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c++.windows.32-bits - GetAsyncKeyState

reply "Heinz-Peter Nuettgens" <hnuettgens t-online.de> writes:
Is there anyone, who has an idea why in Windows 98
GetAsyncKeyState doesn't work with VK_LSHIFT, VK_RSHIFT,
VK_LMENU, VK_RMENU, VK_LCONTROL and VK_RCONTROL ?

It works well with VK_SHIFT, VK_CONTROL, VK_MENU and
VK_LWIN, VK_RWIN and VK_APPS.

Windows2000 does it, as I expect, but 98 won't.

But I would like to distinguish between holding down right or left key.
I didn't find a statement in the knowledgebase that it shouldn't work
with Windows98.
May 24 2002
next sibling parent Jan Knepper <jan smartsoft.cc> writes:
Oh, this should like one of those beautiful things M$ does...
I have no idea why it has to be different between W98 and W2K, but it would
not be the first thing that is different.
Jan



Heinz-Peter Nuettgens wrote:


 Is there anyone, who has an idea why in Windows 98
 GetAsyncKeyState doesn't work with VK_LSHIFT, VK_RSHIFT,
 VK_LMENU, VK_RMENU, VK_LCONTROL and VK_RCONTROL ?

 It works well with VK_SHIFT, VK_CONTROL, VK_MENU and
 VK_LWIN, VK_RWIN and VK_APPS.

 Windows2000 does it, as I expect, but 98 won't.

 But I would like to distinguish between holding down right or left key.
 I didn't find a statement in the knowledgebase that it shouldn't work
 with Windows98.
May 24 2002
prev sibling parent Jan Knepper <jan smartsoft.cc> writes:
Actually, according to MSDN there is a difference between NT/2K/XP and
others:

GetAsyncKeyState
The GetAsyncKeyState function determines whether a key is up or down at the
time the function is called, and whether the key was pressed after a
previous call to GetAsyncKeyState.

SHORT GetAsyncKeyState(
  int vKey   // virtual-key code
);
Parameters
vKey
[in] Specifies one of 256 possible virtual-key codes. For more information,
see Virtual-Key Codes.
Windows NT/2000/XP: You can use left- and right-distinguishing constants to
specify certain keys. See the Remarks section for further information.

Return Values
If the function succeeds, the return value specifies whether the key was
pressed since the last call to GetAsyncKeyState, and whether the key is
currently up or down. If the most significant bit is set, the key is down,
and if the least significant bit is set, the key was pressed after the
previous call to GetAsyncKeyState. However, you should not rely on this
last behavior; for more information, see the Remarks.

Windows NT/2000/XP: The return value is zero for the following cases:

The current desktop is not the active desktop
The foreground thread belongs to another process and the desktop does not
allow the hook or the journal record.
Windows 95/98/Me: The return value is the global asynchronous key state for
each virtual key. The system does not check which thread has the keyboard
focus.

Windows 95/98/Me: Windows 95 does not support the left- and
right-distinguishing constants. If you call GetAsyncKeyState with these
constants, the return value is zero.

Remarks
The GetAsyncKeyState function works with mouse buttons. However, it checks
on the state of the physical mouse buttons, not on the logical mouse
buttons that the physical buttons are mapped to. For example, the call
GetAsyncKeyState(VK_LBUTTON) always returns the state of the left physical
mouse button, regardless of whether it is mapped to the left or right
logical mouse button. You can determine the system's current mapping of
physical mouse buttons to logical mouse buttons by calling

GetSystemMetrics(SM_SWAPBUTTON)
which returns TRUE if the mouse buttons have been swapped.

Although the least significant bit of the return value indicates whether
the key has been pressed since the last query, due to the pre-emptive
multitasking nature of Windows, another application can call
GetAsyncKeyState and receive the "recently pressed" bit instead of your
application. The behavior of the least significant bit of the return value
is retained strictly for compatibility with 16-bit Windows applications
(which are non-preemptive) and should not be relied upon.

You can use the virtual-key code constants VK_SHIFT, VK_CONTROL, and
VK_MENU as values for the vKey parameter. This gives the state of the
SHIFT, CTRL, or ALT keys without distinguishing between left and right.

Windows NT/2000/XP: You can use the following virtual-key code constants as
values for vKey to distinguish between the left and right instances of
those keys.

Code Meaning
VK_LSHIFT VK_RSHIFT
VK_LCONTROL VK_RCONTROL
VK_LMENU VK_RMENU


These left- and right-distinguishing constants are only available when you
call the GetKeyboardState, SetKeyboardState, GetAsyncKeyState, GetKeyState,
and MapVirtualKey functions.

Requirements
  Windows NT/2000/XP: Included in Windows NT 3.1 and later.
  Windows 95/98/Me: Included in Windows 95 and later.
  Header: Declared in Winuser.h; include Windows.h.
  Library: Use User32.lib.
May 24 2002