How to get Magic Mouse/Trackpad InputValueCallback

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Hello, Can you provide complete example of use IOHIDDevice API's to get input from mouse?

Complete code example would help to identify issue.

USBHIDDevice *currentDevice;

@interface USBHIDDevice() {

IOHIDDeviceRef deviceRef;

} @end

@implementation USBHIDDevice

-(instancetype)initWithDevice:(IOHIDDeviceRef)deviceRef {

self = [super init];
if (self) {
    [self setDeviceRef:deviceRef];
}
return self;

}

-(void)connectHID{

[self openDevice];

}

-(void)disConnectHID {

if(deviceRef){
    [self closeDevice];
}

}

-(IOReturn)openDevice {

if (!deviceRef) {
    return kIOReturnError;
}
currentDevice = self;
IOReturn ioReturn = IOHIDDeviceOpen(deviceRef, kIOHIDOptionsTypeNone);
if ( kIOReturnSuccess == ioReturn ) {
    char *inputbuffer = malloc(64);
    IOHIDDeviceRegisterInputReportCallback(deviceRef, (uint8_t*)inputbuffer, 64, inputCallback, NULL);
    NSDictionary *inputMatchingDict = @{@(kIOHIDElementUsagePageKey): @(0x09), @(kIOHIDElementUsageKey): @(0x02)};
    IOHIDDeviceSetInputValueMatching(deviceRef, (__bridge CFDictionaryRef)inputMatchingDict);
    IOHIDDeviceRegisterInputValueCallback(deviceRef, mouseInputValueCallback, NULL);
}else{
    [self setDeviceRef:NULL];
}
return ioReturn;

}

-(IOReturn)closeDevice {

IOReturn ioReturn = [self checkHIDDevice];
if (kIOReturnSuccess == ioReturn) {
    ioReturn = IOHIDDeviceClose(deviceRef, kIOHIDOptionsTypeNone);
}
[self setDeviceRef:NULL];
return ioReturn;

}

-(IOReturn)checkHIDDevice{

if (!deviceRef) {
    NSLog(@"close devie failed(%x).", kIOReturnNotOpen);
    return kIOReturnNotOpen;
}
return kIOReturnSuccess;

}

-(NSArray *)getHIDReprots {

if (!deviceRef) {
    return nil;
}

NSMutableArray *reports = [[NSMutableArray alloc] init];

CFArrayRef elements;
CFIndex i;

elements = __IOHIDDeviceCopyMatchingInputElements(deviceRef, NULL);

elements = IOHIDDeviceCopyMatchingElements(deviceRef, NULL, kIOHIDOptionsTypeNone);
for (i = 0; i<CFArrayGetCount(elements); i++) {
    const IOHIDElementRef element = (void*)CFArrayGetValueAtIndex(elements, i);
    IOHIDElementType eleType = IOHIDElementGetType(element);
    NSString *eleTypeStr = @"";
    switch (eleType) {
        case kIOHIDElementTypeInput_Misc:
            eleTypeStr = @"kIOHIDElementTypeInput_Misc";
            break;
        case kIOHIDElementTypeInput_Button:
            eleTypeStr = @"kIOHIDElementTypeInput_Button";
            break;
        case kIOHIDElementTypeInput_Axis:
            eleTypeStr = @"kIOHIDElementTypeInput_Axis";
            break;
        case kIOHIDElementTypeInput_ScanCodes:
            eleTypeStr = @"kIOHIDElementTypeInput_ScanCodes";
            break;
        case kIOHIDElementTypeInput_NULL:
            eleTypeStr = @"kIOHIDElementTypeInput_NULL";
            break;
        case kIOHIDElementTypeOutput:
            eleTypeStr = @"kIOHIDElementTypeOutput";
            break;
        case kIOHIDElementTypeFeature:
            eleTypeStr = @"kIOHIDElementTypeFeature";
            break;
        case kIOHIDElementTypeCollection:
            eleTypeStr = @"kIOHIDElementTypeCollection";
            break;
        default:
            break;
    }
    
    uint32_t page = IOHIDElementGetUsagePage(element);
    uint32_t usage = IOHIDElementGetUsage(element);
    uint32_t reportID = IOHIDElementGetReportID(element);
    uint32_t reportSize = IOHIDElementGetReportSize(element);
    uint32_t reportCount = IOHIDElementGetReportCount(element);
    
    NSString *elementStr = [[NSString alloc] initWithFormat:@" reportID:%d, reportSize:%d, type:%@, UsagePage:%d, usage:%d, reportCount:%d\n\n",reportID, reportSize, eleTypeStr, page, usage, reportCount];
    
    [reports addObject:elementStr];
}
return reports;

}

CFArrayRef __IOHIDDeviceCopyMatchingInputElements(IOHIDDeviceRef device, CFArrayRef multiple) {

CFMutableArrayRef       inputElements   = NULL;
CFArrayRef              elements        = NULL;
CFIndex                 index, count;

// Grab the matching multiple.  If one has not already been specified,
// fallback to the default
if ( multiple ) {
    CFRetain(multiple);
} else {
    uint32_t inputTypes[] = { kIOHIDElementTypeInput_Misc, kIOHIDElementTypeInput_Button, kIOHIDElementTypeInput_Axis, kIOHIDElementTypeInput_ScanCodes};
    count = sizeof(inputTypes) / sizeof(uint32_t);
    CFDictionaryRef matching[count];
    bzero(matching, sizeof(CFDictionaryRef) * count);
    
    CFStringRef key = CFSTR(kIOHIDElementTypeKey);
    for ( index=0; index<count; index++ ) {
        CFNumberRef number = CFNumberCreate(kCFAllocatorDefault, kCFNumberIntType, &inputTypes[index]);
        matching[index] = CFDictionaryCreate(kCFAllocatorDefault,
                                             (const void **)&key,
                                             (const void **)&number,
                                             1,
                                             &kCFCopyStringDictionaryKeyCallBacks,
                                             &kCFTypeDictionaryValueCallBacks);
        CFRelease(number);
    }
    
    multiple = CFArrayCreate(kCFAllocatorDefault, (const void **)matching, count, &kCFTypeArrayCallBacks);
    for ( index=0; index<count; index++ )
        CFRelease(matching[index]);
}

if ( !multiple )
    return NULL;
    
count = CFArrayGetCount( multiple );

for ( index=0; index<count; index++) {
    elements = IOHIDDeviceCopyMatchingElements( device,
                                                CFArrayGetValueAtIndex(multiple, index),
                                                0);
    if ( !elements )
        continue;
        
    if ( !inputElements )
        inputElements = CFArrayCreateMutableCopy(   kCFAllocatorDefault,
                                                    0,
                                                    elements);
    else
        CFArrayAppendArray( inputElements,
                            elements,
                            CFRangeMake(0, CFArrayGetCount(elements)));
 
    CFRelease(elements);
}

CFRelease(multiple);
return inputElements;

}

static void inputCallback(void* context, IOReturn result, void* sender, IOHIDReportType type, uint32_t reportID, uint8_t *report, CFIndex reportLength) {

[currentDevice sendMessageWithDelegate:report length:reportLength];

}

static void mouseInputValueCallback(void *context, IOReturn result, void *sender, IOHIDValueRef value) { NSLog(@"handle input value"); }

-(void)sendMessageWithDelegate:(uint8_t*)recvData length:(CFIndex)reportLength{

}

Need to provide execution context for callback with IOHIDDeviceSetDispatchQueue or IOHIDDeviceUnscheduleFromRunLoop. Also consider setting up callbacks first: IOHIDDeviceRegisterInputReportCallback(deviceRef, (uint8_t*)inputbuffer, 64, inputCallback, NULL); NSDictionary *inputMatchingDict = @{@(kIOHIDElementUsagePageKey): @(0x09), @(kIOHIDElementUsageKey): @(0x02)}; IOHIDDeviceSetInputValueMatching(deviceRef, (__bridge CFDictionaryRef)inputMatchingDict); IOHIDDeviceRegisterInputValueCallback(deviceRef, mouseInputValueCallback, NULL); before calling IOHIDDeviceOpen