateTime.Now.ToString(), Environment.NewLine));
            //windowed

            // NULL parent window should not happen 
            if (_parentHwnd == IntPtr.Zero)
                return E_UNEXPECTED;

            //RECT rect = new RECT();

            //TestPlugin.getClientRect(_parentHwnd, ref rect);

            //do render//

            return S_OK;
        }

        #endregion

        #region IWmpEffects Members

        /// <summary>
        /// Called when an effect should render itself to the screen.
        /// </summary>
        /// <param name="pLevels"></param>
        /// <param name="Hdc"></param>
        /// <param name="pRC"></param>
        /// <returns></returns>
        public int Render(ref TimedLevel pLevels, IntPtr Hdc, ref RECT pRC)
        {
            File.AppendAllText("C:\\wmp.txt", string.Format("{0} : Render{1}", DateTime.Now.ToString(), Environment.NewLine));
            //not windowed


            //do render
            return S_OK;
        }

        /// <summary>
        /// Everytime new media is loaded, this method is called to pass the
        /// number of channels (mono/stereo), the sample rate of the media, and the
        /// title of the media
        /// </summary>
        /// <param name="lChannelCount"></param>
        /// <param name="lSampleRate"></param>
        /// <param name="bstrTitle"></param>
        /// <returns></returns>
        public int MediaInfo(int lChannelCount, int lSampleRate, string bstrTitle)
        {
            File.AppendAllText("C:\\wmp.txt", string.Format("{0} : MediaInfo{1}", DateTime.Now.ToString(), Environment.NewLine));
            return S_OK;
        }

        /// <summary>
        /// Returns the capabilities of this effect. Flags that can be returned are:
        /// EFFECT_CANGOFULLSCREEN  -- effect supports full-screen rendering
        /// EFFECT_HASPROPERTYPAGE  -- effect supports a property page
        /// </summary>
        /// <param name="pdwCapabilities"></param>
        /// <returns></returns>
        public int GetCapabilities(ref int pdwCapabilities)
        {
            File.AppendAllText("C:\\wmp.txt", string.Format("{0} : GetCapabilities{1}", DateTime.Now.ToString(), Environment.NewLine));
            //no capabilities
            pdwCapabilities = EFFECT_HASPROPERTYPAGE;

            return S_OK;
        }

        /// <summary>
        /// Invoked when a host wants to obtain the title of the effect
        /// </summary>
        /// <param name="bstrTitle"></param>
        /// <returns></returns>
        public int GetTitle(ref string bstrTitle)
        {
            File.AppendAllText("C:\\wmp.txt", string.Format("{0} : GetTitle{1}", DateTime.Now.ToString(), Environment.NewLine));
            bstrTitle = "Test Wmp C# Plugin";
            return S_OK;
        }

        /// <summary>
        /// Invoked when a host wants to obtain the title of the given preset
        /// </summary>
        /// <param name="nPreset"></param>
        /// <param name="bstrPresetTitle"></param>
        /// <returns></returns>
        public int GetPresetTitle(int nPreset, ref string bstrPresetTitle)
        {
            File.AppendAllText("C:\\wmp.txt", string.Format("{0} : GetPresetTitle{1}", DateTime.Now.ToString(), Environment.NewLine));
            //bstrPresetTitle = "Default";
            return S_OK;
        }

        /// <summary>
        /// Invoked when a host wants to obtain the number of supported presets
        /// </summary>
        /// <param name="count"></param>
        /// <returns></returns>
        public int GetPresetCount(ref int count)
        {
            File.AppendAllText("C:\\wmp.txt", string.Format("{0} : GetPresetCount{1}", DateTime.Now.ToString(), Environment.NewLine));
            count = 1;
            return S_OK;
        }



        /// <summary>
        /// Invoked when a host wants to obtain the index of the current preset
        /// </summary>
        /// <param name="currentpreset"></param>
        /// <returns></returns>
        public int SetCurrentPreset(int currentpreset)
        {
            File.AppendAllText("C:\\wmp.txt", string.Format("{0} : SetCurrentPreset{1}", DateTime.Now.ToString(), Environment.NewLine));
            _preset = currentpreset;
            return S_OK;
        }

        /// <summary>
        /// Invoked when a host wants to obtain the index of the current preset
        /// </summary>
        /// <param name="currentpreset"></param>
        /// <returns></returns>
        public int GetCurrentPreset(ref int currentpreset)
        {
            File.AppendAllText("C:\\wmp.txt", string.Format("{0} : GetCurrentPreset{1}", DateTime.Now.ToString(), Environment.NewLine));
            currentpreset = _preset;
            return S_OK;
        }

        /// <summary>
        /// Invoked when a host wants to display the property page for the effect
        /// </summary>
        /// <param name="hwndOwner"></param>
        /// <returns></returns>
        public int DisplayPropertyPage(IntPtr hwndOwner)
        {
            File.AppendAllText("C:\\wmp.txt", string.Format("{0} : DisplayPropertyPage, Owner={1}{2}", DateTime.Now.ToString(), hwndOwner.ToString(), Environment.NewLine));
            MessageBox.Show("Hello Me!");
            return S_OK;
        }

        public int GoFullScreen(bool fFullscreen)
        {
            File.AppendAllText("C:\\wmp.txt", string.Format("{0} : GoFullScreen{1}", DateTime.Now.ToString(), Environment.NewLine));
            return S_OK;
        }

        public int RenderFullScreen(ref TimedLevel pLevels)
        {
            File.AppendAllText("C:\\wmp.txt", string.Format("{0} : RenderFullScreen{1}", DateTime.Now.ToString(), Environment.NewLine));
            return S_OK;
        }

        #endregion

        private IntPtr _parentHwnd;
        private int _preset;

        private IntPtr _playerCore;

    }

如您所见，我的代码非常空，实际上只不过是存根。我的调试很简单，但可以完成工作。

一旦使用强名称进行编译，就可以将其注册为：

regasm assemblyname.dll /tlb

，然后将其放入 gac 中。

打开regedit并添加以下内容 信息：

下 HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MediaPlayer\Objects\Effects

新密钥：WmpTestPlugin

在新键下添加一个新字符串 值：名称：classid 值： {C476FF24-5E5C-419d-9110-05EC2EED8511}

因此，我们构建了一个符合接口的插件，将其注册到 GAC 中并告诉媒体播放器它在那里。

如果您打开媒体播放器并右键单击可视化空间，将会出现一个菜单。在该菜单中将是我们的新插件。当您将鼠标向下移动到新项目时，WMP 将调用插件上的 GetPresetCount （这将记录到文件中）。然后 WMP 应该调用 GetPresetTitle 但它从来没有为我做。

如果您从菜单栏中打开“工具\选项”并选择“插件”选项卡，则可以选择新插件。如果您单击“属性”，WMP 将调用 GetCapability，然后调用 DisplayPropertyPage，并且会出现来自插件的消息框。然后 WMP 就崩溃了。在 C++ 版本中，FinalConstruct() 是在 CComCoClass 接口上调用的 - 我没有这个接口，也不知道它是什么。我认为它可能比我使用的级别低？

我尝试了很多方法来使其正常工作，包括更改方法声明。请有人看一下并提供帮助。我在网上寻找解决方案，但一无所获。

感谢您的阅读， 纳努克

Answer 1

在查看一些 Windows Shell 互操作代码后，我发现我应该对接口使用 [ComImport] 而不是 [ComVisible]。为了使签名等于已经注册的签名，我使用了 [PreserveSig]。接口继承还需要通过在父级中重新声明基接口来获得一些帮助。

我希望这对某人有帮助。

这里是工人阶级

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;

namespace WmpTestPlugin
{
    [ComImport]
    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    [Guid("695386EC-AA3C-4618-A5E1-DD9A8B987632")]
    public interface IWmpEffects2 : IWmpEffects
    {
        [PreserveSig]
        new int Render(ref TimedLevel pLevels, IntPtr Hdc, ref RECT pRC);
        [PreserveSig]
        new int MediaInfo(int lChannelCount, int lSampleRate, string bstrTitle);
        [PreserveSig]
        new int GetCapabilities(ref int pdwCapabilities);
        [PreserveSig]
        new int GetTitle(ref string bstrTitle);
        [PreserveSig]
        new int GetPresetTitle(int nPreset, ref string bstrPresetTitle);
        [PreserveSig]
        new int GetPresetCount(ref int count);
        [PreserveSig]
        new int SetCurrentPreset(int currentpreset);
        [PreserveSig]
        new int GetCurrentPreset(ref int currentpreset);
        [PreserveSig]
        new int DisplayPropertyPage(IntPtr hwndOwner);
        [PreserveSig]
        new int GoFullScreen(bool fFullscreen);
        [PreserveSig]
        new int RenderFullScreen(ref TimedLevel pLevels);

        [PreserveSig]
        int SetCore(IntPtr pPlayer);
        [PreserveSig]
        int Create(IntPtr hwndParent);
        [PreserveSig]
        int Destroy();
        [PreserveSig]
        int NotifyNewMedia(IntPtr pMedia);
        [PreserveSig]
        int OnWindowMessage(int Msg, int WParam, int LParam, ref int plResultParam);
        [PreserveSig]
        int RenderWindowed(ref TimedLevel pData, bool fRequiredRender);
    }

    [ComImport]
    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    [Guid("D3984C13-C3CB-48e2-8BE5-5168340B4F35")]
    public interface IWmpEffects
    {
        [PreserveSig]
        int Render(ref TimedLevel pLevels, IntPtr Hdc, ref RECT pRC);
        [PreserveSig]
        int MediaInfo(int lChannelCount, int lSampleRate, string bstrTitle);
        [PreserveSig]
        int GetCapabilities(ref int pdwCapabilities);
        [PreserveSig]
        int GetTitle(ref string bstrTitle);
        [PreserveSig]
        int GetPresetTitle(int nPreset, ref string bstrPresetTitle);
        [PreserveSig]
        int GetPresetCount(ref int count);
        [PreserveSig]
        int SetCurrentPreset(int currentpreset);
        [PreserveSig]
        int GetCurrentPreset(ref int currentpreset);
        [PreserveSig]
        int DisplayPropertyPage(IntPtr hwndOwner);
        [PreserveSig]
        int GoFullScreen(bool fFullscreen);
        [PreserveSig]
        int RenderFullScreen(ref TimedLevel pLevels);
    }


    //[ComVisible(true)]
    [StructLayout(LayoutKind.Sequential)]
    public struct Data
    {
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 0x400)]
        public byte[] Data0;
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 0x400)]
        public byte[] Data1;
    }

    //[ComVisible(true)]
    public enum PlayerState
    {
        Stop_State,
        Pause_State,
        Play_State
    }

    //[ComVisible(true)]
    [StructLayout(LayoutKind.Sequential)]
    public struct TimedLevel
    {
        public Data Frequency;
        public Data Waveform;
        public PlayerState State;
        public long TimeStamp;
    }

    //[ComVisible(true)]
    [StructLayout(LayoutKind.Sequential)]
    public struct RECT
    {
        public int Left;
        public int Top;
        public int Right;
        public int Bottom;
        public int Width { get { return this.Right - this.Left; } }
        public int Height { get { return this.Bottom - this.Top; } }
    }
}