|
Overview |
|
|
|
Group |
|
|
|
Quick Info
Windows NT
| Yes
| Win95
| Yes
| Win32s
| Yes
| Import Library
| -
| Header File
| winuser.h
| Unicode
| No
| Platform Notes
| None
|
|
|
WM_SYSKEYDOWN
The WM_SYSKEYDOWN message is posted to the window with the keyboard focus when
the user holds down the ALT key and then presses another key. It also occurs when no window currently has
the keyboard focus; in this case, the WM_SYSKEYDOWN 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_SYSKEYDOWN
nVirtKey = (int) wParam; // virtual-key code
lKeyData = lParam; // key data
Parameters
nVirtKey
Value of wParam. Specifies the virtual-key code of the key being pressed.
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.
| 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 pressed; 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 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 always 0 for a WM_SYSKEYDOWN
message.
|
Return Values
An application should return zero if it processes this message.
Default Action
The DefWindowProc function examines the given key and generates a WM_SYSCOMMAND message if the key is either TAB or ENTER.
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.
Because of automatic repeat, more than one WM_SYSKEYDOWN message may occur
before a WM_SYSKEYUP message is sent. The previous key state (bit 30) can be used
to determine whether the WM_SYSKEYDOWN message indicates the first down
transition or a repeated down transition.
For enhanced 101- and 102-key keyboards, enhanced 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 lParam parameter.
See Also
DefWindowProc, TranslateAccelerator, WM_SYSCOMMAND, WM_SYSKEYUP
Related Links
Software for Delphi and C++ Builder developers
Software for Visual Studio .NET developers
Software for Visual Basic 6 developers
Delphi Tips&Tricks
MegaDetailed.NET
TMS Scripter Studio Pro components for Delphi/C++Builder
More Online Helps
Win32 Multimedia Programmer's Reference (mmedia.hlp)
OLE Programmer's Reference (ole.hlp)
Microsoft Windows Pen API Programmer's Reference (penapi.hlp)
Microsoft Windows Sockets 2 Reference (sock2.hlp)
Microsoft Windows Telephony API (TAPI) Programmer's Reference (tapi.hlp)
Unix Manual Pages
|
