WM_KEYDOWN (Compact 2013)

3/28/2014

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.

Syntax

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.
  16-23	Specifies the scan code. This value depends on the original equipment manufacturer.
  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 Value

An application should return zero if it processes this message.

• Default Action
  If the F10 key is pressed, the DefWindowProc function sets an internal flag. When DefWindowProc receives the WM_KEYUP message, the function checks whether the internal flag is set and, if so, sends a WM_SYSCOMMAND message to the top-level window. The wParam parameter 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 lKeyData parameter.

Requirements

See Also

Reference

Keyboard Messages
DefWindowProc
WM_CHAR
WM_KEYUP
WM_SYSCOMMAND