WM_KEYDOWN/WM_KEYUP
Syntax
WM_KEYDOWN WPARAM wParam LPARAM lParam;Parameters
wParam
Specifies the virtual-key code of the nonsystem key.
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.0-15 Specifies the repeat count for the current message. The value is the number of times the keystroke is autorepeated as a result of the user holding down the key. If the keystroke is held long enough, multiple messages are sent. However, the repeat count is not cumulative. 16-23 Specifies the scan code. The value depends on the 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. T he 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_KEYDOWN message. 30 Specifies the previous key state. The value is 1 if the key is down before the message is sent, or it is zero if the key is up. 31 Specifies the transition state. The value is always zero for a WM_KEYDOWN message.Return Value
An application should return zero if it processes this message.
Syntax
WM_KEYUP WPARAM wParam LPARAM lParam;Parameters
wParam
Specifies the virtual-key code of the nonsystem key.
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.0-15 Specifies the repeat count for the current message. The value is the number of times the keystroke is autorepeated 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 OEM. 24 Specifies whether the key is an extended key, such as the right-hand AL 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 ValueAn application should return zero if it processes this message.