GetAsyncKeyState
The GetAsyncKeyState
function determines whether a key is up or down at the time the function is
called, and whether the key was pressed after a previous call to GetAsyncKeyState.
SHORT GetAsyncKeyState(
|
int vKey |
// virtual-key code |
|
); |
|
Parameters
vKey
Specifies one
of 256 possible virtual-key codes.
Windows
NT: You can use left- and
right-distinguishing constants to specify certain keys. See the Remarks
section for further information.
Windows
95: Windows 95 does not support the
left- and right-distinguishing constants available on Windows NT.
Return Values
If the
function succeeds, the return value specifies whether the key was pressed since
the last call to GetAsyncKeyState, and whether the key is currently up
or down. If the most significant bit is set, the key is down, and if the least
significant bit is set, the key was pressed after the previous call to GetAsyncKeyState.
The return value is zero if a window in another thread or process currently has
the keyboard focus.
Windows
95: Windows 95 does not support the
left- and right-distinguishing constants. If you call GetAsyncKeyState
on the Windows 95 platform with these constants, the return value is zero.
Remarks
You can use
the virtual-key code constants VK_SHIFT, VK_CONTROL, and VK_MENU as values for
the vKey parameter. This gives the state of the SHIFT, CTRL, or ALT keys without
distinguishing between left and right.
Windows
NT: You can use the following
virtual-key code constants as values for vKey to distinguish between the
left and right instances of those keys:
|
VK_LSHIFT |
VK_RSHIFT |
|
VK_LCONTROL |
VK_RCONTROL |
|
VK_LMENU |
VK_RMENU |
These left-
and right-distinguishing constants are only available when you call the GetKeyboardState, SetKeyboardState, GetAsyncKeyState, GetKeyState, and MapVirtualKey functions.
Windows
95: Windows 95 does not support the
left- and right-distinguishing constants, and returns 0 when you use these
constants.
The GetAsyncKeyState
function works with mouse buttons. However, it checks on the state of the
physical mouse buttons, not on the logical mouse buttons that the physical
buttons are mapped to. For example, the call GetAsyncKeyState(VK_LBUTTON)
always returns the state of the left physical mouse button, which may mapped to
the left or right logical mouse button. You can determine the system s current
mapping of physical mouse buttons to logical mouse buttons by calling
GetSystemMetrics(SM_SWAPBUTTON)
which returns
TRUE if the mouse buttons have been swapped.
See Also