 |
| Copyright © 1997-1999
Mark Russinovich |
Last Updated November 22, 1999, Version 2.0
|
| Introduction |
Ctrl2cap is a kernel-mode
device driver that filters the system's keyboard class driver in order to
convert caps-lock characters into control characters. People like myself that
migrated to NT from UNIX are used to having the control key located where the
caps-lock key is on the standard PC keyboard, so a utility like this is
essential for our editing well-being. Ctrl2cap works on NT 4.0 and Win2K. See Ctrl2cap for Windows 9x for a version that works on
Windows 95/98.
|
| Installation and Use |
Install Ctrl2cap running the
command "ctrl2cap /install" from the directory into which you've
unzipped the Ctrl2cap files. To uninstall type "ctrl2cap
/uninstall". |
| Building Ctrl2cap |
Ctrl2cap requires ntddkbd.h
from the ddk\src\input\inc directory, so you must first copy that file to the
ctrl2cap directory. To build a standard NT 4 driver type "buildnt4"
and to build a Win2K WDM driver type "buildnt5". Output files are
placed in the \release subdirectory. |
How Ctrl2cap Works
|
On NT 4 Ctrlcap is actually
quite trivial. It simply attaches itself to the keyboard class driver so that
it will catch keyboard read requests. For each request, it posts an I/O
completion callback, at which point it takes a peek at the scancode that is
being returned. If it happens to be a caps-lock, ctrl2cap changes it into a
left-control.
On Win2K Ctrl2cap is a WDM filter
driver that layers in the keyboard class device's stack above the keyboard
class device. This is in contrast to the Win2K DDK's kbfiltr example that
layers itself between the i8042 port device and the keyboard class device. I
chose to layer on top of the keyboard class device for several reasons:
- It means that the Ctrl2cap
IRP_MJ_READ interception and manipulation code is shared between the NT 4 and
Win2K versions .
- I don't need to supply an INF
file and have the user go through the Device Manager to install Ctrl2cap - I
simply modify the appropriate Registry value (the keyboard class devices's
HKLM\Syste ²ŸƒrrentControlSet\Control\Class UpperFilters value). See the source
code to Ctrl2cap.exe for more information.
The disadvantage of my approach is
(and this an advantage or disadvantage depending on your point of view):
- Because I don't install with an
INF file via the Device Manager, the user is not warned that the Ctrl2cap
driver file is not digitally signed by Microsoft.
In this particular case I felt that
the advantages outweigh the disadvantages. However, before you model a Win2K
keyboard filter on Ctrl2cap I strongly suggest that you study the kbfiltr
example from the Win2K DDK. Kbfiltr's interception point in the key input
sequence makes it very easy for kbfiltr to inject keystrokes into the input
stream, something that would be more difficult using the Ctrl2cap source
base.
|
More Information
|
For more information on writing
filter drivers (drivers that attach themselves to other drivers so that they
can see their input and/or output), here are sources to check out:
- The Windows NT and Windows 2000
DDK sample \src\storage\filter\diskperf
- The Windows 2000 DDK sample
\src\input\kbfiltr
- "Examining the Windows NT
File System," by Mark Russinovich and Bryce Cogswell, Dr. Dobb's Journal,
February 1997 the accompanying
file system filter driver, Filemon.
|
Download Ctrl2cap (6KB)
Download
Ctrl2cap Plus Source (65KB)
|
 |