src/joystick/darwin/SDL_sysjoystick.c

/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2018 Sam Lantinga <slouken@libsdl.org>

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
*/
#include "../../SDL_internal.h"

#ifdef SDL_JOYSTICK_IOKIT

#include "SDL_events.h"
#include "SDL_joystick.h"
#include "../SDL_sysjoystick.h"
#include "../SDL_joystick_c.h"
#include "SDL_sysjoystick_c.h"
#include "../hidapi/SDL_hidapijoystick_c.h"
#include "../../haptic/darwin/SDL_syshaptic_c.h"    /* For haptic hot plugging */


#define SDL_JOYSTICK_RUNLOOP_MODE CFSTR("SDLJoystick")

#define CONVERT_MAGNITUDE(x)    (((x)*10000) / 0x7FFF)

/* The base object of the HID Manager API */
static IOHIDManagerRef hidman = NULL;

/* Linked list of all available devices */
static recDevice *gpDeviceList = NULL;

void FreeRumbleEffectData(FFEFFECT *effect)
{
    if (!effect) {
        return;
    }
    SDL_free(effect->rgdwAxes);
    SDL_free(effect->rglDirection);
    SDL_free(effect->lpvTypeSpecificParams);
    SDL_free(effect);
}

FFEFFECT *CreateRumbleEffectData(Sint16 magnitude, Uint32 duration_ms)
{
    FFEFFECT *effect;
    FFPERIODIC *periodic;

    /* Create the effect */
    effect = (FFEFFECT *)SDL_calloc(1, sizeof(*effect));
    if (!effect) {
        return NULL;
    }
    effect->dwSize = sizeof(*effect);
    effect->dwGain = 10000;
    effect->dwFlags = FFEFF_OBJECTOFFSETS;
    effect->dwDuration = duration_ms * 1000; /* In microseconds. */
    effect->dwTriggerButton = FFEB_NOTRIGGER;

    effect->cAxes = 2;
    effect->rgdwAxes = (DWORD *)SDL_calloc(effect->cAxes, sizeof(DWORD));
    if (!effect->rgdwAxes) {
        FreeRumbleEffectData(effect);
        return NULL;
    }

    effect->rglDirection = (LONG *)SDL_calloc(effect->cAxes, sizeof(LONG));
    if (!effect->rglDirection) {
        FreeRumbleEffectData(effect);
        return NULL;
    }
    effect->dwFlags |= FFEFF_CARTESIAN;

    periodic = (FFPERIODIC *)SDL_calloc(1, sizeof(*periodic));
    if (!periodic) {
        FreeRumbleEffectData(effect);
        return NULL;
    }
    periodic->dwMagnitude = CONVERT_MAGNITUDE(magnitude);
    periodic->dwPeriod = 1000000;

    effect->cbTypeSpecificParams = sizeof(*periodic);
    effect->lpvTypeSpecificParams = periodic;

    return effect;
}

static recDevice *GetDeviceForIndex(int device_index)
{
    recDevice *device = gpDeviceList;
    while (device) {
        if (!device->removed) {
            if (device_index == 0)
                break;

            --device_index;
        }
        device = device->pNext;
    }
    return device;
}

static void
FreeElementList(recElement *pElement)
{
    while (pElement) {
        recElement *pElementNext = pElement->pNext;
        SDL_free(pElement);
        pElement = pElementNext;
    }
}

static recDevice *
FreeDevice(recDevice *removeDevice)
{
    recDevice *pDeviceNext = NULL;
    if (removeDevice) {
        if (removeDevice->deviceRef) {
            IOHIDDeviceUnscheduleFromRunLoop(removeDevice->deviceRef, CFRunLoopGetCurrent(), SDL_JOYSTICK_RUNLOOP_MODE);
            removeDevice->deviceRef = NULL;
        }

        /* save next device prior to disposing of this device */
        pDeviceNext = removeDevice->pNext;

        if ( gpDeviceList == removeDevice ) {
            gpDeviceList = pDeviceNext;
        } else {
            recDevice *device = gpDeviceList;
            while (device->pNext != removeDevice) {
                device = device->pNext;
            }
            device->pNext = pDeviceNext;
        }
        removeDevice->pNext = NULL;

        /* free element lists */
        FreeElementList(removeDevice->firstAxis);
        FreeElementList(removeDevice->firstButton);
        FreeElementList(removeDevice->firstHat);

        SDL_free(removeDevice);
    }
    return pDeviceNext;
}

static SDL_bool
GetHIDElementState(recDevice *pDevice, recElement *pElement, SInt32 *pValue)
{
    SInt32 value = 0;
    int returnValue = SDL_FALSE;

    if (pDevice && pElement) {
        IOHIDValueRef valueRef;
        if (IOHIDDeviceGetValue(pDevice->deviceRef, pElement->elementRef, &valueRef) == kIOReturnSuccess) {
            value = (SInt32) IOHIDValueGetIntegerValue(valueRef);

            /* record min and max for auto calibration */
            if (value < pElement->minReport) {
                pElement->minReport = value;
            }
            if (value > pElement->maxReport) {
                pElement->maxReport = value;
            }
            *pValue = value;

            returnValue = SDL_TRUE;
        }
    }
    return returnValue;
}

static SDL_bool
GetHIDScaledCalibratedState(recDevice * pDevice, recElement * pElement, SInt32 min, SInt32 max, SInt32 *pValue)
{
    const float deviceScale = max - min;
    const float readScale = pElement->maxReport - pElement->minReport;
    int returnValue = SDL_FALSE;
    if (GetHIDElementState(pDevice, pElement, pValue))
    {
        if (readScale == 0) {
            returnValue = SDL_TRUE;           /* no scaling at all */
        }
        else
        {
            *pValue = ((*pValue - pElement->minReport) * deviceScale / readScale) + min;
            returnValue = SDL_TRUE;
        }
    } 
    return returnValue;
}

static void
JoystickDeviceWasRemovedCallback(void *ctx, IOReturn result, void *sender)
{
    recDevice *device = (recDevice *) ctx;
    device->removed = SDL_TRUE;
    device->deviceRef = NULL; // deviceRef was invalidated due to the remove
    if (device->ffeffect_ref) {
        FFDeviceReleaseEffect(device->ffdevice, device->ffeffect_ref);
        device->ffeffect_ref = NULL;
    }
    if (device->ffeffect) {
        FreeRumbleEffectData(device->ffeffect);
        device->ffeffect = NULL;
    }
    if (device->ffdevice) {
        FFReleaseDevice(device->ffdevice);
        device->ffdevice = NULL;
        device->ff_initialized = SDL_FALSE;
    }
#if SDL_HAPTIC_IOKIT
    MacHaptic_MaybeRemoveDevice(device->ffservice);
#endif

    SDL_PrivateJoystickRemoved(device->instance_id);
}


static void AddHIDElement(const void *value, void *parameter);

/* Call AddHIDElement() on all elements in an array of IOHIDElementRefs */
static void
AddHIDElements(CFArrayRef array, recDevice *pDevice)
{
    const CFRange range = { 0, CFArrayGetCount(array) };
    CFArrayApplyFunction(array, range, AddHIDElement, pDevice);
}

static SDL_bool
ElementAlreadyAdded(const IOHIDElementCookie cookie, const recElement *listitem) {
    while (listitem) {
        if (listitem->cookie == cookie) {
            return SDL_TRUE;
        }
        listitem = listitem->pNext;
    }
    return SDL_FALSE;
}

/* See if we care about this HID element, and if so, note it in our recDevice. */
static void
AddHIDElement(const void *value, void *parameter)
{
    recDevice *pDevice = (recDevice *) parameter;
    IOHIDElementRef refElement = (IOHIDElementRef) value;
    const CFTypeID elementTypeID = refElement ? CFGetTypeID(refElement) : 0;

    if (refElement && (elementTypeID == IOHIDElementGetTypeID())) {
        const IOHIDElementCookie cookie = IOHIDElementGetCookie(refElement);
        const uint32_t usagePage = IOHIDElementGetUsagePage(refElement);
        const uint32_t usage = IOHIDElementGetUsage(refElement);
        recElement *element = NULL;
        recElement **headElement = NULL;

        /* look at types of interest */
        switch (IOHIDElementGetType(refElement)) {
            case kIOHIDElementTypeInput_Misc:
            case kIOHIDElementTypeInput_Button:
            case kIOHIDElementTypeInput_Axis: {
                switch (usagePage) {    /* only interested in kHIDPage_GenericDesktop and kHIDPage_Button */
                    case kHIDPage_GenericDesktop:
                        switch (usage) {
                            case kHIDUsage_GD_X:
                            case kHIDUsage_GD_Y:
                            case kHIDUsage_GD_Z:
                            case kHIDUsage_GD_Rx:
                            case kHIDUsage_GD_Ry:
                            case kHIDUsage_GD_Rz:
                            case kHIDUsage_GD_Slider:
                            case kHIDUsage_GD_Dial:
                            case kHIDUsage_GD_Wheel:
                                if (!ElementAlreadyAdded(cookie, pDevice->firstAxis)) {
                                    element = (recElement *) SDL_calloc(1, sizeof (recElement));
                                    if (element) {
                                        pDevice->axes++;
                                        headElement = &(pDevice->firstAxis);
                                    }
                                }
                                break;

                            case kHIDUsage_GD_Hatswitch:
                                if (!ElementAlreadyAdded(cookie, pDevice->firstHat)) {
                                    element = (recElement *) SDL_calloc(1, sizeof (recElement));
                                    if (element) {
                                        pDevice->hats++;
                                        headElement = &(pDevice->firstHat);
                                    }
                                }
                                break;
                            case kHIDUsage_GD_DPadUp:
                            case kHIDUsage_GD_DPadDown:
                            case kHIDUsage_GD_DPadRight:
                            case kHIDUsage_GD_DPadLeft:
                            case kHIDUsage_GD_Start:
                            case kHIDUsage_GD_Select:
                            case kHIDUsage_GD_SystemMainMenu:
                                if (!ElementAlreadyAdded(cookie, pDevice->firstButton)) {
                                    element = (recElement *) SDL_calloc(1, sizeof (recElement));
                                    if (element) {
                                        pDevice->buttons++;
                                        headElement = &(pDevice->firstButton);
                                    }
                                }
                                break;
                        }
                        break;

                    case kHIDPage_Simulation:
                        switch (usage) {
                            case kHIDUsage_Sim_Rudder:
                            case kHIDUsage_Sim_Throttle:
                            case kHIDUsage_Sim_Accelerator:
                            case kHIDUsage_Sim_Brake:
                                if (!ElementAlreadyAdded(cookie, pDevice->firstAxis)) {
                                    element = (recElement *) SDL_calloc(1, sizeof (recElement));
                                    if (element) {
                                        pDevice->axes++;
                                        headElement = &(pDevice->firstAxis);
                                    }
                                }
                                break;

                            default:
                                break;
                        }
                        break;

                    case kHIDPage_Button:
                    case kHIDPage_Consumer: /* e.g. 'pause' button on Steelseries MFi gamepads. */
                        if (!ElementAlreadyAdded(cookie, pDevice->firstButton)) {
                            element = (recElement *) SDL_calloc(1, sizeof (recElement));
                            if (element) {
                                pDevice->buttons++;
                                headElement = &(pDevice->firstButton);
                            }
                        }
                        break;

                    default:
                        break;
                }
            }
            break;

            case kIOHIDElementTypeCollection: {
                CFArrayRef array = IOHIDElementGetChildren(refElement);
                if (array) {
                    AddHIDElements(array, pDevice);
                }
            }
            break;

            default:
                break;
        }

        if (element && headElement) {       /* add to list */
            recElement *elementPrevious = NULL;
            recElement *elementCurrent = *headElement;
            while (elementCurrent && usage >= elementCurrent->usage) {
                elementPrevious = elementCurrent;
                elementCurrent = elementCurrent->pNext;
            }
            if (elementPrevious) {
                elementPrevious->pNext = element;
            } else {
                *headElement = element;
            }

            element->elementRef = refElement;
            element->usagePage = usagePage;
            element->usage = usage;
            element->pNext = elementCurrent;

            element->minReport = element->min = (SInt32) IOHIDElementGetLogicalMin(refElement);
            element->maxReport = element->max = (SInt32) IOHIDElementGetLogicalMax(refElement);
            element->cookie = IOHIDElementGetCookie(refElement);

            pDevice->elements++;
        }
    }
}

static SDL_bool
GetDeviceInfo(IOHIDDeviceRef hidDevice, recDevice *pDevice)
{
    Sint32 vendor = 0;
    Sint32 product = 0;
    Sint32 version = 0;
    CFTypeRef refCF = NULL;
    CFArrayRef array = NULL;
    Uint16 *guid16 = (Uint16 *)pDevice->guid.data;

    /* get usage page and usage */
    refCF = IOHIDDeviceGetProperty(hidDevice, CFSTR(kIOHIDPrimaryUsagePageKey));
    if (refCF) {
        CFNumberGetValue(refCF, kCFNumberSInt32Type, &pDevice->usagePage);
    }
    if (pDevice->usagePage != kHIDPage_GenericDesktop) {
        return SDL_FALSE; /* Filter device list to non-keyboard/mouse stuff */
    }

    refCF = IOHIDDeviceGetProperty(hidDevice, CFSTR(kIOHIDPrimaryUsageKey));
    if (refCF) {
        CFNumberGetValue(refCF, kCFNumberSInt32Type, &pDevice->usage);
    }

    if ((pDevice->usage != kHIDUsage_GD_Joystick &&
         pDevice->usage != kHIDUsage_GD_GamePad &&
         pDevice->usage != kHIDUsage_GD_MultiAxisController)) {
        return SDL_FALSE; /* Filter device list to non-keyboard/mouse stuff */
    }

    pDevice->deviceRef = hidDevice;

    /* get device name */
    refCF = IOHIDDeviceGetProperty(hidDevice, CFSTR(kIOHIDProductKey));
    if (!refCF) {
        /* Maybe we can't get "AwesomeJoystick2000", but we can get "Logitech"? */
        refCF = IOHIDDeviceGetProperty(hidDevice, CFSTR(kIOHIDManufacturerKey));
    }
    if ((!refCF) || (!CFStringGetCString(refCF, pDevice->product, sizeof (pDevice->product), kCFStringEncodingUTF8))) {
        SDL_strlcpy(pDevice->product, "Unidentified joystick", sizeof (pDevice->product));
    }

    refCF = IOHIDDeviceGetProperty(hidDevice, CFSTR(kIOHIDVendorIDKey));
    if (refCF) {
        CFNumberGetValue(refCF, kCFNumberSInt32Type, &vendor);
    }

    refCF = IOHIDDeviceGetProperty(hidDevice, CFSTR(kIOHIDProductIDKey));
    if (refCF) {
        CFNumberGetValue(refCF, kCFNumberSInt32Type, &product);
    }

    refCF = IOHIDDeviceGetProperty(hidDevice, CFSTR(kIOHIDVersionNumberKey));
    if (refCF) {
        CFNumberGetValue(refCF, kCFNumberSInt32Type, &version);
    }

#ifdef SDL_JOYSTICK_HIDAPI
    if (HIDAPI_IsDevicePresent(vendor, product, version)) {
        /* The HIDAPI driver is taking care of this device */
        return 0;
    }
#endif

    SDL_memset(pDevice->guid.data, 0, sizeof(pDevice->guid.data));

    if (vendor && product) {
        *guid16++ = SDL_SwapLE16(SDL_HARDWARE_BUS_USB);
        *guid16++ = 0;
        *guid16++ = SDL_SwapLE16((Uint16)vendor);
        *guid16++ = 0;
        *guid16++ = SDL_SwapLE16((Uint16)product);
        *guid16++ = 0;
        *guid16++ = SDL_SwapLE16((Uint16)version);
        *guid16++ = 0;
    } else {
        *guid16++ = SDL_SwapLE16(SDL_HARDWARE_BUS_BLUETOOTH);
        *guid16++ = 0;
        SDL_strlcpy((char*)guid16, pDevice->product, sizeof(pDevice->guid.data) - 4);
    }

    array = IOHIDDeviceCopyMatchingElements(hidDevice, NULL, kIOHIDOptionsTypeNone);
    if (array) {
        AddHIDElements(array, pDevice);
        CFRelease(array);
    }

    return SDL_TRUE;
}

static SDL_bool
JoystickAlreadyKnown(IOHIDDeviceRef ioHIDDeviceObject)
{
    recDevice *i;
    for (i = gpDeviceList; i != NULL; i = i->pNext) {
        if (i->deviceRef == ioHIDDeviceObject) {
            return SDL_TRUE;
        }
    }
    return SDL_FALSE;
}


static void
JoystickDeviceWasAddedCallback(void *ctx, IOReturn res, void *sender, IOHIDDeviceRef ioHIDDeviceObject)
{
    recDevice *device;
    int device_index = 0;
    io_service_t ioservice;

    if (res != kIOReturnSuccess) {
        return;
    }

    if (JoystickAlreadyKnown(ioHIDDeviceObject)) {
        return;  /* IOKit sent us a duplicate. */
    }

    device = (recDevice *) SDL_calloc(1, sizeof(recDevice));
    if (!device) {
        SDL_OutOfMemory();
        return;
    }

    if (!GetDeviceInfo(ioHIDDeviceObject, device)) {
        SDL_free(device);
        return;   /* not a device we care about, probably. */
    }

    if (SDL_ShouldIgnoreJoystick(device->product, device->guid)) {
        SDL_free(device);
        return;
    }

    /* Get notified when this device is disconnected. */
    IOHIDDeviceRegisterRemovalCallback(ioHIDDeviceObject, JoystickDeviceWasRemovedCallback, device);
    IOHIDDeviceScheduleWithRunLoop(ioHIDDeviceObject, CFRunLoopGetCurrent(), SDL_JOYSTICK_RUNLOOP_MODE);

    /* Allocate an instance ID for this device */
    device->instance_id = SDL_GetNextJoystickInstanceID();

    /* We have to do some storage of the io_service_t for SDL_HapticOpenFromJoystick */
    ioservice = IOHIDDeviceGetService(ioHIDDeviceObject);
    if ((ioservice) && (FFIsForceFeedback(ioservice) == FF_OK)) {
        device->ffservice = ioservice;
#if SDL_HAPTIC_IOKIT
        MacHaptic_MaybeAddDevice(ioservice);
#endif
    }

    /* Add device to the end of the list */
    if ( !gpDeviceList ) {
        gpDeviceList = device;
    } else {
        recDevice *curdevice;

        curdevice = gpDeviceList;
        while ( curdevice->pNext ) {
            ++device_index;
            curdevice = curdevice->pNext;
        }
        curdevice->pNext = device;
        ++device_index;  /* bump by one since we counted by pNext. */
    }

    SDL_PrivateJoystickAdded(device->instance_id);
}

static SDL_bool
ConfigHIDManager(CFArrayRef matchingArray)
{
    CFRunLoopRef runloop = CFRunLoopGetCurrent();

    if (IOHIDManagerOpen(hidman, kIOHIDOptionsTypeNone) != kIOReturnSuccess) {
        return SDL_FALSE;
    }

    IOHIDManagerSetDeviceMatchingMultiple(hidman, matchingArray);
    IOHIDManagerRegisterDeviceMatchingCallback(hidman, JoystickDeviceWasAddedCallback, NULL);
    IOHIDManagerScheduleWithRunLoop(hidman, runloop, SDL_JOYSTICK_RUNLOOP_MODE);

    while (CFRunLoopRunInMode(SDL_JOYSTICK_RUNLOOP_MODE,0,TRUE) == kCFRunLoopRunHandledSource) {
        /* no-op. Callback fires once per existing device. */
    }

    /* future hotplug events will come through SDL_JOYSTICK_RUNLOOP_MODE now. */

    return SDL_TRUE;  /* good to go. */
}


static CFDictionaryRef
CreateHIDDeviceMatchDictionary(const UInt32 page, const UInt32 usage, int *okay)
{
    CFDictionaryRef retval = NULL;
    CFNumberRef pageNumRef = CFNumberCreate(kCFAllocatorDefault, kCFNumberIntType, &page);
    CFNumberRef usageNumRef = CFNumberCreate(kCFAllocatorDefault, kCFNumberIntType, &usage);
    const void *keys[2] = { (void *) CFSTR(kIOHIDDeviceUsagePageKey), (void *) CFSTR(kIOHIDDeviceUsageKey) };
    const void *vals[2] = { (void *) pageNumRef, (void *) usageNumRef };

    if (pageNumRef && usageNumRef) {
        retval = CFDictionaryCreate(kCFAllocatorDefault, keys, vals, 2, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
    }

    if (pageNumRef) {
        CFRelease(pageNumRef);
    }
    if (usageNumRef) {
        CFRelease(usageNumRef);
    }

    if (!retval) {
        *okay = 0;
    }

    return retval;
}

static SDL_bool
CreateHIDManager(void)
{
    SDL_bool retval = SDL_FALSE;
    int okay = 1;
    const void *vals[] = {
        (void *) CreateHIDDeviceMatchDictionary(kHIDPage_GenericDesktop, kHIDUsage_GD_Joystick, &okay),
        (void *) CreateHIDDeviceMatchDictionary(kHIDPage_GenericDesktop, kHIDUsage_GD_GamePad, &okay),
        (void *) CreateHIDDeviceMatchDictionary(kHIDPage_GenericDesktop, kHIDUsage_GD_MultiAxisController, &okay),
    };
    const size_t numElements = SDL_arraysize(vals);
    CFArrayRef array = okay ? CFArrayCreate(kCFAllocatorDefault, vals, numElements, &kCFTypeArrayCallBacks) : NULL;
    size_t i;

    for (i = 0; i < numElements; i++) {
        if (vals[i]) {
            CFRelease((CFTypeRef) vals[i]);
        }
    }

    if (array) {
        hidman = IOHIDManagerCreate(kCFAllocatorDefault, kIOHIDOptionsTypeNone);
        if (hidman != NULL) {
            retval = ConfigHIDManager(array);
        }
        CFRelease(array);
    }

    return retval;
}


static int
DARWIN_JoystickInit(void)
{
    if (gpDeviceList) {
        return SDL_SetError("Joystick: Device list already inited.");
    }

    if (!CreateHIDManager()) {
        return SDL_SetError("Joystick: Couldn't initialize HID Manager");
    }

    return 0;
}

static int
DARWIN_JoystickGetCount(void)
{
    recDevice *device = gpDeviceList;
    int nJoySticks = 0;

    while (device) {
        if (!device->removed) {
            nJoySticks++;
        }
        device = device->pNext;
    }

    return nJoySticks;
}

static void
DARWIN_JoystickDetect(void)
{
    recDevice *device = gpDeviceList;
    while (device) {
        if (device->removed) {
            device = FreeDevice(device);
        } else {
            device = device->pNext;
        }
    }

    /* run this after the checks above so we don't set device->removed and delete the device before
       DARWIN_JoystickUpdate can run to clean up the SDL_Joystick object that owns this device */
    while (CFRunLoopRunInMode(SDL_JOYSTICK_RUNLOOP_MODE,0,TRUE) == kCFRunLoopRunHandledSource) {
        /* no-op. Pending callbacks will fire in CFRunLoopRunInMode(). */
    }
}

/* Function to get the device-dependent name of a joystick */
const char *
DARWIN_JoystickGetDeviceName(int device_index)
{
    recDevice *device = GetDeviceForIndex(device_index);
    return device ? device->product : "UNKNOWN";
}

static int
DARWIN_JoystickGetDevicePlayerIndex(int device_index)
{
    return -1;
}

static SDL_JoystickGUID
DARWIN_JoystickGetDeviceGUID( int device_index )
{
    recDevice *device = GetDeviceForIndex(device_index);
    SDL_JoystickGUID guid;
    if (device) {
        guid = device->guid;
    } else {
        SDL_zero(guid);
    }
    return guid;
}

static SDL_JoystickID
DARWIN_JoystickGetDeviceInstanceID(int device_index)
{
    recDevice *device = GetDeviceForIndex(device_index);
    return device ? device->instance_id : 0;
}

static int
DARWIN_JoystickOpen(SDL_Joystick * joystick, int device_index)
{
    recDevice *device = GetDeviceForIndex(device_index);

    joystick->instance_id = device->instance_id;
    joystick->hwdata = device;
    joystick->name = device->product;

    joystick->naxes = device->axes;
    joystick->nhats = device->hats;
    joystick->nballs = 0;
    joystick->nbuttons = device->buttons;
    return 0;
}

/*
 * Like strerror but for force feedback errors.
 */
static const char *
FFStrError(unsigned int err)
{
    switch (err) {
    case FFERR_DEVICEFULL:
        return "device full";
    /* This should be valid, but for some reason isn't defined... */
    /* case FFERR_DEVICENOTREG:
        return "device not registered"; */
    case FFERR_DEVICEPAUSED:
        return "device paused";
    case FFERR_DEVICERELEASED:
        return "device released";
    case FFERR_EFFECTPLAYING:
        return "effect playing";
    case FFERR_EFFECTTYPEMISMATCH:
        return "effect type mismatch";
    case FFERR_EFFECTTYPENOTSUPPORTED:
        return "effect type not supported";
    case FFERR_GENERIC:
        return "undetermined error";
    case FFERR_HASEFFECTS:
        return "device has effects";
    case FFERR_INCOMPLETEEFFECT:
        return "incomplete effect";
    case FFERR_INTERNAL:
        return "internal fault";
    case FFERR_INVALIDDOWNLOADID:
        return "invalid download id";
    case FFERR_INVALIDPARAM:
        return "invalid parameter";
    case FFERR_MOREDATA:
        return "more data";
    case FFERR_NOINTERFACE:
        return "interface not supported";
    case FFERR_NOTDOWNLOADED:
        return "effect is not downloaded";
    case FFERR_NOTINITIALIZED:
        return "object has not been initialized";
    case FFERR_OUTOFMEMORY:
        return "out of memory";
    case FFERR_UNPLUGGED:
        return "device is unplugged";
    case FFERR_UNSUPPORTED:
        return "function call unsupported";
    case FFERR_UNSUPPORTEDAXIS:
        return "axis unsupported";

    default:
        return "unknown error";
    }
}

static int
DARWIN_JoystickInitRumble(recDevice *device, Sint16 magnitude, Uint32 duration_ms)
{
    HRESULT result;

    if (!device->ffdevice) {
        result = FFCreateDevice(device->ffservice, &device->ffdevice);
        if (result != FF_OK) {
            return SDL_SetError("Unable to create force feedback device from service: %s", FFStrError(result));
        }
    }

    /* Reset and then enable actuators */
    result = FFDeviceSendForceFeedbackCommand(device->ffdevice, FFSFFC_RESET);
    if (result != FF_OK) {
        return SDL_SetError("Unable to reset force feedback device: %s", FFStrError(result));
    }

    result = FFDeviceSendForceFeedbackCommand(device->ffdevice, FFSFFC_SETACTUATORSON);
    if (result != FF_OK) {
        return SDL_SetError("Unable to enable force feedback actuators: %s", FFStrError(result));
    }

    /* Create the effect */
    device->ffeffect = CreateRumbleEffectData(magnitude, duration_ms);
    if (!device->ffeffect) {
        return SDL_OutOfMemory();
    }

    result = FFDeviceCreateEffect(device->ffdevice, kFFEffectType_Sine_ID,
                               device->ffeffect, &device->ffeffect_ref);
    if (result != FF_OK) {
        return SDL_SetError("Haptic: Unable to create effect: %s", FFStrError(result));
    }
    return 0;
}

static int
DARWIN_JoystickRumble(SDL_Joystick * joystick, Uint16 low_frequency_rumble, Uint16 high_frequency_rumble, Uint32 duration_ms)
{
    HRESULT result;
    recDevice *device = joystick->hwdata;

    /* Scale and average the two rumble strengths */
    Sint16 magnitude = (Sint16)(((low_frequency_rumble / 2) + (high_frequency_rumble / 2)) / 2);

    if (!device->ffservice) {
        return SDL_Unsupported();
    }

    if (device->ff_initialized) {
        FFPERIODIC *periodic = ((FFPERIODIC *)device->ffeffect->lpvTypeSpecificParams);
        device->ffeffect->dwDuration = duration_ms * 1000; /* In microseconds. */
        periodic->dwMagnitude = CONVERT_MAGNITUDE(magnitude);

        result = FFEffectSetParameters(device->ffeffect_ref, device->ffeffect,
                                    (FFEP_DURATION | FFEP_TYPESPECIFICPARAMS));
        if (result != FF_OK) {
            return SDL_SetError("Unable to update rumble effect: %s", FFStrError(result));
        }
    } else {
        if (DARWIN_JoystickInitRumble(device, magnitude, duration_ms) < 0) {
            return -1;
        }
        device->ff_initialized = SDL_TRUE;
    }

    result = FFEffectStart(device->ffeffect_ref, 1, 0);
    if (result != FF_OK) {
        return SDL_SetError("Unable to run the rumble effect: %s", FFStrError(result));
    }
    return 0;
}

static void
DARWIN_JoystickUpdate(SDL_Joystick * joystick)
{
    recDevice *device = joystick->hwdata;
    recElement *element;
    SInt32 value, range;
    int i;

    if (!device) {
        return;
    }

    if (device->removed) {      /* device was unplugged; ignore it. */
        if (joystick->hwdata) {
            joystick->force_recentering = SDL_TRUE;
            joystick->hwdata = NULL;
        }
        return;
    }

    element = device->firstAxis;
    i = 0;

    int goodRead = SDL_FALSE;
    while (element) {
        goodRead = GetHIDScaledCalibratedState(device, element, -32768, 32767, &value);
        if (goodRead) {
            SDL_PrivateJoystickAxis(joystick, i, value);
        }

        element = element->pNext;
        ++i;
    }

    element = device->firstButton;
    i = 0;
    while (element) {
        goodRead = GetHIDElementState(device, element, &value);
        if (goodRead) {
            if (value > 1) {          /* handle pressure-sensitive buttons */
                value = 1;
            }
            SDL_PrivateJoystickButton(joystick, i, value);
        }

        element = element->pNext;
        ++i;
    }

    element = device->firstHat;
    i = 0;
    
    while (element) {
        Uint8 pos = 0;

        range = (element->max - element->min + 1);
        goodRead = GetHIDElementState(device, element, &value);
        if (goodRead) {
            value -= element->min;
            if (range == 4) {         /* 4 position hatswitch - scale up value */
                value *= 2;
            } else if (range != 8) {    /* Neither a 4 nor 8 positions - fall back to default position (centered) */
                value = -1;
            }
            switch (value) {
            case 0:
                pos = SDL_HAT_UP;
                break;
            case 1:
                pos = SDL_HAT_RIGHTUP;
                break;
            case 2:
                pos = SDL_HAT_RIGHT;
                break;
            case 3:
                pos = SDL_HAT_RIGHTDOWN;
                break;
            case 4:
                pos = SDL_HAT_DOWN;
                break;
            case 5:
                pos = SDL_HAT_LEFTDOWN;
                break;
            case 6:
                pos = SDL_HAT_LEFT;
                break;
            case 7:
                pos = SDL_HAT_LEFTUP;
                break;
            default:
                /* Every other value is mapped to center. We do that because some
                 * joysticks use 8 and some 15 for this value, and apparently
                 * there are even more variants out there - so we try to be generous.
                 */
                pos = SDL_HAT_CENTERED;
                break;
            }

            SDL_PrivateJoystickHat(joystick, i, pos);
        }
        
        element = element->pNext;
        ++i;
    }
}

static void
DARWIN_JoystickClose(SDL_Joystick * joystick)
{
}

static void
DARWIN_JoystickQuit(void)
{
    while (FreeDevice(gpDeviceList)) {
        /* spin */
    }

    if (hidman) {
        IOHIDManagerUnscheduleFromRunLoop(hidman, CFRunLoopGetCurrent(), SDL_JOYSTICK_RUNLOOP_MODE);
        IOHIDManagerClose(hidman, kIOHIDOptionsTypeNone);
        CFRelease(hidman);
        hidman = NULL;
    }
}

SDL_JoystickDriver SDL_DARWIN_JoystickDriver =
{
    DARWIN_JoystickInit,
    DARWIN_JoystickGetCount,
    DARWIN_JoystickDetect,
    DARWIN_JoystickGetDeviceName,
    DARWIN_JoystickGetDevicePlayerIndex,
    DARWIN_JoystickGetDeviceGUID,
    DARWIN_JoystickGetDeviceInstanceID,
    DARWIN_JoystickOpen,
    DARWIN_JoystickRumble,
    DARWIN_JoystickUpdate,
    DARWIN_JoystickClose,
    DARWIN_JoystickQuit,
};

#endif /* SDL_JOYSTICK_IOKIT */

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