RegisterHotKey

The RegisterHotKey function defines a system-wide hot key.

BOOL RegisterHotKey(
  HWND hWnd,         // window to receive hot-key notification
  int id,            // identifier of hot key
  UINT fsModifiers,  // key-modifier flags
  UINT vk            // virtual-key code
);
 

Parameters

hWnd

Handle to the window that will receive WM_HOTKEY messages generated by the hot key. If this parameter is NULL, WM_HOTKEY messages are posted to the message queue of the calling thread and must be processed in the message loop.

id

Specifies the identifier of the hot key. No other hot key in the calling thread should have the same identifier. An application must specify a value in the range 0x0000 through 0xBFFF. A shared dynamic-link library (DLL) must specify a value in the range 0xC000 through 0xFFFF (the range returned by the GlobalAddAtom function). To avoid conflicts with hot-key identifiers defined by other shared DLLs, a DLL should use the GlobalAddAtom function to obtain the hot-key identifier.

fsModifiers

Specifies keys that must be pressed in combination with the key specified by the nVirtKey parameter in order to generate the WM_HOTKEY message. The fsModifiers parameter can be a combination of the following values.

Value	Meaning
MOD_ALT	Either alt key must be held down.
MOD_CONTROL	Either ctrl key must be held down.
MOD_SHIFT	Either shift key must be held down.
MOD_WIN	Either WINDOWS key was held down. These keys are labeled with the Microsoft Windows logo.

vk

Specifies the virtual-key code of the hot key.

Return Values

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

Remarks

When a key is pressed, the system looks for a match against all hot keys. Upon finding a match, the system posts the WM_HOTKEY message to the message queue of the thread that registered the hot key. This message is posted to the beginning of the queue so it is removed by the next iteration of the message loop.

This function cannot associate a hot key with a window created by another thread.

RegisterHotKey fails if the keystrokes specified for the hot key have already been registered by another hot key.

If the window identified by the hWnd parameter already registered a hot key with the same identifier as that specified by the id parameter, the new values for the fsModifiers and vk parameters replace the previously specified values for these parameters.

Windows CE: Windows CE versions 2.0 and later support an additional flag, called MOD_KEYUP, for the fsModifiers parameter. If you set the MOD_KEYUP flag, the window will be sent a WM_HOTKEY message on a key up event as well as on a key down event.

RegisterHotKey can be used to register hot keys across threads.

QuickInfo

  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Unsupported.
  Header: Declared in winuser.h.
  Import Library: Use user32.lib.

See Also

Keyboard Input Overview, Keyboard Input Functions, GlobalAddAtom, UnregisterHotKey, WM_HOTKEY