Is it possible to control the CAPS LOCK LED on OS X?
I don't use the CAPS LOCK functionality in OS X, so I disabled the key under the system preferences. Now that key is completely useless to me - ok, I could map the CMD/CTRL/ALT key to that key, but I already got keys for that…
So what I have in mind is to use the LED on the key (I use the recent Apple wireless keyboard) to annouce if I've got mails waiting… something like that. Is it possible to control the LED directly? Controlling it via an objective-c cocoa app is okay, I'll write that app by myself, but until now, I can find anything useful from Apples cocoa documentation.
You can manipulate Mac keyboard LEDs with this..
/*
* keyboard_leds.c
* Manipulate keyboard LEDs (capslock and numlock) programmatically.
*
* gcc -Wall -o keyboard_leds keyboard_leds.c -framework IOKit
* -framework CoreFoundation
*
* Copyright (c) 2007,2008 Amit Singh. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#define PROGNAME "keyboard_leds"
#define PROGVERS "0.1"
#include <stdio.h>
#include <getopt.h>
#include <stdlib.h>
#include <sysexits.h>
#include <mach/mach_error.h>
#include <IOKit/IOCFPlugIn.h>
#include <IOKit/hid/IOHIDLib.h>
#include <IOKit/hid/IOHIDUsageTables.h>
static IOHIDElementCookie capslock_cookie = (IOHIDElementCookie)0;
static IOHIDElementCookie numlock_cookie = (IOHIDElementCookie)0;
static int capslock_value = -1;
static int numlock_value = -1;
void usage(void);
inline void print_errmsg_if_io_err(int expr, char* msg);
inline void print_errmsg_if_err(int expr, char* msg);
io_service_t find_a_keyboard(void);
void find_led_cookies(IOHIDDeviceInterface122** handle);
void create_hid_interface(io_object_t hidDevice,
IOHIDDeviceInterface*** hdi);
int manipulate_led(UInt32 whichLED, UInt32 value);
void
usage(void)
{
fprintf(stderr, "%s (version %s)\n"
"Copyright (c) 2007,2008 Amit Singh. All Rights Reserved.\n"
"Manipulate keyboard LEDs\n\n"
"Usage: %s [OPTIONS...], where OPTIONS is one of the following\n\n"
" -c[1|0], --capslock[=1|=0] get or set (on=1, off=0) caps lock LED\n"
" -h, --help print this help message and exit\n"
" -n[1|0], --numlock[=1|=0] get or set (on=1, off=0) num lock LED\n",
PROGNAME, PROGVERS, PROGNAME);
}
inline void
print_errmsg_if_io_err(int expr, char* msg)
{
IOReturn err = (expr);
if (err != kIOReturnSuccess) {
fprintf(stderr, "*** %s - %s(%x, %d).\n", msg, mach_error_string(err),
err, err & 0xffffff);
fflush(stderr);
exit(EX_OSERR);
}
}
inline void
print_errmsg_if_err(int expr, char* msg)
{
if (expr) {
fprintf(stderr, "*** %s.\n", msg);
fflush(stderr);
exit(EX_OSERR);
}
}
io_service_t
find_a_keyboard(void)
{
io_service_t result = (io_service_t)0;
CFNumberRef usagePageRef = (CFNumberRef)0;
CFNumberRef usageRef = (CFNumberRef)0;
CFMutableDictionaryRef matchingDictRef = (CFMutableDictionaryRef)0;
if (!(matchingDictRef = IOServiceMatching(kIOHIDDeviceKey))) {
return result;
}
UInt32 usagePage = kHIDPage_GenericDesktop;
UInt32 usage = kHIDUsage_GD_Keyboard;
if (!(usagePageRef = CFNumberCreate(kCFAllocatorDefault, kCFNumberIntType,
&usagePage))) {
goto out;
}
if (!(usageRef = CFNumberCreate(kCFAllocatorDefault, kCFNumberIntType,
&usage))) {
goto out;
}
CFDictionarySetValue(matchingDictRef, CFSTR(kIOHIDPrimaryUsagePageKey),
usagePageRef);
CFDictionarySetValue(matchingDictRef, CFSTR(kIOHIDPrimaryUsageKey),
usageRef);
result = IOServiceGetMatchingService(kIOMasterPortDefault, matchingDictRef);
out:
if (usageRef) {
CFRelease(usageRef);
}
if (usagePageRef) {
CFRelease(usagePageRef);
}
return result;
}
void
find_led_cookies(IOHIDDeviceInterface122** handle)
{
IOHIDElementCookie cookie;
CFTypeRef object;
long number;
long usage;
long usagePage;
CFArrayRef elements;
CFDictionaryRef element;
IOReturn result;
if (!handle || !(*handle)) {
return;
}
result = (*handle)->copyMatchingElements(handle, NULL, &elements);
if (result != kIOReturnSuccess) {
fprintf(stderr, "Failed to copy cookies.\n");
exit(1);
}
CFIndex i;
for (i = 0; i < CFArrayGetCount(elements); i++) {
element = CFArrayGetValueAtIndex(elements, i);
object = (CFDictionaryGetValue(element, CFSTR(kIOHIDElementCookieKey)));
if (object == 0 || CFGetTypeID(object) != CFNumberGetTypeID()) {
continue;
}
if (!CFNumberGetValue((CFNumberRef) object, kCFNumberLongType,
&number)) {
continue;
}
cookie = (IOHIDElementCookie)number;
object = CFDictionaryGetValue(element, CFSTR(kIOHIDElementUsageKey));
if (object == 0 || CFGetTypeID(object) != CFNumberGetTypeID()) {
continue;
}
if (!CFNumberGetValue((CFNumberRef)object, kCFNumberLongType,
&number)) {
continue;
}
usage = number;
object = CFDictionaryGetValue(element,CFSTR(kIOHIDElementUsagePageKey));
if (object == 0 || CFGetTypeID(object) != CFNumberGetTypeID()) {
continue;
}
if (!CFNumberGetValue((CFNumberRef)object, kCFNumberLongType,
&number)) {
continue;
}
usagePage = number;
if (usagePage == kHIDPage_LEDs) {
switch (usage) {
case kHIDUsage_LED_NumLock:
numlock_cookie = cookie;
break;
case kHIDUsage_LED_CapsLock:
capslock_cookie = cookie;
break;
default:
break;
}
}
}
return;
}
void
create_hid_interface(io_object_t hidDevice, IOHIDDeviceInterface*** hdi)
{
IOCFPlugInInterface** plugInInterface = NULL;
io_name_t className;
HRESULT plugInResult = S_OK;
SInt32 score = 0;
IOReturn ioReturnValue = kIOReturnSuccess;
ioReturnValue = IOObjectGetClass(hidDevice, className);
print_errmsg_if_io_err(ioReturnValue, "Failed to get class name.");
ioReturnValue = IOCreatePlugInInterfaceForService(
hidDevice, kIOHIDDeviceUserClientTypeID,
kIOCFPlugInInterfaceID, &plugInInterface, &score);
if (ioReturnValue != kIOReturnSuccess) {
return;
}
plugInResult = (*plugInInterface)->QueryInterface(plugInInterface,
CFUUIDGetUUIDBytes(kIOHIDDeviceInterfaceID), (LPVOID)hdi);
print_errmsg_if_err(plugInResult != S_OK,
"Failed to create device interface.\n");
(*plugInInterface)->Release(plugInInterface);
}
int
manipulate_led(UInt32 whichLED, UInt32 value)
{
io_service_t hidService = (io_service_t)0;
io_object_t hidDevice = (io_object_t)0;
IOHIDDeviceInterface **hidDeviceInterface = NULL;
IOReturn ioReturnValue = kIOReturnError;
IOHIDElementCookie theCookie = (IOHIDElementCookie)0;
IOHIDEventStruct theEvent;
if (!(hidService = find_a_keyboard())) {
fprintf(stderr, "No keyboard found.\n");
return ioReturnValue;
}
hidDevice = (io_object_t)hidService;
create_hid_interface(hidDevice, &hidDeviceInterface);
find_led_cookies((IOHIDDeviceInterface122 **)hidDeviceInterface);
ioReturnValue = IOObjectRelease(hidDevice);
if (ioReturnValue != kIOReturnSuccess) {
goto out;
}
ioReturnValue = kIOReturnError;
if (hidDeviceInterface == NULL) {
fprintf(stderr, "Failed to create HID device interface.\n");
return ioReturnValue;
}
if (whichLED == kHIDUsage_LED_NumLock) {
theCookie = numlock_cookie;
} else if (whichLED == kHIDUsage_LED_CapsLock) {
theCookie = capslock_cookie;
}
if (theCookie == 0) {
fprintf(stderr, "Bad or missing LED cookie.\n");
goto out;
}
ioReturnValue = (*hidDeviceInterface)->open(hidDeviceInterface, 0);
if (ioReturnValue != kIOReturnSuccess) {
fprintf(stderr, "Failed to open HID device interface.\n");
goto out;
}
ioReturnValue = (*hidDeviceInterface)->getElementValue(hidDeviceInterface,
theCookie, &theEvent);
if (ioReturnValue != kIOReturnSuccess) {
(void)(*hidDeviceInterface)->close(hidDeviceInterface);
goto out;
}
fprintf(stdout, "%s\n", (theEvent.value) ? "on" : "off");
if (value != -1) {
if (theEvent.value != value) {
theEvent.value = value;
ioReturnValue = (*hidDeviceInterface)->setElementValue(
hidDeviceInterface, theCookie,
&theEvent, 0, 0, 0, 0);
if (ioReturnValue == kIOReturnSuccess) {
fprintf(stdout, "%s\n", (theEvent.value) ? "on" : "off");
}
}
}
ioReturnValue = (*hidDeviceInterface)->close(hidDeviceInterface);
out:
(void)(*hidDeviceInterface)->Release(hidDeviceInterface);
return ioReturnValue;
}
static const char *options = "c::hn::";
static struct option
long_options[] = {
{ "capslock", optional_argument, 0, 'c' },
{ "help", no_argument, 0, 'h' },
{ "numlock", optional_argument, 0, 'n' },
{ 0, 0, 0, 0 },
};
int
main (int argc, char **argv)
{
UInt32 whichLED = (UInt32)0;
int c, ctr = 0;
int target_value = -1;
while ((c = getopt_long(argc, argv, options, long_options, NULL)) != -1) {
switch (c) {
case 0:
break;
case 'c':
ctr++;
whichLED = kHIDUsage_LED_CapsLock;
if (optarg) {
capslock_value = atoi(optarg);
target_value = (capslock_value);
}
break;
case 'h':
usage();
exit(0);
break;
case 'n':
ctr++;
whichLED = kHIDUsage_LED_NumLock;
if (optarg) {
numlock_value = atoi(optarg);
target_value = (numlock_value);
}
break;
default:
usage();
exit(1);
break;
}
}
if (ctr != 1) {
fprintf(stderr, "Missing options or invalid combination of options. "
"Try -h for help.\n");
exit(1);
}
return manipulate_led(whichLED, target_value);
}
To compile and use this script
gcc -Wall -o keyboard_leds keyboard_leds.c \
-framework IOKit -framework CoreFoundation
./keyboard_leds -h
./keyboard_leds -c # query caps lock LED state
./keyboard_leds -c1 # turn caps lock LED on
./keyboard_leds -c0 # turn caps lock LED off
Here's another tool to control keyboard leds under OSX: https://github.com/busyloop/maclight
MacLight lets you control the keyboard-LEDs (capslock, numlock) on your Mac.
One Python example: http://www.psychicorigami.com/2009/03/01/5k-morse-code-app-using-capslock-led/
It is possible. I am trying to find an app that I found years ago, that could toggle the num lock and caps lock LEDs on my old iBook (10.4). Found that while looking today.
Found it.
- http://osxbook.com/book/bonus/chapter10/kbdleds/
- http://googlemac.blogspot.com/2008/04/manipulating-keyboard-leds-through.html
Needs to be compiled though.
Oh, and HID LED test tool – Xcode example :D