Mega Code Archive
Keysdisable
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> I believe Jim Burns has a solution for this...
Cute! And I belive you and I traded ideas on issues like this for a short
while so you should have everything I have baby!
It's been a while since I played with these issues including disabling
Alt-Tab, Alt-Esc, the Logo keys, etc.
On Win98 you can disable ALL Fast Task Switching (FTS) with the following,
procedure EnableFastTaskSwitching(Enable : boolean = True);
begin
// Logical twist here. If Enable is False, we must use True to disable,
// If Enable is True, we must use False to enable
SystemParametersInfo(SPI_SCREENSAVERRUNNING, cardinal(NOT Enable), nil,
0);
end;
This is a blanket-trick however and it kills it everything, including HotKey
sequences.
To get more specific control, the only way I've found is a system keyboard
hook where you test specific keys and key combinations. But again, there
are some differences there even with respect to Win98 and WinNT/2K.
More importantly WinNT/2K has a low-level Keyboard hook (WH_KEYBOARD_LL)
that will get you inside the input queue before the standard hook. This
allows you to prevent just about everything individually except
Ctrl-Alt-Del. On Win98, since the hook isn't available, this means you
can't prevent the use of the Logo keys this way, although you will catch
their use.
With repect to this low-level hook we have the following to help test,
const LLKHF_EXTENDED = $00000001;
const LLKHF_INJECTED = $00000010;
const LLKHF_ALTDOWN = $00000020;
const LLKHF_UP = $00000080;
These along with the structure,
type
pKBDLLHookStruct = ^TKBDLLHookStruct;
{$EXTERNALSYM tagKBDLLHOOKSTRUCT}
tagKBDLLHOOKSTRUCT = packed record
vkCode : DWORD;
scanCode : DWORD;
flags : DWORD;
time : DWORD;
dwExtraInfo : DWORD;
end;
TKBDLLHookStruct = tagKBDLLHOOKSTRUCT;
{$EXTERNALSYM KBDLLHOOKSTRUCT}
KBDLLHOOKSTRUCT = tagKBDLLHOOKSTRUCT;
are not defined in the standard Delphi units so you'll have to add them
yourself.
Inside your low-level keyboard hook procedure you can do something simple
like,
if (pkbhs^.vkCode = VK_CONTROL) OR
(pkbhs^.vkCode = VK_ESCAPE) then begin
Result := 1;
end;
But you'll notice this will kill ALL use of Ctrl AND Esc. Ctrl-Esc then has
it's own interesting problems. The problem here is how to detect only a
Ctrl-Esc combination. Given the consts you could test for a Alt-Esc
combination simply like,
if (pkbhs^.vkCode = VK_ESCAPE) AND
(pkbhs^.flags = LLKHF_ALTDOWN) then begin
Result := 1;
end;
That's easy to understand, but there is no, LLKHF_CTRLDOWN as one might
expect. Could it be,
if (pkbhs^.vkCode = VK_ESCAPE) AND
(pkbhs^.flags = LLKHF_EXTENDED) then begin
Result := 1;
end;
I don't know. I've not tried. And I've not found a detailed explaination
of these constants. By their naming, my guess is this shouldn't work, but
who knows? Anyone else? It's worth a try.
That's pretty much as far as I got on the matter. A solution? Is there
such a thing with Windows? :) Maybe someone else has some specific details
on the holes in my solution or other ideas, and between us all we can patch
together a picture of all our options with respect to controlling the use,
individually, in select groups, or across the board, of these specialized
keys and key combos on both Win98 AND WinNT/2k.
Is that too much to ask? :)
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Jim Burns jimburns@technologydynamics.com
Technology Dynamics http://www.technologydynamics.com
Pearland, Texas 281 485-0410 / UIN #1845000
USA http://www.brainbench.com/transcript.jsp?pid=96029
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"Delphi where we can; the API where it counts!"
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