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CHANGEFILTERSTRUCT structure

Contains extended result information obtained by calling the ChangeWindowMessageFilterEx function.

Syntax


typedef struct tagCHANGEFILTERSTRUCT {
  DWORD cbSize;
  DWORD ExtStatus;
} CHANGEFILTERSTRUCT, *PCHANGEFILTERSTRUCT;

Members

cbSize

Type: DWORD

The size of the structure, in bytes. Must be set to sizeof(CHANGEFILTERSTRUCT), otherwise the function fails with ERROR_INVALID_PARAMETER.

ExtStatus

Type: DWORD

If the function succeeds, this field contains one of the following values.

ValueMeaning
MSGFLTINFO_NONE
0

See the Remarks section. Applies to MSGFLT_ALLOW and MSGFLT_DISALLOW.

MSGFLTINFO_ALLOWED_HIGHER
3

The message is allowed at a scope higher than the window. Applies to MSGFLT_DISALLOW.

MSGFLTINFO_ALREADYALLOWED_FORWND
1

The message has already been allowed by this window's message filter, and the function thus succeeded with no change to the window's message filter. Applies to MSGFLT_ALLOW.

MSGFLTINFO_ALREADYDISALLOWED_FORWND
2

The message has already been blocked by this window's message filter, and the function thus succeeded with no change to the window's message filter. Applies to MSGFLT_DISALLOW.

 

Remarks

Certain messages whose value is smaller than WM_USER are required to pass through the filter, regardless of the filter setting. There will be no effect when you attempt to use this function to allow or block such messages.

An application may use the ChangeWindowMessageFilter function to allow or block a message in a process-wide manner. If the message is allowed by either the process message filter or the window message filter, it will be delivered to the window.

The following table lists the possible values returned in ExtStatus.

Message already allowed at higher scopeMessage already allowed by window's message filterOperation requestedIndicator returned in ExtStatus on success
NoNoMSGFLT_ALLOWMSGFLTINFO_NONE
NoNoMSGFLT_DISALLOWMSGFLTINFO_ALREADYDISALLOWED_FORWND
NoNoMSGFLT_RESETMSGFLTINFO_NONE
NoYesMSGFLT_ALLOWMSGFLTINFO_ALREADYALLOWED_FORWND
NoYesMSGFLT_DISALLOWMSGFLTINFO_NONE
NoYesMSGFLT_RESETMSGFLTINFO_NONE
YesNoMSGFLT_ALLOWMSGFLTINFO_NONE
YesNoMSGFLT_DISALLOWMSGFLTINFO_ALLOWED_HIGHER
YesNoMSGFLT_RESETMSGFLTINFO_NONE
YesYesMSGFLT_ALLOWMSGFLTINFO_ALREADYALLOWED_FORWND
YesYesMSGFLT_DISALLOWMSGFLTINFO_ALLOWED_HIGHER
YesYesMSGFLT_RESETMSGFLTINFO_NONE

 

Requirements

Minimum supported client

Windows 7 [desktop apps only]

Minimum supported server

Windows Server 2008 R2 [desktop apps only]

Header

Winuser.h (include Windows.h)

See also

ChangeWindowMessageFilterEx

 

 

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