Simulate/Toggle CAPS LOCK programatically in OS X

Question

I have seen many post on this topic. But haven\'t found a clear answer anywhere.

Is there a way to toggle CAPS LOCK in Objective-C or C code? I am not looking for a

Answer 1

I got this working, after a long struggle.

Invoke the method given below twice. Once for up event and another for down event. For example for simulating CAPS A, we need to do the following.

[self handleKeyEventWithCapsOn:0 andKeyDown:NO];
[self handleKeyEventWithCapsOn:0 andKeyDown:YES];

0 is the keycode for 'a'.

- (void) handleKeyEventWithCapsOn:(int) keyCode andKeyDown:(BOOL)keyDown
{
    if(keyDown)
    {
        CGEventRef eventDown;
        eventDown = CGEventCreateKeyboardEvent(NULL, (CGKeyCode)keyCode, true);
        CGEventSetFlags(eventDown, kCGEventFlagMaskShift);
        CGEventPost(kCGSessionEventTap, eventDown);
        CFRelease(eventDown);
    }
    else
    {
        CGEventRef eventUp;
        eventUp = CGEventCreateKeyboardEvent(NULL, (CGKeyCode)keyCode, false);
        CGEventSetFlags(eventUp, kCGEventFlagMaskShift);
        CGEventPost(kCGSessionEventTap, eventUp);

        // SHIFT Up Event
        CGEventRef eShiftUp = CGEventCreateKeyboardEvent(NULL, (CGKeyCode)56, false);
        CGEventPost(kCGSessionEventTap, eShiftUp);
        CFRelease(eventUp);
        CFRelease(eShiftUp);
    }
}

Answer 2

var ioConnect: io_connect_t = .init(0)
let ioService = IOServiceGetMatchingService(kIOMasterPortDefault, IOServiceMatching(kIOHIDSystemClass))
IOServiceOpen(ioService, mach_task_self_, UInt32(kIOHIDParamConnectType), &ioConnect)

var modifierLockState = false
IOHIDGetModifierLockState(ioConnect, Int32(kIOHIDCapsLockState), &modifierLockState) 

modifierLockState.toggle()
IOHIDSetModifierLockState(ioConnect, Int32(kIOHIDCapsLockState), modifierLockState)

IOServiceClose(ioConnect)