The WM_KEYUP message is posted to the window with the keyboard focus when a nonsystem key is released. A nonsystem key is a key that is pressed when the ALT key is not pressed, or a keyboard key that is pressed when a window has the keyboard focus.
WM_KEYUP
nVirtKey = (int) wParam; // virtual-key code
lKeyData = lParam; // key data
Parameters
nVirtKey
Value of wParam. Specifies the virtual-key code of the nonsystem key.
lKeyData
Value of lParam. Specifies the repeat count, scan code, extended-key flag, context code, previous key-state flag, and transition-state flag, as shown in the following table:
| Value | Description |
| 0-15 | Specifies the repeat count. The value is the number of times the keystroke is repeated as a result of the user holding down the key. The repeat count is always one for a WM_KEYUP message. |
| 16-23 | Specifies the scan code. The value depends on the original equipment manufacturer (OEM). |
| 24 | Specifies whether the key is an extended key, such as the right-hand ALT and CTRL keys that appear on an enhanced 101- or 102-key keyboard. The value is 1 if it is an extended key; otherwise, it is 0. |
| 25-28 | Reserved; do not use. |
| 29 | Specifies the context code. The value is always 0 for a WM_KEYUP message. |
| 30 | Specifies the previous key state. The value is always 1 for a WM_KEYUP message. |
| 31 | Specifies the transition state. The value is always 1 for a WM_KEYUP message. |
Return Values
An application should return zero if it processes this message.
Default Action
The DefWindowProc function sends a WM_SYSCOMMAND message to the top-level window if the F10 key or the ALT key was released. The wParam parameter of the message is set to SC_KEYMENU.
Remarks
For enhanced 101- and 102-key keyboards, extended keys are the right ALT and CTRL keys on the main section of the keyboard; the INS, DEL, HOME, END, PAGE UP, PAGE DOWN and arrow keys in the clusters to the left of the numeric keypad; and the divide (/) and ENTER keys in the numeric keypad. Other keyboards may support the extended-key bit in the lKeyData parameter.
See Also