Still haven't received your answer in the comments, but since that might also help other people in the future I decided to answer anyway.
With the IOKit you can detect the keyboard has a device, and get the key press events like device events. I've used that to detect joystick events, but it should work with keyboards has well. I assume that the modifications that I made are enough and should work, however my Xcode is updating now, so I wasn't able to test it yet.
KeyboardWatcher.h File:
#import <Foundation/Foundation.h>
#import <IOKit/hid/IOHIDManager.h>
#import <IOKit/hid/IOHIDKeys.h>
@interface KeyboardWatcher : NSObject{
IOHIDManagerRef HIDManager;
}
@property (nonatomic) int keysPressedCount;
+(instancetype)sharedWatcher;
-(void)startWatching;
-(void)stopWatching;
@end
KeyboardWatcher.m File:
#import "KeyboardWatcher.h"
@implementation KeyboardWatcher
static KeyboardWatcher *_sharedWatcher;
+(instancetype)sharedWatcher {
@synchronized([self class]) {
if (!_sharedWatcher){
_sharedWatcher = [[KeyboardWatcher alloc] init];
}
return _sharedWatcher;
}
return nil;
}
-(instancetype)init {
self = [super init];
if (self){
self.keysPressedCount = 0;
}
return self;
}
-(void)startWatching {
[self watchDevicesOfType:kHIDUsage_GD_Keyboard];
}
-(void)watchDevicesOfType:(UInt32)deviceType {
// Create an HID Manager
HIDManager = IOHIDManagerCreate(kCFAllocatorDefault, kIOHIDOptionsTypeNone);
// Create a Matching Dictionary
CFMutableDictionaryRef matchDict = CFDictionaryCreateMutable(kCFAllocatorDefault, 2, &kCFTypeDictionaryKeyCallBacks,
&kCFTypeDictionaryValueCallBacks);
// That will make the app just return the computer keyboards
CFDictionarySetValue(matchDict, CFSTR(kIOHIDPrimaryUsageKey), CFNumberCreate(kCFAllocatorDefault, kCFNumberIntType, &deviceType));
// Register the Matching Dictionary to the HID Manager
IOHIDManagerSetDeviceMatching(HIDManager, matchDict);
// Register the HID Manager on our app’s run loop
IOHIDManagerScheduleWithRunLoop(HIDManager, CFRunLoopGetMain(), kCFRunLoopDefaultMode);
// Open the HID Manager
IOReturn IOReturn = IOHIDManagerOpen(HIDManager, kIOHIDOptionsTypeNone);
// Register input calls to Handle_DeviceEventCallback function
IOHIDManagerRegisterInputValueCallback(HIDManager, Handle_DeviceEventCallback, nil);
if (IOReturn) NSLog(@"IOHIDManagerOpen failed.");
}
-(void)stopWatching {
HIDManager = NULL;
}
static void Handle_DeviceEventCallback (void *inContext, IOReturn inResult, void *inSender, IOHIDValueRef value){
IOHIDElementRef element = IOHIDValueGetElement(value); // Keyboard pressed key
uint32_t uniqueIdentifier = IOHIDElementGetCookie(element); // Unique ID of key
int elementValue = (int)IOHIDValueGetIntegerValue(value); // Actual state of key (1=pressed)
NSLog(@"Unique ID = %u; Value = %d", uniqueIdentifier, elementValue);
if (elementValue == 1) KeyboardWatcher.sharedWatcher.keysPressedCount++;
}
@end
In case you want to identify which unique ID is which key, you can use these enums (instead of importing Carbon you can just create a CGKeyboardMapping.h file and paste them there):
https://stackoverflow.com/a/16125341/4370893
At last, in order to use it, you just need to do that to start watching for keyboard events:
[[KeyboardWatcher sharedWatcher] startWatching];
Get the key pressed count with that:
[[KeyboardWatcher sharedWatcher] keysPressedCount];
And that to stop:
[[KeyboardWatcher sharedWatcher] stopWatching];
These were my references to write my original joystick code:
As soon as the update finishes I will test the code and inform if it's working or not for sure.
EDIT: Just tested and it's working. Don't forget to add the IOKit framework to the project.
