WM_DEVICECHANGE message

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

A window receives this message through its WindowProc function.

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

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.

Expand table

Value	Meaning
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_CONFIGCHANGED 0x0018	The current configuration has changed, due to a dock or undock.
DBT_CONFIGCHANGECANCELED 0x0019	A request to change the current configuration (dock or undock) has been canceled.
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_DEVICEREMOVEPENDING 0x8003	A device or piece of media is about to be removed. Cannot be denied.
DBT_DEVICEREMOVECOMPLETE 0x8004	A device or piece of media has been removed.
DBT_DEVICETYPESPECIFIC 0x8005	A device-specific event has occurred.
DBT_CUSTOMEVENT 0x8006	A custom event has occurred.
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 TRUE to grant the request.

Return BROADCAST_QUERY_DENY to deny the request.

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.

DBT_CONFIGCHANGECANCELED

DBT_CONFIGCHANGED

DBT_CUSTOMEVENT

DBT_DEVICEARRIVAL

DBT_DEVICEQUERYREMOVE

DBT_DEVICEQUERYREMOVEFAILED

DBT_DEVICEREMOVECOMPLETE

DBT_DEVICEREMOVEPENDING

DBT_DEVICETYPESPECIFIC

DBT_DEVNODES_CHANGED

DBT_QUERYCHANGECONFIG

DBT_USERDEFINED