CDeferredCommand Class

CDeferredCommand class hierarchy

Deferred commands are queued by calls to methods on the IQueueCommand interface and are exposed by the filter graph manager and by some filters. A successful call to one of these methods returns an IDeferredCommand interface representing the queued command.

A CDeferredCommand object represents a single deferred command and exposes the IDeferredCommand interface as well as other methods that permit time checks and actual execution. A CDeferredCommand object contains a reference to the CCmdQueue object on which it is queued.

Reference counts control the lifetime of the CDeferredCommand class. When calling the CDeferredCommand::Invoke member function, the calling application gets an interface pointer that is reference-counted, and the CCmdQueue object also holds a reference count on the deferred command. Calling the IDeferredCommand::Cancel member function takes the deferred command off the command queue and thus reduces the reference count by one. Once taken off the queue, the command cannot be put back on the queue.

Protected Data Members

m_bStream Flag for stream time or presentation time. to be passed to the invoked method.
m_Dispatch Accesses the ITypeInfo interface.
m_dispidMethod Method on the interface to run.
m_DispParams CDispParams object containing the DISPPARAMS parameter list
m_hrResult Stores the returned HRESULT value.
m_iid Globally unique identifier (GUID) of the interface.
m_pQueue Pointer to the CCmdQueue object that exposes the IQueueCommand interface.
m_pUnk IUnknown pointer to the interface on which the command will be run.
m_pvarResult Resulting information, if any, from the invoked method.
m_time Time at which the command will be run.
m_wFlags Flags specifying the context of the invocation.

Member Functions

CDeferredCommand Constructs a CDeferredCommand object.
GetFlags Retrieves the context flags associated with the deferred command.
GetIID Retrieves the interface identifier (IID) of the interface on which the method will be run.
GetMethod Retrieves the dispatch identifier of the method to be run.
GetParams Retrieves the DISPPARAMS argument list to the method.
GetResult Retrieves the resulting argument list, if one exists.
GetTime Retrieves the time when the method will be run.
Invoke Provides access to methods and properties exposed by an object.
IsStreamTime Specifies whether the command is to be run at stream time or presentation time.

Implemented IDeferredCommand Methods

Cancel Cancels a previously queued CDeferredCommand::Invoke request.
Confidence Not currently implemented.
Postpone Specifies a new presentation time for a previously queued command.
GetHResult Retrieves the HRESULT value of the invoked method.

Implemented INonDelegatingUnknown Methods

NonDelegatingQueryInterface Retrieves a specified reference-counted interface.

CDeferredCommand::Cancel

CDeferredCommand Class

Cancels a previously queued CDeferredCommand::Invoke request.

Syntax

HRESULT Cancel(void);

Return Value

Returns VFW_E_ALREADY_CANCELLED if m_pQueue is NULL. Returns an HRESULT from CCmdQueue::Remove if the call generates an error. Returns S_OK if successful.

Remarks

This member function implements the IDeferredCommand::Cancel method.

CDeferredCommand::CDeferredCommand

CDeferredCommand Class

Constructs a CDeferredCommand object.

Syntax

CDeferredCommand(
    CCmdQueue *pQ,
    LPUNKNOWN pUnk,
    HRESULT *phr,
    LPUNKNOWN pUnkExecutor,
    REFTIME time,
    GUID *iid,
    long dispidMethod,
    short wFlags,
    long cArgs,
    VARIANT *pDispParams,
    VARIANT *pvarResult,
    short *puArgErr,
    BOOL bStream
    );

Parameters

pQ
Pointer to an object that exposes the IQueueCommand interface.
pUnk
Pointer to the outer IUnknown interface for aggregation.
phr
Pointer to a returned HRESULT value.
pUnkExecutor
Pointer to the object that will carry out this command.
time
Time at which the command will be run.
iid
Pointer to the globally unique identifier (GUID) of the interface that contains the method.
dispidMethod
Method on the interface to call.
wFlags
Context of the invocation.
cArgs
Number of arguments passed.
pDispParams
Pointer to a list of argument variant types.
pvarResult
Pointer to a returned variant type list, if any.
puArgErr
Pointer to the last argument in the pDispParams parameter list with an error.
bStream
Value indicating whether the deferred command time is in stream time (TRUE) or presentation time (FALSE).

Return Value

No return value.

CDeferredCommand::Confidence

CDeferredCommand Class

This method is not currently implemented and returns E_NOTIMPL.

Syntax

HRESULT Confidence(
    LONG *pConfidence
    );

Parameters

pConfidence
Pointer to the confidence level.

Return Value

Returns E_NOTIMPL.

Remarks

For information about implementing this method, see IDeferredCommand::Confidence.

CDeferredCommand::GetFlags

CDeferredCommand Class

Retrieves the context flags associated with the deferred command.

Syntax

short GetFlags(void);

Return Value

The value retrieved will be one of the following:

DISPATCH_METHOD Run the member as a method. If a property has the same name, both this and the DISPATCH_PROPERTYGET flag can be set.
DISPATCH_PROPERTYGET The member is being retrieved as a property or data member.
DISPATCH_PROPERTYPUT The member is being changed as a property or data member.
DISPATCH_PROPERTYPUTREF The member is being changed via a reference assignment, rather than a value assignment. This flag is valid only when the property accepts a reference to an object.

CDeferredCommand::GetHResult

CDeferredCommand Class

Retrieves the HRESULT value from the invoked command.

Syntax

HRESULT GetHResult(
    HRESULT *phrResult
    );

Parameters

phrResult
Pointer to the HRESULT value.

Return Value

Returns E_ABORT if m_pQueue is NULL. Otherwise, returns S_OK.

Remarks

This member function implements the IDeferredCommand::GetHResult method.

CDeferredCommand::GetIID

CDeferredCommand Class

Retrieves the interface identifier (IID) of the interface on which the method will be run.

Syntax

REFIID GetIID(void);

Return Value

Returns the IID of the interface on which the method will be run.

CDeferredCommand::GetMethod

CDeferredCommand Class

Retrieves the dispatch identifier (DISPID) of the method to be run.

Syntax

long GetMethod(void);

Return Value

Returns the DISPID of the method to run.

CDeferredCommand::GetParams

CDeferredCommand Class

Retrieves the DISPPARAMS argument list to the method.

Syntax

DISPPARAMS* GetParams(void);

Return Value

Returns a DISPPARAMS argument list.

CDeferredCommand::GetResult

CDeferredCommand Class

Retrieves the resulting argument list, if one exists.

Syntax

VARIANT* GetResult(void);

Return Value

Returns a VARIANT containing the method's argument list, if it exists.

CDeferredCommand::GetTime

CDeferredCommand Class

Retrieves the time at which the method will be run.

Syntax

CRefTime GetTime(void);

Return Value

Returns a CRefTime object containing a reference time.

CDeferredCommand::Invoke

CDeferredCommand Class

Provides access to methods and properties exposed by an object.

Syntax

HRESULT Invoke(void);

Return Value

Returns VFW_E_ALREADY_CANCELLED if m_pQueue is NULL. Otherwise, returns the HRESULT resulting from a call to IDispatch::GetTypeInfo or IUnknown::QueryInterface.

CDeferredCommand::IsStreamTime

CDeferredCommand Class

Specifies whether the command is to be run at stream time or presentation time.

Syntax

BOOL IsStreamTime(void);

Return Value

Returns TRUE if set to stream time; otherwise, returns FALSE.

CDeferredCommand::NonDelegatingQueryInterface

CDeferredCommand Class

Retrieves a specified reference-counted interface.

Syntax

HRESULT NonDelegatingQueryInterface(
    REFIID riid,
    void **ppv
    );

Parameters

riid
Reference identifier.
ppv
Address of a pointer to the interface.

Return Value

Returns E_POINTER if ppv is invalid. Returns NOERROR if the query is successful or E_NOINTERFACE if it is not.

Remarks

Returns pointers to the IDeferredCommand and IUnknown interfaces by default. Override this method to publish any additional interfaces implemented by the derived class.
This member function implements the INonDelegatingUnknown::NonDelegatingQueryInterface method.

CDeferredCommand::Postpone

CDeferredCommand Class

Specifies a new presentation time for a previously queued command.

Syntax

HRESULT Postpone(
    REFTIME newtime
    );

Parameters

newtime
New presentation time.

Return Value

Returns VFW_E_TIME_ALREADY_PASSED if newtime is already passed. Otherwise, returns an HRESULT resulting from a call to CCmdQueue::Remove (when extracting from the list) or CCmdQueue::Insert (when reinserting with the changed time).

Remarks

This member function implements the IDeferredCommand::Postpone method.

m_bStream	Flag for stream time or presentation time. to be passed to the invoked method.
m_Dispatch	Accesses the ITypeInfo interface.
m_dispidMethod	Method on the interface to run.
m_DispParams	CDispParams object containing the DISPPARAMS parameter list
m_hrResult	Stores the returned HRESULT value.
m_iid	Globally unique identifier (GUID) of the interface.
m_pQueue	Pointer to the CCmdQueue object that exposes the IQueueCommand interface.
m_pUnk	IUnknown pointer to the interface on which the command will be run.
m_pvarResult	Resulting information, if any, from the invoked method.
m_time	Time at which the command will be run.
m_wFlags	Flags specifying the context of the invocation.

CDeferredCommand	Constructs a CDeferredCommand object.
GetFlags	Retrieves the context flags associated with the deferred command.
GetIID	Retrieves the interface identifier (IID) of the interface on which the method will be run.
GetMethod	Retrieves the dispatch identifier of the method to be run.
GetParams	Retrieves the DISPPARAMS argument list to the method.
GetResult	Retrieves the resulting argument list, if one exists.
GetTime	Retrieves the time when the method will be run.
Invoke	Provides access to methods and properties exposed by an object.
IsStreamTime	Specifies whether the command is to be run at stream time or presentation time.

Cancel	Cancels a previously queued CDeferredCommand::Invoke request.
Confidence	Not currently implemented.
Postpone	Specifies a new presentation time for a previously queued command.
GetHResult	Retrieves the HRESULT value of the invoked method.

DISPATCH_METHOD	Run the member as a method. If a property has the same name, both this and the DISPATCH_PROPERTYGET flag can be set.
DISPATCH_PROPERTYGET	The member is being retrieved as a property or data member.
DISPATCH_PROPERTYPUT	The member is being changed as a property or data member.
DISPATCH_PROPERTYPUTREF	The member is being changed via a reference assignment, rather than a value assignment. This flag is valid only when the property accepts a reference to an object.