This 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; lKeyData = lParam;
Specifies the virtual-key code of the nonsystem key.
Specifies the repeat count, context code, previous key-state flag, and transition-state flag, as shown in the following table.
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.
Specifies the scan code. This value depends on the original equipment manufacturer.
Specifies the context code. The value is 1 if the ALT key is held down while the key is pressed; otherwise, the value is 0.
Specifies the previous key state. The value is 1 if the key is down before the message is sent, or it is 0 if the key is up.
Specifies the transition state. The value is 1 if the key is being released, or it is 0 if the key is being pressed.
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.