The CMediaControl class provides base class handling of the IDispatch methods of the dual-interface IMediaControl. It leaves as pure virtual the properties and methods of the IMediaControl interface.
Typically, the filter graph manager is the only object that implements the IMediaControl interface. (Filters implement the IMediaFilter interface, inherited by IBaseFilter, to receive control commands from the filter graph manager.) Therefore, this class library is of limited use to filter developers.
The CMediaControl::GetIDsOfNames, CMediaControl::GetTypeInfo, CMediaControl::GetTypeInfoCount, and CMediaControl::Invoke member functions are standard implementations of the IDispatch methods using the CBaseDispatch class (and a type library) to parse the commands and pass them to the pure virtual methods of the IMediaControl interface.
The IMediaControl methods, defined in control.odl, are left as pure virtual.
Member Functions
| Name | Description |
| CMediaControl | Constructs a CMediaControl object. |
Implemented INonDelegatingUnknown Methods
| Name | Description |
| NonDelegatingQueryInterface | Returns a specified reference-counted interface. |
Implemented IDispatch Methods
| Name | Description |
| GetIDsOfNames | Maps a single member and an optional set of parameters to a corresponding set of integer dispatch identifiers (DISPIDs), which can be used during subsequent calls to the CMediaControl::Invoke method. |
| GetTypeInfo | Retrieves a type-information object, which can retrieve the type information for an interface. |
| GetTypeInfoCount | Retrieves the number of type-information interfaces provided by an object. |
| Invoke | Provides access to properties and methods exposed by an object. |
Constructs a CMediaControl object.
CMediaControl(
const TCHAR *pName,
LPUNKNOWN pUnk
);
No return value.
Allocate the pName parameter in static memory. This name appears on the debugging terminal upon creation and deletion of the object.
Maps a single member function and an optional set of parameters to a corresponding set of integer dispatch identifiers (DISPIDs), which can be used upon subsequent calls to the CMediaControl::Invoke member function.
HRESULT GetIDsOfNames(
REFIID riid,
OLECHAR ** rgszNames,
UINT cNames,
LCID lcid,
DISPID * rgdispid
);
Returns one of the following values.
| Value | Meaning |
| DISP_E_UNKNOWN_CLSID | The CLSID was not recognized. |
| DISP_E_UNKNOWNNAME | One or more of the names were not known. The returned DISPIDs contain DISPID_UNKNOWN for each entry that corresponds to an unknown name. |
| E_OUTOFMEMORY | Out of memory. |
| S_OK | Success. |
Retrieves a type-information object, which can retrieve the type information for an interface.
HRESULT GetTypeInfo(
UINT itinfo,
LCID lcid,
ITypeInfo ** pptinfo
);
Returns an E_POINTER if pptinfo is invalid. Returns TYPE_E_ELEMENTNOTFOUND if itinfo is not zero. Returns S_OK if is successful. Otherwise, returns an HRESULT from one of the calls to retrieve the type. The HRESULT indicates the error and can be one of the following standard constants, or other values not listed:
| Value | Meaning |
| E_FAIL | Failure. |
| E_POINTER | Null pointer argument. |
| E_INVALIDARG | Invalid argument. |
| S_OK or NOERROR | Success. |
Retrieves the number of type-information interfaces provided by an object.
HRESULT GetTypeInfoCount(
UINT * pctinfo
);
Returns E_POINTER if pctinfo is invalid; otherwise, returns S_OK.
Provides access to properties and methods exposed by an object.
HRESULT Invoke(
DISPID dispidMember,
REFIID riid,
LCID lcid,
WORD wFlags,
DISPPARAMS * pdispparams,
VARIANT * pvarResult,
EXCEPINFO * pexcepinfo,
UINT * puArgErr
);
Returns DISP_E_UNKNOWNINTERFACE if riid is not IID_NULL. Returns one of the error codes from CMediaControl::GetTypeInfo if the call fails. Otherwise, returns the HRESULT from the call to IDispatch::Invoke.
Returns a specified reference-counted interface.
HRESULT NonDelegatingQueryInterface(
REFIID riid,
void **ppv
);
Returns E_POINTER if ppv is invalid. Returns NOERROR if the query is successful or E_NOINTERFACE if it is not.
Returns pointers to the IMediaControl and IUnknown interfaces by default. Override this member function to publish any additional interfaces implemented by the derived class.
This member function implements the INonDelegatingUnknown::NonDelegatingQueryInterface method.
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