keyremap.c

/* keyremap.c
 *
 * features:
 * 1. map lower enter to forward delete key - useful for macbooks
 *    (works only when secure event input is not activated,
 *    which happens very rarely, e.g. when password fields are focused)
 * 2. send enter key event when right command key is released
 *    without any other key pressed while it was down
 *
 * by Bert Mu"nnich, January 2009
 * Based on http://www.osxbook.com/book/bonus/chapter2/alterkeys/
 * so the credits go to Amit Singh
 * 
 * Compile it using the following cmdline:
 *   gcc -framework ApplicationServices -O3 -o keyremap keyremap.c
 *
 * Tested on Mac OS X 10.6.1
 */

#define debug(...) if (debugMsgsEnabled) printf(__VA_ARGS__)

#define RIGHT_CMD_DOWN 1048848
#define MODIFIER_UP 256

#include <ApplicationServices/ApplicationServices.h>

const CGKeyCode ENTER = (CGKeyCode) 76;
const CGKeyCode FWDDEL = (CGKeyCode) 117;
const CGKeyCode RIGHT_CMD = (CGKeyCode) 54;

static bool sendEnter = false;
static bool debugMsgsEnabled = false;

const char *progname = "";

CGEventRef myCGEventCallback(CGEventTapProxy proxy, CGEventType type, CGEventRef event, void *refcon) {
  CGKeyCode keycode = (CGKeyCode) CGEventGetIntegerValueField(event, kCGKeyboardEventKeycode);
  CGEventFlags modifiers = CGEventGetFlags(event);

	debug("Type: %i Modifiers: %i Keycode: %i\n", type, (int) modifiers, keycode);

	if (keycode == RIGHT_CMD) {
		if (modifiers == RIGHT_CMD_DOWN) {
			sendEnter = true;
		} else if (modifiers == MODIFIER_UP && sendEnter) {
			debug("right cmd released with no other key pressed -> send enter key event\n");
			sendEnter = false;

			// we had to get a new CGEventRef every time because creating a
			// global one causes a bus error inside CGEventCreateKeyboardEvent
			CGEventRef enterKey = CGEventCreateKeyboardEvent(NULL, ENTER, true);
			CGEventSetFlags(enterKey, (CGEventFlags) 256);

			// press the enter key...
			CGEventSetType(enterKey, kCGEventKeyDown);
			CGEventTapPostEvent(proxy, enterKey);

			// ... and release it
			CGEventSetType(enterKey, kCGEventKeyUp);
			CGEventTapPostEvent(proxy, enterKey);

			CFRelease(enterKey);
		}
	} else if (sendEnter) {
		debug("another key pressed while right cmd down -> don't send enter key event\n");
		sendEnter = false;
	}

	if (keycode == ENTER) {
		debug("change enter to fwd delete\n");
		CGEventSetIntegerValueField(event, kCGKeyboardEventKeycode, FWDDEL);
	}

  return event;
}

int main(int argc, char **argv) {
	if (argc > 1) {
		debugMsgsEnabled = true;
	}

	progname = argv[0];

  CFMachPortRef eventTap;
  CFRunLoopSourceRef runLoopSource;

	CGEventMask eventMask = CGEventMaskBit(kCGEventFlagsChanged) | CGEventMaskBit(kCGEventKeyDown) | CGEventMaskBit(kCGEventKeyUp); 
  eventTap = CGEventTapCreate(kCGSessionEventTap, kCGHeadInsertEventTap, 0, eventMask, myCGEventCallback, NULL);

  if (!eventTap) {
    fprintf(stderr, "Failed to create event tap!\n");
    exit(1);
  }

  runLoopSource = CFMachPortCreateRunLoopSource(NULL, eventTap, 0);
	CFRelease(eventTap);
  CFRunLoopAddSource(CFRunLoopGetCurrent(), runLoopSource, kCFRunLoopCommonModes);
	CFRelease(runLoopSource);
  CFRunLoopRun();

  exit(0);
}