This tutorial pertains only to applications written in C++. See DirectMusic Visual Basic Tutorials.

The first step in creating a tool for DirectMusic in C++ is to declare a class derived from IDirectMusicTool.

Here is the declaration for the sample CEchoTool class:

class CEchoTool : public IDirectMusicTool
{
public:
  CEchoTool();
  ~CEchoTool();
 
public:
// IUnknown
  virtual STDMETHODIMP QueryInterface(const IID &iid, void **ppv);
  virtual STDMETHODIMP_(ULONG) AddRef();
  virtual STDMETHODIMP_(ULONG) Release();
 
// IDirectMusicTool
  HRESULT STDMETHODCALLTYPE Init(
          IDirectMusicGraph* pGraph);
  HRESULT STDMETHODCALLTYPE GetMsgDeliveryType(
          DWORD* pdwDeliveryType);
  HRESULT STDMETHODCALLTYPE GetMediaTypeArraySize(
          DWORD* pdwNumElements);
  HRESULT STDMETHODCALLTYPE GetMediaTypes(
          DWORD** padwMediaTypes,
          DWORD dwNumElements);
  HRESULT STDMETHODCALLTYPE ProcessPMsg(
          IDirectMusicPerformance* pPerf,
          DMUS_PMSG* pDMUS_PMSG);
  HRESULT STDMETHODCALLTYPE Flush(
         IDirectMusicPerformance* pPerf,
         DMUS_PMSG* pDMUS_PMSG,
         REFERENCE_TIME rtTime);
private:
  long m_cRef;                // Reference counter
  DWORD m_dwEchoNum;          // Number of echoes to generate
  MUSIC_TIME m_mtDelay;       // Delay time between echoes
  CRITICAL_SECTION m_CrSec;   // To make SetEchoNum() 
                              //   and SetDelay() thread-safe
public:
// Public class methods
  void SetEchoNum(DWORD);
  void SetDelay(MUSIC_TIME);
};

Next: Step 2: Define the IUnknown Methods