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

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.

Requirements

Minimum supported client
Windows XP
Minimum supported server
Windows Server 2003
Header
Winuser.h (include Windows.h or Dbt.h)

See also

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