WM_DEVICECHANGE message

最新推荐文章于 2024-05-24 22:00:18 发布

kn_c

最新推荐文章于 2024-05-24 22:00:18 发布

阅读量547

点赞数

msdn:http://msdn.microsoft.com/en-us/library/windows/desktop/aa363480%28v=vs.85%29.aspx

otifies an application of a change to the hardware configuration of a device or the computer.

A window receives this message through its WindowProc function.

 
   C++ 
  
    LRESULT CALLBACK WindowProc(HWND   hwnd,     // handle to window
                            UINT   uMsg,     // WM_DEVICECHANGE
                            WPARAM wParam,   // device-change event
                            LPARAM lParam ); // event-specific data

Parameters

hwnd

A handle to the window.

uMsg

The WM_DEVICECHANGE identifier.

wParam

The event that has occurred. This parameter can be one of the following values from the Dbt.h header file.

Value	Meaning
DBT_CONFIGCHANGECANCELED 0x0019	A request to change the current configuration (dock or undock) has been canceled.
DBT_CONFIGCHANGED 0x0018	The current configuration has changed, due to a dock or undock.
DBT_CUSTOMEVENT 0x8006	A custom event has occurred.
DBT_DEVICEARRIVAL 0x8000	A device or piece of media has been inserted and is now available.
DBT_DEVICEQUERYREMOVE 0x8001	Permission is requested to remove a device or piece of media. Any application can deny this request and cancel the removal.
DBT_DEVICEQUERYREMOVEFAILED 0x8002	A request to remove a device or piece of media has been canceled.
DBT_DEVICEREMOVECOMPLETE 0x8004	A device or piece of media has been removed.
DBT_DEVICEREMOVEPENDING 0x8003	A device or piece of media is about to be removed. Cannot be denied.
DBT_DEVICETYPESPECIFIC 0x8005	A device-specific event has occurred.
DBT_DEVNODES_CHANGED 0x0007	A device has been added to or removed from the system.
DBT_QUERYCHANGECONFIG 0x0017	Permission is requested to change the current configuration (dock or undock).
DBT_USERDEFINED 0xFFFF	The meaning of this message is user-defined.

lParam

A pointer to a structure that contains event-specific data. Its format depends on the value of the wParam parameter. For more information, refer to the documentation for each event.

Return value

Return TRUE to grant the request.

Return BROADCAST_QUERY_DENY to deny the request.

Remarks

For devices that offer software-controllable features, such as ejection and locking, the system typically sends a DBT_DEVICEREMOVEPENDING message to let applications and device drivers end their use of the device gracefully. If the system forcibly removes a device, it may not send a DBT_DEVICEQUERYREMOVE message before doing so.