Ideas for future versions of DirectInput keyboard support are presented.
Currently, keyboards are supported only in passive (non-exclusive) mode.
Adding support for exclusive mode on the system keyboard
(GUID_SysKeyboard)
is extremely easy on Windows NT, and
a bit tricky on Windows 9x.
On Windows NT, all that would need to be done is to have the
CEm_LL_KbdHook function return 1 without calling
CallNexthookEx in the situation where the keyboard
has been acquired exclusively. This will prevent Windows
applications (including the current application) from seeing
keyboard activity, while not preventing the secure attention
sequence (Ctrl+Alt+Del) from operating properly.
For Windows 9x, the change would be similar, but more annoying.
The DIKBD_Filter_Keyboard_Input
function would return carry set rather than clear if the
keyboard is captured. Steal the basic idea from the
dimouse.asm file, which already does this for
mouse events. (I.e., handle the DIKBD_Capture
notification, set a flag in the instance structure,
and check the flag in the filter procedure.)
It's actually not quite that easy, because Windows 9x does not have a security manager. The low-level keyboard filter procedure would also need to track the virtual shift state and detect that the user has typed Ctrl+Alt+Del. Under such conditions, the filter would have to force-unacquire the device, then turn around and re-inject the Ctrl+Alt+Del sequence (now with the filter disabled) so the system can see it again.
Note also that
CKbd_SetCooperativeLevel would need to be changed
to understand which modes support exclusive access and which do not.
This is a common request from game developers, because the Windows Logo Key sits right next to two extremely popular game keys - Ctrl and Alt. Accidentally pressing the Windows Logo key causes the Start Menu to open, which in turn causes the application to lose focus and possible even lose its display surfaces.
This can be solved as a restricted (and much easier)
form of exclusive keyboard access. Again, on Windows NT,
we would merely check if the incoming key is
VK_LWIN or VK_RWIN; if so, then return 1
immediately without chaining.
On Windows 9x, the filter procedure would check for a scan code of
E0/5B or E0/5C (or their release counterparts E0/DB and E0/DC);
if so, convert the 5B or 5C (or DB or DC) to a harmless key like 00.
DirectX 5.0 DDK , Microsoft Corporation.
DirectX 5.0 SDK , Microsoft Corporation.