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. The least significant bit is not valid in Windows Embedded CE, and should be ignored. GetAsyncKeyStatereturns the current key state even if a window in another thread or process currently has the keyboard focus.

You can use the VK_LBUTTON virtual-key code constant to determine whether the stylus tip is touching the screen or not.

The GetAsyncKeyStatefunction 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, regardless of whether it is 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

	Copy Code
GetSystemMetrics(SM_SWAPBUTTON)

which returns TRUE if the mouse buttons have been swapped.

You can use the virtual-key code constants VK_SHIFT, VK_CONTROL, and VK_MENU as values for the vKeyparameter. This gives the state of the SHIFT, CTRL, or ALT keys without distinguishing between left and right.

You can use the following virtual-key code constants as values for vKeyto distinguish between the left and right instances of those keys.

These left- and right-distinguishing constants are only available when you call the GetAsyncKeyState, GetKeyState, and MapVirtualKeyfunctions.