Trying to catch keyboard events

Catching Hardware Keyboard Events (Cmd Shift Alt Ctrl)

// Created by Guillermo Enriquez on 09/10/2012.
// Copyright 2012 nacho4d. All rights reserved.

int main(int argc, char *argv[]) {
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    int retVal = UIApplicationMain(argc, argv, @"Application", @"AppDelegate");
    [pool drain];
    return retVal;
}

@interface Application : UIApplication
@end
@implementation Application

// Calculation of offsets for traversing GSEventRef:
// Count the size of types inside CGEventRecord struct
// https://github.com/kennytm/iphone-private-frameworks/blob/master/GraphicsServices/GSEvent.h

// typedef struct GSEventRecord {
//        GSEventType type; // 0x8 //2
//        GSEventSubType subtype;    // 0xC //3
//        CGPoint location;     // 0x10 //4
//        CGPoint windowLocation;    // 0x18 //6
//        int windowContextId;    // 0x20 //8
//        uint64_t timestamp;    // 0x24, from mach_absolute_time //9
//        GSWindowRef window;    // 0x2C //
//        GSEventFlags flags;    // 0x30 //12
//        unsigned senderPID;    // 0x34 //13
//        CFIndex infoSize; // 0x38 //14
// } GSEventRecord;

// typedef struct GSEventKey {
//        GSEvent _super;
//        UniChar keycode, characterIgnoringModifier, character;    // 0x38, 0x3A, 0x3C // 15 and start of 16
//        short characterSet;        // 0x3E // end of 16
//        Boolean isKeyRepeating;    // 0x40 // start of 17
// } GSEventKey;

#define GSEVENT_TYPE 2
//#define GSEVENT_SUBTYPE 3
//#define GSEVENT_LOCATION 4
//#define GSEVENT_WINLOCATION 6
//#define GSEVENT_WINCONTEXTID 8
//#define GSEVENT_TIMESTAMP 9
//#define GSEVENT_WINREF 11
#define GSEVENT_FLAGS 12
//#define GSEVENT_SENDERPID 13
//#define GSEVENT_INFOSIZE 14

#define GSEVENTKEY_KEYCODE_CHARIGNORINGMOD 15
//#define GSEVENTKEY_CHARSET_CHARSET 16
//#define GSEVENTKEY_ISKEYREPEATING 17 // ??

#define GSEVENT_TYPE_KEYDOWN 10
#define GSEVENT_TYPE_KEYUP 11

NSString *const UIEventGSEventKeyUpNotification = @"UIEventGSEventKeyUpNotification";

- (void)sendEvent:(UIEvent *)event
{
    [super sendEvent:event];

    if ([event respondsToSelector:@selector(_gsEvent)]) {
        // Hardware Key events are of kind UIInternalEvent which are a wrapper of GSEventRef which is wrapper of GSEventRecord
        int *eventMemory = (int *)[event performSelector:@selector(_gsEvent)];
        if (eventMemory) {
            
            int eventType = eventMemory[GSEVENT_TYPE];
            NSLog(@"event type = %d", eventType);
            if (eventType == GSEVENT_TYPE_KEYUP) {
                
                // Since the event type is key up we can assume is a GSEventKey struct
                // Get flags from GSEvent
                int eventFlags = eventMemory[GSEVENT_FLAGS];
                if (eventFlags) { 
                    NSLog(@"flags %8X", eventFlags);
                    // Only post notifications when Shift, Ctrl, Cmd or Alt key were pressed.

                    // Get keycode from GSEventKey
                    int tmp = eventMemory[15];
                    UniChar *keycode = (UniChar *)&tmp; // Cast to silent warning
                    //tmp = (tmp & 0xFF00);
                    //tmp = tmp >> 16;
                    //UniChar keycode = tmp;
                    //tmp = eventMemory[16];
                    //tmp = (tmp & 0x00FF);
                    //tmp = tmp << 16;
                    //UniChar keycode = tmp;
                    NSLog(@"keycode %d", keycode[0]);
                    //printf("Shift Ctrl Alt Cmd %d %d %d %d\n ", (eventFlags&(1<<17))?1:0, (eventFlags&(1<<18))?1:0, (eventFlags&(1<<19))?1:0, (eventFlags&(1<<20))?1:0 );
                    
                    NSDictionary *userInfo = [[NSDictionary alloc] initWithObjectsAndKeys:[NSNumber numberWithShort:keycode[0]], @"keycode", [NSNumber numberWithInt:eventFlags], @"eventFlags", nil];
                    [[NSNotificationCenter defaultCenter] postNotificationName:UIEventGSEventKeyUpNotification object:nil userInfo:userInfo];

                    /* 
                     Some Keycodes found
                     ===================

                     Alphabet
                     a = 4
                     b = 5
                     c = ...
                     z = 29
                     
                     Numbers
                     1 = 30
                     2 = 31
                     3 = ...
                     9 = 38
                     
                     Arrows
                     Right = 79
                     Left = 80
                     Down = 81
                     Up = 82
                     
                     Flags found (Differ from Kenny's header)
                     ========================================
                     
                     Cmd = 1 << 17
                     Shift = 1 << 18
                     Ctrl = 1 << 19
                     Alt = 1 << 20
                     
                     */
                }
            }
        }
    }
}
@end

Catching Hardware Keyboard Events (Cmd, Shift, Alt, Ctrl)

int main(int argc, char *argv[]) {
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    int retVal = UIApplicationMain(argc, argv, @"Application", @"AppDelegate");
    [pool drain];
    return retVal;
}

@interface Application : UIApplication
@end
@implementation Application

// Calculation of offsets for traversing GSEventRef:
// Count the size of types inside CGEventRecord struct. Just for Reference:
// https://github.com/kennytm/iphone-private-frameworks/blob/master/GraphicsServices/GSEvent.h

// typedef struct GSEventRecord {
//    GSEventType type; // 0x8
//    GSEventSubType subtype;    // 0xC
//    CGPoint location;     // 0x10
//    CGPoint windowLocation;    // 0x18
//    int windowContextId;    // 0x20
//    uint64_t timestamp;    // 0x24, from mach_absolute_time
//    GSWindowRef window;    // 0x2C
//    GSEventFlags flags;    // 0x30
//    unsigned senderPID;    // 0x34
//    CFIndex infoSize; // 0x38
//} GSEventRecord;

#define GS_EVENT_TYPE_OFFSET 2

// fields length (1 : 4 bytes)
#define GS_EVENT_TYPE_LEN 1
#define GS_EVENT_SUBTYPE_LEN 1
#define GS_EVENT_LOCATION_LEN 2
#define GS_EVENT_WINLOCATION_LEN 2
#define GS_EVENT_WINCONTEXTID_LEN 1
#define GS_EVENT_TIMESTAMP_LEN 4
#define GS_EVENT_WINREF_LEN 1
//#define GS_EVENT_FLAGS_LEN 1
//#define GS_EVENT_SENDERPID_LEN 1
//#define GS_EVENT_INFOSIZE_LEN 1

- (void)sendEvent:(UIEvent *)anEvent
{
    [super sendEvent:anEvent];
    return;// Disable below code because so far I couldn't find key event flags (Shift, Cmd, Alt, Ctrl)

    // Send notification if is a keyboard event
    if ([anEvent respondsToSelector:@selector(_gsEvent)]) {
        // Hardware Key events are of kind UIInternalEvent which are a wrapper of GSEventRef which is wrapper of GSEventRecord
        int *eventMemory = (int *)[anEvent performSelector:@selector(_gsEvent)];
        if (eventMemory) {

            int eventType = eventMemory[GS_EVENT_TYPE_OFFSET];
            NSLog(@"event type = %d", eventType); // keydown:11, keyup:12

            int flagsOffset = GS_EVENT_TYPE_OFFSET + GS_EVENT_TYPE_LEN + GS_EVENT_SUBTYPE_LEN + GS_EVENT_LOCATION_LEN + GS_EVENT_WINLOCATION_LEN + GS_EVENT_WINCONTEXTID_LEN + GS_EVENT_TIMESTAMP_LEN + GS_EVENT_WINREF_LEN;
            
           // Apparently above offset calculation is only for iOS4, in iOS5 GSEvent.h is somehow changed and below code does not work

           int eventFlags = eventMemory[flagsOffset];
           printf("%8X ", eventFlags);
           printf("Shift Ctrl Alt Cmd %d %d %d %d\n ", (eventFlags&(1<<17))?1:0, (eventFlags&(1<<18))?1:0, (eventFlags&(1<<19))?1:0, (eventFlags&(1<<20))?1:0 );

          // Now do something with the flags :)
        }
    }
}

@end

Experimenting with this, on my iPad (3rd gen, iOS 6.1.3) + Apple BT keyboard, the modifier flags are like so. Wonder if this differs per version of iOS and/or hardware:

1 << 16 // cmd
1 << 17 // shift
1 << 19 // option
1 << 20 // ctrl