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Overview |
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Group |
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Quick Info
Windows NT
| Yes
| Win95
| Yes
| Win32s
| Yes
| Import Library
| -
| Header File
| winuser.h
| Unicode
| No
| Platform Notes
| None
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WM_SYSKEYUP
The WM_SYSKEYUP 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.
WM_SYSKEYUP
nVirtKey = (int) wParam; // virtual-key code
lKeyData = lParam; // key data
Parameters
nVirtKey
Value of wParam. Specifies the virtual-key code of the key being released.
lKeyData
Value of 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:
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. The repeat count is
always one for a WM_SYSKEYUP message.
| 1623
| Specifies the scan code. The value depends on the original equipment
manufacturer (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. The value is 1 if
it is an extended key; otherwise, it is 0.
| 2528
| Reserved; do not use.
| 29
| Specifies the context code. The value is 1 if the ALT key is down while the key is released; it is 0 if the WM_SYSKEYDOWN message
is posted to the active window because no window has the keyboard focus.
| 30
| Specifies the previous key state. The value is always 1 for a WM_SYSKEYUP
message.
| 31
| Specifies the transition state. The value is always 1 for a WM_SYSKEYUP
message.
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Return Values
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 system character-key message. This allows 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
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See Also
DefWindowProc, TranslateAccelerator, WM_SYSCOMMAND, WM_SYSKEYDOWN
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