WM_KEYDOWN

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This message is posted to the window with the keyboard focus when a nonsystem key is pressed. A nonsystem key is a key that is pressed when the ALT key is not pressed.

WM_KEYDOWN
nVirtKey= 
(int)
wParam; 
lKeyData= 
lParam;

Parameters

nVirtKey

Specifies the virtual-key code of the nonsystem key.

lKeyData

Specifies the repeat count, 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.
29	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.
30	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.
31	Specifies the transition state. The value is 1 if the key is being released, or it is 0 if the key is being pressed.

Return Values

An application should return zero if it processes this message.

Default Action

If the F10 key is pressed, the DefWindowProcfunction sets an internal flag. When DefWindowProcreceives the WM_KEYUPmessage, the function checks whether the internal flag is set and, if so, sends a WM_SYSCOMMANDmessage to the top-level window. The wParamparameter of the message is set to SC_KEYMENU.

Remarks

Because of the autorepeat feature, more than one WM_KEYDOWN message may be posted before a WM_KEYUP message is posted. The previous key state (bit 30) can be used to determine whether the WM_KEYDOWN message indicates the first down transition or a repeated down transition.

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 lKeyDataparameter.

Requirements

Runs on	Versions	Defined in	Include	Link to
Windows CE OS	1.0 and later	Winuser.h

Note This API is part of the complete Windows CE OS package as provided by Microsoft. The functionality of a particular platform is determined by the original equipment manufacturer (OEM) and some devices may not support this API.