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 win32 msgs: WM_POWERBROADCAST

The WM_POWERBROADCAST message is broadcast to an application to notify it of power-management events.

A window receives this message through its WindowProc function.

    LRESULT CALLBACK WindowProc(
      HWND hwnd,       // handle to window
      UINT uMsg,       // WM_POWERBROADCAST
      WPARAM wParam,   // power-management event
      LPARAM lParam    // function-specific data
    );

Parameters

• wParam Specifies the power-management event. This parameter can be one of the following events. Event Meaning PBT_APMBATTERYLOW Battery power is low. PBT_APMOEMEVENT OEM-defined event occurred. PBT_APMPOWERSTATUSCHANGE Power status has changed. PBT_APMQUERYSUSPEND Request for permission to suspend. PBT_APMQUERYSUSPENDFAILED Suspension request denied. PBT_APMRESUMEAUTOMATIC Operation resuming automatically after event. PBT_APMRESUMECRITICAL Operation resuming after critical suspension. PBT_APMRESUMESUSPEND Operation resuming after suspension. PBT_APMSUSPEND System is suspending operation.
• lParam Function-specific data. For most events, this parameter is reserved and not used. However, if wParam is one of the resume events (PBT_APMRESUME*), the lParam parameter can specify the PBTF_APMRESUMEFROMFAILURE flag. This flag indicates that a suspend operation failed after the PBT_APMSUSPEND event was broadcast.

Return Values

Return TRUE to grant a request.

Return BROADCAST_QUERY_DENY to deny a request.

Requirements

  Windows NT/2000 or later: Requires Windows NT 4.0 or later.
  Windows 95/98/Me: Requires Windows 95 or later.
  Header: Declared in Winuser.h; include Windows.h.

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Notebook exported on Monday, 7 July 2008, 18:56:50 PM Eastern Daylight Time