IMessageFilter::HandleInComingCall

A version of this page is also available for

Windows Embedded CE 6.0 R3

4/8/2010

This method is an object-based method that provides the ability to filter or reject incoming calls (or call backs) to an object or a process.

This method is called prior to each method invocation originating outside the current process.

Syntax

DWORD HandleInComingCall(
  DWORD dwCallType,
  HTASK threadIDCaller,
  DWORD dwTickCount,
  LPINTERFACEINFO lpInterfaceInfo 
);

Parameters

• dwCallType
  [in] Kind of incoming call that has been received.

  Valid values are from the enumeration CALLTYPE.

• threadIDCaller
  [in] Handle of the task calling this task.

• dwTickCount
  [in] Elapsed tick count since the outgoing call was made if dwCallType is not CALLTYPE_TOPLEVEL.

  If dwCallType is CALLTYPE_TOPLEVEL, dwTickCount should be ignored.

• lpInterfaceInfo
  [in] Pointer to an INTERFACEINFO structure, which identifies the object, the interface, and the method making the call.

  In the case of DDE calls, lpInterfaceInfo can be NULL because the DDE layer does not return interface information.

Return Value

• SERVERCALL_ISHANDLED
  The application might be able to process the call.

• SERVERCALL_REJECTED
  The application cannot handle the call due to an unforeseen problem, such as network unavailability, or if it is in the process of terminating.

• SERVERCALL_RETRYLATER
  The application cannot handle the call at this time.

  For example, an application might return this value when it is in a user-controlled modal state.

Remarks

If implemented, IMessageFilter::HandleInComingCall is called by COM when an incoming COM message is received.

Depending on an application's current state, a call is either accepted and processed or rejected (permanently or temporarily).

If SERVERCALL_ISHANDLED is returned, the application may be able to process the call, though success depends on the interface for which the call is destined.

If the call cannot be processed, COM returns RPC_E_CALL_REJECTED.

Input-synchronized and asynchronous calls are dispatched even if the application returns SERVERCALL_REJECTED or SERVERCALL_RETRYLATER.

IMessageFilter::HandleInComingCall should not be used to hold off updates to objects during operations such as band printing. For that purpose, use IViewObject::Freeze.

You can also use IMessageFilter::HandleInComingCall to set up the application's state so the call can be processed in the future.

To determine whether the platform supports this interface, see Determining Supported COM APIs.

Requirements

See Also

Reference

IViewObject::Freeze