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WM_SYSKEYUP (Compact 2013)

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3/28/2014

This message is posted to the window with the keyboard focus when the user releases a key that was pressed while the ALT key was held down. It also occurs when no window currently has the keyboard focus; in this case, the WM_SYSKEYUP message is sent to the active window. The window that receives the message can distinguish between these two contexts by checking the context code in the lKeyData parameter.

Syntax

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

Parameters

  • nVirtKey
    Specifies the virtual-key code of the key being released.

  • 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 Value

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

When the context code is zero, the message can be passed to the TranslateAccelerator function, which will handle it as though it were a normal key message instead of a character-key message. This enables accelerator keys to be used with the active window even if the active window does not have the keyboard focus.

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.

For non-U.S. enhanced 102-key keyboards, the right ALT key is handled as a CTRL+ALT key. The following table shows the sequence of messages that result when the user presses and releases this key.

Message

Virtual-key code

WM_KEYDOWN

VK_CONTROL

WM_KEYDOWN

VK_MENU

WM_KEYUP

VK_CONTROL

WM_SYSKEYUP

VK_MENU

Requirements

Header

winuser.h

See Also

Reference

Keyboard Messages
DefWindowProc
TranslateAccelerator
WM_SYSKEYDOWN