device/gamepad/gamepad_device_mac.mm - chromium/src - Git at Google

 // Copyright (c) 2018 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 #include "device/gamepad/gamepad_device_mac.h"

 #include "base/mac/foundation_util.h"
 #include "base/mac/scoped_cftyperef.h"

 #import <Foundation/Foundation.h>

 namespace {

 // http://www.usb.org/developers/hidpage
 const uint32_t kGenericDesktopUsagePage = 0x01;
 const uint32_t kGameControlsUsagePage = 0x05;
 const uint32_t kButtonUsagePage = 0x09;
 const uint32_t kJoystickUsageNumber = 0x04;
 const uint32_t kGameUsageNumber = 0x05;
 const uint32_t kMultiAxisUsageNumber = 0x08;
 const uint32_t kAxisMinimumUsageNumber = 0x30;

 const int kRumbleMagnitudeMax = 10000;

 float NormalizeAxis(CFIndex value, CFIndex min, CFIndex max) {
   return (2.f * (value - min) / static_cast<float>(max - min)) - 1.f;
 }

 float NormalizeUInt8Axis(uint8_t value, uint8_t min, uint8_t max) {
   return (2.f * (value - min) / static_cast<float>(max - min)) - 1.f;
 }

 float NormalizeUInt16Axis(uint16_t value, uint16_t min, uint16_t max) {
   return (2.f * (value - min) / static_cast<float>(max - min)) - 1.f;
 }

 float NormalizeUInt32Axis(uint32_t value, uint32_t min, uint32_t max) {
   return (2.f * (value - min) / static_cast<float>(max - min)) - 1.f;
 }

 }  // namespace

 namespace device {

 GamepadDeviceMac::GamepadDeviceMac(int location_id, IOHIDDeviceRef device_ref)
     : location_id_(location_id),
       device_ref_(device_ref),
       ff_device_ref_(nullptr),
       ff_effect_ref_(nullptr) {
   std::fill(button_elements_, button_elements_ + Gamepad::kButtonsLengthCap,
             nullptr);
   std::fill(axis_elements_, axis_elements_ + Gamepad::kAxesLengthCap, nullptr);
   std::fill(axis_minimums_, axis_minimums_ + Gamepad::kAxesLengthCap, 0);
   std::fill(axis_maximums_, axis_maximums_ + Gamepad::kAxesLengthCap, 0);
   std::fill(axis_report_sizes_, axis_report_sizes_ + Gamepad::kAxesLengthCap,
             0);

   if (device_ref != nullptr) {
     ff_device_ref_ = CreateForceFeedbackDevice(device_ref);
     if (ff_device_ref_ != nullptr) {
       ff_effect_ref_ = CreateForceFeedbackEffect(ff_device_ref_, &ff_effect_,
                                                  &ff_custom_force_, force_data_,
                                                  axes_data_, direction_data_);
     }
   }
 }

 GamepadDeviceMac::~GamepadDeviceMac() = default;

 void GamepadDeviceMac::DoShutdown() {
   SetZeroVibration();
   if (ff_device_ref_ != nullptr) {
     if (ff_effect_ref_ != nullptr)
       FFDeviceReleaseEffect(ff_device_ref_, ff_effect_ref_);
     FFReleaseDevice(ff_device_ref_);
   }
 }

 // static
 bool GamepadDeviceMac::CheckCollection(IOHIDElementRef element) {
   // Check that a parent collection of this element matches one of the usage
   // numbers that we are looking for.
   while ((element = IOHIDElementGetParent(element)) != NULL) {
     uint32_t usage_page = IOHIDElementGetUsagePage(element);
     uint32_t usage = IOHIDElementGetUsage(element);
     if (usage_page == kGenericDesktopUsagePage) {
       if (usage == kJoystickUsageNumber || usage == kGameUsageNumber ||
           usage == kMultiAxisUsageNumber) {
         return true;
       }
     }
   }
   return false;
 }

 bool GamepadDeviceMac::AddButtonsAndAxes(Gamepad* gamepad) {
   base::ScopedCFTypeRef<CFArrayRef> elements_cf(IOHIDDeviceCopyMatchingElements(
       device_ref_, nullptr, kIOHIDOptionsTypeNone));
   NSArray* elements = base::mac::CFToNSCast(elements_cf);
   DCHECK(elements);
   DCHECK(gamepad);
   gamepad->axes_length = 0;
   gamepad->buttons_length = 0;
   gamepad->timestamp = 0;
   memset(gamepad->axes, 0, sizeof(gamepad->axes));
   memset(gamepad->buttons, 0, sizeof(gamepad->buttons));

   bool mapped_all_axes = true;

   for (id elem in elements) {
     IOHIDElementRef element = reinterpret_cast<IOHIDElementRef>(elem);
     if (!CheckCollection(element))
       continue;

     uint32_t usage_page = IOHIDElementGetUsagePage(element);
     uint32_t usage = IOHIDElementGetUsage(element);
     if (IOHIDElementGetType(element) == kIOHIDElementTypeInput_Button &&
         usage_page == kButtonUsagePage) {
       uint32_t button_index = usage - 1;
       if (button_index < Gamepad::kButtonsLengthCap) {
         button_elements_[button_index] = element;
         gamepad->buttons_length =
             std::max(gamepad->buttons_length, button_index + 1);
       }
     } else if (IOHIDElementGetType(element) == kIOHIDElementTypeInput_Misc) {
       uint32_t axis_index = usage - kAxisMinimumUsageNumber;
       if (axis_index < Gamepad::kAxesLengthCap) {
         axis_elements_[axis_index] = element;
         gamepad->axes_length = std::max(gamepad->axes_length, axis_index + 1);
       } else {
         mapped_all_axes = false;
       }
     }
   }

   if (!mapped_all_axes) {
     // For axes whose usage puts them outside the standard axesLengthCap range.
     uint32_t next_index = 0;
     for (id elem in elements) {
       IOHIDElementRef element = reinterpret_cast<IOHIDElementRef>(elem);
       if (!CheckCollection(element))
         continue;

       uint32_t usage_page = IOHIDElementGetUsagePage(element);
       uint32_t usage = IOHIDElementGetUsage(element);
       if (IOHIDElementGetType(element) == kIOHIDElementTypeInput_Misc &&
           usage - kAxisMinimumUsageNumber >= Gamepad::kAxesLengthCap &&
           usage_page <= kGameControlsUsagePage) {
         for (; next_index < Gamepad::kAxesLengthCap; ++next_index) {
           if (axis_elements_[next_index] == NULL)
             break;
         }
         if (next_index < Gamepad::kAxesLengthCap) {
           axis_elements_[next_index] = element;
           gamepad->axes_length = std::max(gamepad->axes_length, next_index + 1);
         }
       }

       if (next_index >= Gamepad::kAxesLengthCap)
         break;
     }
   }

   for (uint32_t axis_index = 0; axis_index < gamepad->axes_length;
        ++axis_index) {
     IOHIDElementRef element = axis_elements_[axis_index];
     if (element != NULL) {
       CFIndex axis_min = IOHIDElementGetLogicalMin(element);
       CFIndex axis_max = IOHIDElementGetLogicalMax(element);

       // Some HID axes report a logical range of -1 to 0 signed, which must be
       // interpreted as 0 to -1 unsigned for correct normalization behavior.
       if (axis_min == -1 && axis_max == 0) {
         axis_max = -1;
         axis_min = 0;
       }

       axis_minimums_[axis_index] = axis_min;
       axis_maximums_[axis_index] = axis_max;
       axis_report_sizes_[axis_index] = IOHIDElementGetReportSize(element);
     }
   }
   return (gamepad->axes_length > 0 || gamepad->buttons_length > 0);
 }

 void GamepadDeviceMac::UpdateGamepadForValue(IOHIDValueRef value,
                                              Gamepad* gamepad) {
   DCHECK(gamepad);
   IOHIDElementRef element = IOHIDValueGetElement(value);
   uint32_t value_length = IOHIDValueGetLength(value);
   if (value_length > 4) {
     // Workaround for bizarre issue with PS3 controllers that try to return
     // massive (30+ byte) values and crash IOHIDValueGetIntegerValue
     return;
   }

   // Find and fill in the associated button event, if any.
   for (size_t i = 0; i < gamepad->buttons_length; ++i) {
     if (button_elements_[i] == element) {
       bool pressed = IOHIDValueGetIntegerValue(value);
       gamepad->buttons[i].pressed = pressed;
       gamepad->buttons[i].value = pressed ? 1.f : 0.f;
       gamepad->timestamp =
           std::max(gamepad->timestamp, IOHIDValueGetTimeStamp(value));
       return;
     }
   }

   // Find and fill in the associated axis event, if any.
   for (size_t i = 0; i < gamepad->axes_length; ++i) {
     if (axis_elements_[i] == element) {
       CFIndex axis_min = axis_minimums_[i];
       CFIndex axis_max = axis_maximums_[i];
       CFIndex axis_value = IOHIDValueGetIntegerValue(value);

       if (axis_min > axis_max) {
         // We'll need to interpret this axis as unsigned during normalization.
         switch (axis_report_sizes_[i]) {
           case 8:
             gamepad->axes[i] =
                 NormalizeUInt8Axis(axis_value, axis_min, axis_max);
             break;
           case 16:
             gamepad->axes[i] =
                 NormalizeUInt16Axis(axis_value, axis_min, axis_max);
             break;
           case 32:
             gamepad->axes[i] =
                 NormalizeUInt32Axis(axis_value, axis_min, axis_max);
             break;
         }
       } else {
         gamepad->axes[i] = NormalizeAxis(axis_value, axis_min, axis_max);
       }

       gamepad->timestamp =
           std::max(gamepad->timestamp, IOHIDValueGetTimeStamp(value));
       return;
     }
   }
 }

 void GamepadDeviceMac::SetVibration(double strong_magnitude,
                                     double weak_magnitude) {
   FFCUSTOMFORCE* ff_custom_force =
       static_cast<FFCUSTOMFORCE*>(ff_effect_.lpvTypeSpecificParams);
   DCHECK(ff_custom_force);
   DCHECK(ff_custom_force->rglForceData);

   ff_custom_force->rglForceData[0] =
       static_cast<LONG>(strong_magnitude * kRumbleMagnitudeMax);
   ff_custom_force->rglForceData[1] =
       static_cast<LONG>(weak_magnitude * kRumbleMagnitudeMax);

   // Download the effect to the device and start the effect.
   HRESULT res = FFEffectSetParameters(
       ff_effect_ref_, &ff_effect_,
       FFEP_DURATION | FFEP_STARTDELAY | FFEP_TYPESPECIFICPARAMS);
   if (res == FF_OK)
     FFEffectStart(ff_effect_ref_, 1, FFES_SOLO);
 }

 void GamepadDeviceMac::SetZeroVibration() {
   FFEffectStop(ff_effect_ref_);
 }

 // static
 FFDeviceObjectReference GamepadDeviceMac::CreateForceFeedbackDevice(
     IOHIDDeviceRef device_ref) {
   io_service_t service = IOHIDDeviceGetService(device_ref);

   if (service == MACH_PORT_NULL)
     return nullptr;

   HRESULT res = FFIsForceFeedback(service);
   if (res != FF_OK)
     return nullptr;

   FFDeviceObjectReference ff_device_ref;
   res = FFCreateDevice(service, &ff_device_ref);
   if (res != FF_OK)
     return nullptr;

   return ff_device_ref;
 }

 // static
 FFEffectObjectReference GamepadDeviceMac::CreateForceFeedbackEffect(
     FFDeviceObjectReference ff_device_ref,
     FFEFFECT* ff_effect,
     FFCUSTOMFORCE* ff_custom_force,
     LONG* force_data,
     DWORD* axes_data,
     LONG* direction_data) {
   DCHECK(ff_effect);
   DCHECK(ff_custom_force);
   DCHECK(force_data);
   DCHECK(axes_data);
   DCHECK(direction_data);

   FFCAPABILITIES caps;
   HRESULT res = FFDeviceGetForceFeedbackCapabilities(ff_device_ref, &caps);
   if (res != FF_OK)
     return nullptr;

   if ((caps.supportedEffects & FFCAP_ET_CUSTOMFORCE) == 0)
     return nullptr;

   force_data[0] = 0;
   force_data[1] = 0;
   axes_data[0] = caps.ffAxes[0];
   axes_data[1] = caps.ffAxes[1];
   direction_data[0] = 0;
   direction_data[1] = 0;
   ff_custom_force->cChannels = 2;
   ff_custom_force->cSamples = 2;
   ff_custom_force->rglForceData = force_data;
   ff_custom_force->dwSamplePeriod = 100000;  // 100 ms
   ff_effect->dwSize = sizeof(FFEFFECT);
   ff_effect->dwFlags = FFEFF_OBJECTOFFSETS | FFEFF_SPHERICAL;
   ff_effect->dwDuration = 5000000;     // 5 seconds
   ff_effect->dwSamplePeriod = 100000;  // 100 ms
   ff_effect->dwGain = 10000;
   ff_effect->dwTriggerButton = FFEB_NOTRIGGER;
   ff_effect->dwTriggerRepeatInterval = 0;
   ff_effect->cAxes = caps.numFfAxes;
   ff_effect->rgdwAxes = axes_data;
   ff_effect->rglDirection = direction_data;
   ff_effect->lpEnvelope = nullptr;
   ff_effect->cbTypeSpecificParams = sizeof(FFCUSTOMFORCE);
   ff_effect->lpvTypeSpecificParams = ff_custom_force;
   ff_effect->dwStartDelay = 0;

   FFEffectObjectReference ff_effect_ref;
   res = FFDeviceCreateEffect(ff_device_ref, kFFEffectType_CustomForce_ID,
                              ff_effect, &ff_effect_ref);
   if (res != FF_OK)
     return nullptr;

   return ff_effect_ref;
 }

 }  // namespace device
	// Copyright (c) 2018 The Chromium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	#include "device/gamepad/gamepad_device_mac.h"

	#include "base/mac/foundation_util.h"
	#include "base/mac/scoped_cftyperef.h"

	#import <Foundation/Foundation.h>

	namespace {

	// http://www.usb.org/developers/hidpage
	const uint32_t kGenericDesktopUsagePage = 0x01;
	const uint32_t kGameControlsUsagePage = 0x05;
	const uint32_t kButtonUsagePage = 0x09;
	const uint32_t kJoystickUsageNumber = 0x04;
	const uint32_t kGameUsageNumber = 0x05;
	const uint32_t kMultiAxisUsageNumber = 0x08;
	const uint32_t kAxisMinimumUsageNumber = 0x30;

	const int kRumbleMagnitudeMax = 10000;

	float NormalizeAxis(CFIndex value, CFIndex min, CFIndex max) {
	return (2.f * (value - min) / static_cast<float>(max - min)) - 1.f;
	}

	float NormalizeUInt8Axis(uint8_t value, uint8_t min, uint8_t max) {
	return (2.f * (value - min) / static_cast<float>(max - min)) - 1.f;
	}

	float NormalizeUInt16Axis(uint16_t value, uint16_t min, uint16_t max) {
	return (2.f * (value - min) / static_cast<float>(max - min)) - 1.f;
	}

	float NormalizeUInt32Axis(uint32_t value, uint32_t min, uint32_t max) {
	return (2.f * (value - min) / static_cast<float>(max - min)) - 1.f;
	}

	} // namespace

	namespace device {

	GamepadDeviceMac::GamepadDeviceMac(int location_id, IOHIDDeviceRef device_ref)
	: location_id_(location_id),
	device_ref_(device_ref),
	ff_device_ref_(nullptr),
	ff_effect_ref_(nullptr) {
	std::fill(button_elements_, button_elements_ + Gamepad::kButtonsLengthCap,
	nullptr);
	std::fill(axis_elements_, axis_elements_ + Gamepad::kAxesLengthCap, nullptr);
	std::fill(axis_minimums_, axis_minimums_ + Gamepad::kAxesLengthCap, 0);
	std::fill(axis_maximums_, axis_maximums_ + Gamepad::kAxesLengthCap, 0);
	std::fill(axis_report_sizes_, axis_report_sizes_ + Gamepad::kAxesLengthCap,
	0);

	if (device_ref != nullptr) {
	ff_device_ref_ = CreateForceFeedbackDevice(device_ref);
	if (ff_device_ref_ != nullptr) {
	ff_effect_ref_ = CreateForceFeedbackEffect(ff_device_ref_, &ff_effect_,
	&ff_custom_force_, force_data_,
	axes_data_, direction_data_);
	}
	}
	}

	GamepadDeviceMac::~GamepadDeviceMac() = default;

	void GamepadDeviceMac::DoShutdown() {
	SetZeroVibration();
	if (ff_device_ref_ != nullptr) {
	if (ff_effect_ref_ != nullptr)
	FFDeviceReleaseEffect(ff_device_ref_, ff_effect_ref_);
	FFReleaseDevice(ff_device_ref_);
	}
	}

	// static
	bool GamepadDeviceMac::CheckCollection(IOHIDElementRef element) {
	// Check that a parent collection of this element matches one of the usage
	// numbers that we are looking for.
	while ((element = IOHIDElementGetParent(element)) != NULL) {
	uint32_t usage_page = IOHIDElementGetUsagePage(element);
	uint32_t usage = IOHIDElementGetUsage(element);
	if (usage_page == kGenericDesktopUsagePage) {
	if (usage == kJoystickUsageNumber \|\| usage == kGameUsageNumber \|\|
	usage == kMultiAxisUsageNumber) {
	return true;
	}
	}
	}
	return false;
	}

	bool GamepadDeviceMac::AddButtonsAndAxes(Gamepad* gamepad) {
	base::ScopedCFTypeRef<CFArrayRef> elements_cf(IOHIDDeviceCopyMatchingElements(
	device_ref_, nullptr, kIOHIDOptionsTypeNone));
	NSArray* elements = base::mac::CFToNSCast(elements_cf);
	DCHECK(elements);
	DCHECK(gamepad);
	gamepad->axes_length = 0;
	gamepad->buttons_length = 0;
	gamepad->timestamp = 0;
	memset(gamepad->axes, 0, sizeof(gamepad->axes));
	memset(gamepad->buttons, 0, sizeof(gamepad->buttons));

	bool mapped_all_axes = true;

	for (id elem in elements) {
	IOHIDElementRef element = reinterpret_cast<IOHIDElementRef>(elem);
	if (!CheckCollection(element))
	continue;

	uint32_t usage_page = IOHIDElementGetUsagePage(element);
	uint32_t usage = IOHIDElementGetUsage(element);
	if (IOHIDElementGetType(element) == kIOHIDElementTypeInput_Button &&
	usage_page == kButtonUsagePage) {
	uint32_t button_index = usage - 1;
	if (button_index < Gamepad::kButtonsLengthCap) {
	button_elements_[button_index] = element;
	gamepad->buttons_length =
	std::max(gamepad->buttons_length, button_index + 1);
	}
	} else if (IOHIDElementGetType(element) == kIOHIDElementTypeInput_Misc) {
	uint32_t axis_index = usage - kAxisMinimumUsageNumber;
	if (axis_index < Gamepad::kAxesLengthCap) {
	axis_elements_[axis_index] = element;
	gamepad->axes_length = std::max(gamepad->axes_length, axis_index + 1);
	} else {
	mapped_all_axes = false;
	}
	}
	}

	if (!mapped_all_axes) {
	// For axes whose usage puts them outside the standard axesLengthCap range.
	uint32_t next_index = 0;
	for (id elem in elements) {
	IOHIDElementRef element = reinterpret_cast<IOHIDElementRef>(elem);
	if (!CheckCollection(element))
	continue;

	uint32_t usage_page = IOHIDElementGetUsagePage(element);
	uint32_t usage = IOHIDElementGetUsage(element);
	if (IOHIDElementGetType(element) == kIOHIDElementTypeInput_Misc &&
	usage - kAxisMinimumUsageNumber >= Gamepad::kAxesLengthCap &&
	usage_page <= kGameControlsUsagePage) {
	for (; next_index < Gamepad::kAxesLengthCap; ++next_index) {
	if (axis_elements_[next_index] == NULL)
	break;
	}
	if (next_index < Gamepad::kAxesLengthCap) {
	axis_elements_[next_index] = element;
	gamepad->axes_length = std::max(gamepad->axes_length, next_index + 1);
	}
	}

	if (next_index >= Gamepad::kAxesLengthCap)
	break;
	}
	}

	for (uint32_t axis_index = 0; axis_index < gamepad->axes_length;
	++axis_index) {
	IOHIDElementRef element = axis_elements_[axis_index];
	if (element != NULL) {
	CFIndex axis_min = IOHIDElementGetLogicalMin(element);
	CFIndex axis_max = IOHIDElementGetLogicalMax(element);

	// Some HID axes report a logical range of -1 to 0 signed, which must be
	// interpreted as 0 to -1 unsigned for correct normalization behavior.
	if (axis_min == -1 && axis_max == 0) {
	axis_max = -1;
	axis_min = 0;
	}

	axis_minimums_[axis_index] = axis_min;
	axis_maximums_[axis_index] = axis_max;
	axis_report_sizes_[axis_index] = IOHIDElementGetReportSize(element);
	}
	}
	return (gamepad->axes_length > 0 \|\| gamepad->buttons_length > 0);
	}

	void GamepadDeviceMac::UpdateGamepadForValue(IOHIDValueRef value,
	Gamepad* gamepad) {
	DCHECK(gamepad);
	IOHIDElementRef element = IOHIDValueGetElement(value);
	uint32_t value_length = IOHIDValueGetLength(value);
	if (value_length > 4) {
	// Workaround for bizarre issue with PS3 controllers that try to return
	// massive (30+ byte) values and crash IOHIDValueGetIntegerValue
	return;
	}

	// Find and fill in the associated button event, if any.
	for (size_t i = 0; i < gamepad->buttons_length; ++i) {
	if (button_elements_[i] == element) {
	bool pressed = IOHIDValueGetIntegerValue(value);
	gamepad->buttons[i].pressed = pressed;
	gamepad->buttons[i].value = pressed ? 1.f : 0.f;
	gamepad->timestamp =
	std::max(gamepad->timestamp, IOHIDValueGetTimeStamp(value));
	return;
	}
	}

	// Find and fill in the associated axis event, if any.
	for (size_t i = 0; i < gamepad->axes_length; ++i) {
	if (axis_elements_[i] == element) {
	CFIndex axis_min = axis_minimums_[i];
	CFIndex axis_max = axis_maximums_[i];
	CFIndex axis_value = IOHIDValueGetIntegerValue(value);

	if (axis_min > axis_max) {
	// We'll need to interpret this axis as unsigned during normalization.
	switch (axis_report_sizes_[i]) {
	case 8:
	gamepad->axes[i] =
	NormalizeUInt8Axis(axis_value, axis_min, axis_max);
	break;
	case 16:
	gamepad->axes[i] =
	NormalizeUInt16Axis(axis_value, axis_min, axis_max);
	break;
	case 32:
	gamepad->axes[i] =
	NormalizeUInt32Axis(axis_value, axis_min, axis_max);
	break;
	}
	} else {
	gamepad->axes[i] = NormalizeAxis(axis_value, axis_min, axis_max);
	}

	gamepad->timestamp =
	std::max(gamepad->timestamp, IOHIDValueGetTimeStamp(value));
	return;
	}
	}
	}

	void GamepadDeviceMac::SetVibration(double strong_magnitude,
	double weak_magnitude) {
	FFCUSTOMFORCE* ff_custom_force =
	static_cast<FFCUSTOMFORCE*>(ff_effect_.lpvTypeSpecificParams);
	DCHECK(ff_custom_force);
	DCHECK(ff_custom_force->rglForceData);

	ff_custom_force->rglForceData[0] =
	static_cast<LONG>(strong_magnitude * kRumbleMagnitudeMax);
	ff_custom_force->rglForceData[1] =
	static_cast<LONG>(weak_magnitude * kRumbleMagnitudeMax);

	// Download the effect to the device and start the effect.
	HRESULT res = FFEffectSetParameters(
	ff_effect_ref_, &ff_effect_,
	FFEP_DURATION \| FFEP_STARTDELAY \| FFEP_TYPESPECIFICPARAMS);
	if (res == FF_OK)
	FFEffectStart(ff_effect_ref_, 1, FFES_SOLO);
	}

	void GamepadDeviceMac::SetZeroVibration() {
	FFEffectStop(ff_effect_ref_);
	}

	// static
	FFDeviceObjectReference GamepadDeviceMac::CreateForceFeedbackDevice(
	IOHIDDeviceRef device_ref) {
	io_service_t service = IOHIDDeviceGetService(device_ref);

	if (service == MACH_PORT_NULL)
	return nullptr;

	HRESULT res = FFIsForceFeedback(service);
	if (res != FF_OK)
	return nullptr;

	FFDeviceObjectReference ff_device_ref;
	res = FFCreateDevice(service, &ff_device_ref);
	if (res != FF_OK)
	return nullptr;

	return ff_device_ref;
	}

	// static
	FFEffectObjectReference GamepadDeviceMac::CreateForceFeedbackEffect(
	FFDeviceObjectReference ff_device_ref,
	FFEFFECT* ff_effect,
	FFCUSTOMFORCE* ff_custom_force,
	LONG* force_data,
	DWORD* axes_data,
	LONG* direction_data) {
	DCHECK(ff_effect);
	DCHECK(ff_custom_force);
	DCHECK(force_data);
	DCHECK(axes_data);
	DCHECK(direction_data);

	FFCAPABILITIES caps;
	HRESULT res = FFDeviceGetForceFeedbackCapabilities(ff_device_ref, &caps);
	if (res != FF_OK)
	return nullptr;

	if ((caps.supportedEffects & FFCAP_ET_CUSTOMFORCE) == 0)
	return nullptr;

	force_data[0] = 0;
	force_data[1] = 0;
	axes_data[0] = caps.ffAxes[0];
	axes_data[1] = caps.ffAxes[1];
	direction_data[0] = 0;
	direction_data[1] = 0;
	ff_custom_force->cChannels = 2;
	ff_custom_force->cSamples = 2;
	ff_custom_force->rglForceData = force_data;
	ff_custom_force->dwSamplePeriod = 100000; // 100 ms
	ff_effect->dwSize = sizeof(FFEFFECT);
	ff_effect->dwFlags = FFEFF_OBJECTOFFSETS \| FFEFF_SPHERICAL;
	ff_effect->dwDuration = 5000000; // 5 seconds
	ff_effect->dwSamplePeriod = 100000; // 100 ms
	ff_effect->dwGain = 10000;
	ff_effect->dwTriggerButton = FFEB_NOTRIGGER;
	ff_effect->dwTriggerRepeatInterval = 0;
	ff_effect->cAxes = caps.numFfAxes;
	ff_effect->rgdwAxes = axes_data;
	ff_effect->rglDirection = direction_data;
	ff_effect->lpEnvelope = nullptr;
	ff_effect->cbTypeSpecificParams = sizeof(FFCUSTOMFORCE);
	ff_effect->lpvTypeSpecificParams = ff_custom_force;
	ff_effect->dwStartDelay = 0;

	FFEffectObjectReference ff_effect_ref;
	res = FFDeviceCreateEffect(ff_device_ref, kFFEffectType_CustomForce_ID,
	ff_effect, &ff_effect_ref);
	if (res != FF_OK)
	return nullptr;

	return ff_effect_ref;
	}

	} // namespace device