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libretro: read the Nunchuk's accelerometer #484

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fff7566
libretro: add a sensor sub-device index to libretro.h
XenuIsWatching Aug 21, 2026
fe012fc
libretro: read the Nunchuk's accelerometer
XenuIsWatching Aug 21, 2026
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36 changes: 36 additions & 0 deletions Externals/libretro-common/include/libretro.h
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Original file line number Diff line number Diff line change
Expand Up @@ -4868,6 +4868,42 @@ enum retro_sensor_action
#define RETRO_SENSOR_ILLUMINANCE 6
/** @} */

/** @defgroup RETRO_SENSOR_SUBDEVICE Sensor Sub-Device Index
* @{
*/

/**
* The number of bits that a sub-device index is shifted by within a sensor ID
* or a \c retro_sensor_action.
*
* Addresses more than one sensor of the same kind on a single port.
* Index 0 denotes the controller itself and encodes to the values already in
* use (<tt>RETRO_SENSOR_SUBDEVICE(0, id) == id</tt>). Index 1 and above denote
* sub-devices, in whatever order the device type implies.
*
* @note \c retro_sensor_action is an enum, so an encoded action must be cast at
* the call site. \c RETRO_SENSOR_DUMMY pins the underlying type to \c int, so
* the encoded value is in range.
*
* @see RETRO_SENSOR_ID
* @see retro_sensor_action
*/
#define RETRO_SENSOR_INDEX_SHIFT 8

/** Mask of the bits below the sub-device index. */
#define RETRO_SENSOR_INDEX_MASK ((1u << RETRO_SENSOR_INDEX_SHIFT) - 1u)

/** Returns the sub-device index encoded in \c id; 0 is the controller itself. */
#define RETRO_SENSOR_INDEX(id) ((unsigned)(id) >> RETRO_SENSOR_INDEX_SHIFT)

/** Returns the sensor ID or action in \c id, without its sub-device index. */
#define RETRO_SENSOR_BASE(id) ((unsigned)(id) & RETRO_SENSOR_INDEX_MASK)

/** Addresses sensor \c id on sub-device \c index of a port. */
#define RETRO_SENSOR_SUBDEVICE(index, id) \
((unsigned)((((unsigned)(index)) << RETRO_SENSOR_INDEX_SHIFT) | ((unsigned)(id))))
/** @} */

/**
* Adjusts the state of a sensor.
*
Expand Down
247 changes: 152 additions & 95 deletions Source/Core/DolphinLibretro/Input.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -92,6 +92,11 @@ typedef enum {
SENSOR_COUNT
} sensor_type_t;

/* Which sub-device of a Wii Remote's port the Nunchuk's accelerometer is. The
* remote itself is 0. A real Nunchuk has no gyroscope, so it is asked for an
* accelerometer and nothing else. */
#define NUNCHUK_SENSOR_SUBDEVICE 1

void retro_set_controller_port_device_gc(unsigned port, unsigned device);
void retro_set_controller_port_device_wii(unsigned port, unsigned device);

Expand All @@ -106,12 +111,12 @@ static struct retro_rumble_interface rumble{};
static unsigned input_types[8];
static bool g_init_wiimotes = false;
static bool s_sensor_init_pending = false;
static bool sensor_enabled[NUM_CONTROLLERS_FOR_SENSORS][SENSOR_COUNT] = {};
static bool sensor_enabled[NUM_CONTROLLERS_FOR_SENSORS][NUM_SENSOR_SUBDEVICES][SENSOR_COUNT] = {};
static int port_max;
double g_accel_pos[NUM_CONTROLLERS_FOR_SENSORS][3] = {}; // x, y, z
double g_accel_neg[NUM_CONTROLLERS_FOR_SENSORS][3] = {}; // x, y, z
double g_gyro_pos[NUM_CONTROLLERS_FOR_SENSORS][3] = {}; // x, y, z
double g_gyro_neg[NUM_CONTROLLERS_FOR_SENSORS][3] = {}; // x, y, z
double g_accel_pos[NUM_CONTROLLERS_FOR_SENSORS][NUM_SENSOR_SUBDEVICES][3] = {}; // x, y, z
double g_accel_neg[NUM_CONTROLLERS_FOR_SENSORS][NUM_SENSOR_SUBDEVICES][3] = {}; // x, y, z
double g_gyro_pos[NUM_CONTROLLERS_FOR_SENSORS][NUM_SENSOR_SUBDEVICES][3] = {}; // x, y, z
double g_gyro_neg[NUM_CONTROLLERS_FOR_SENSORS][NUM_SENSOR_SUBDEVICES][3] = {}; // x, y, z

static struct retro_input_descriptor descGC[] = {
{0, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_LEFT, "Left"},
Expand Down Expand Up @@ -660,18 +665,33 @@ void InitSensors()
{
if (sensor_interface.set_sensor_state)
{
sensor_enabled[i][SENSOR_ACCELEROMETER] = sensor_interface.set_sensor_state(i, RETRO_SENSOR_ACCELEROMETER_ENABLE, 60);
sensor_enabled[i][SENSOR_GYRO] = sensor_interface.set_sensor_state(i, RETRO_SENSOR_GYROSCOPE_ENABLE, 60);

if (sensor_enabled[i][SENSOR_ACCELEROMETER] || sensor_enabled[i][SENSOR_GYRO])
for (unsigned s = 0; s < NUM_SENSOR_SUBDEVICES; s++)
{
auto sensor = std::make_shared<SensorDevice>(i);
sensor->RegisterAll();
g_controller_interface.AddDevice(sensor);
}
// The sub-device rides in the high bits of the action. A frontend
// that does not know about sub-devices returns false for anything but
// 0; the flag stays clear and nothing binds.
const retro_sensor_action accel_on = static_cast<retro_sensor_action>(
RETRO_SENSOR_SUBDEVICE(s, RETRO_SENSOR_ACCELEROMETER_ENABLE));
sensor_enabled[i][s][SENSOR_ACCELEROMETER] =
sensor_interface.set_sensor_state(i, accel_on, 60);

// Only the remote itself has a gyroscope to ask for; a Nunchuk has none.
if (s == 0)
{
sensor_enabled[i][s][SENSOR_GYRO] =
sensor_interface.set_sensor_state(i, RETRO_SENSOR_GYROSCOPE_ENABLE, 60);
}

INFO_LOG_FMT(BOOT, "Sensor interface: Port: {} ACCELEROMETER: {} GYROSCOPE: {}", i,
sensor_enabled[i][SENSOR_ACCELEROMETER], sensor_enabled[i][SENSOR_GYRO]);
if (sensor_enabled[i][s][SENSOR_ACCELEROMETER] || sensor_enabled[i][s][SENSOR_GYRO])
{
auto sensor = std::make_shared<SensorDevice>(i, s);
sensor->RegisterAll();
g_controller_interface.AddDevice(sensor);
}

INFO_LOG_FMT(BOOT, "Sensor interface: Port: {} Sub-device: {} ACCELEROMETER: {} GYROSCOPE: {}",
i, s, sensor_enabled[i][s][SENSOR_ACCELEROMETER], sensor_enabled[i][s][SENSOR_GYRO]);
}
}
}

Expand All @@ -698,15 +718,20 @@ void Shutdown()
{
Pad::ResetRumble(i);

// Was crossed over and hardcoded to port 0, leaving sensors running.
if (sensor_enabled[i][SENSOR_ACCELEROMETER])
sensor_interface.set_sensor_state(i, RETRO_SENSOR_ACCELEROMETER_DISABLE, 0);
// Disable each sensor on the port it was enabled for.
for (unsigned s = 0; s < NUM_SENSOR_SUBDEVICES; s++)
{
if (sensor_enabled[i][s][SENSOR_ACCELEROMETER])
sensor_interface.set_sensor_state(i, static_cast<retro_sensor_action>(
RETRO_SENSOR_SUBDEVICE(s, RETRO_SENSOR_ACCELEROMETER_DISABLE)), 0);

if (sensor_enabled[i][SENSOR_GYRO])
sensor_interface.set_sensor_state(i, RETRO_SENSOR_GYROSCOPE_DISABLE, 0);
if (sensor_enabled[i][s][SENSOR_GYRO])
sensor_interface.set_sensor_state(i, static_cast<retro_sensor_action>(
RETRO_SENSOR_SUBDEVICE(s, RETRO_SENSOR_GYROSCOPE_DISABLE)), 0);

sensor_enabled[i][SENSOR_ACCELEROMETER] = false;
sensor_enabled[i][SENSOR_GYRO] = false;
sensor_enabled[i][s][SENSOR_ACCELEROMETER] = false;
sensor_enabled[i][s][SENSOR_GYRO] = false;
}
}

Keyboard::Shutdown();
Expand All @@ -716,20 +741,24 @@ void Shutdown()
rumble.set_rumble_state = nullptr;
}

void UpdateAccelerometer(unsigned port)
void UpdateAccelerometer(unsigned port, unsigned subdevice)
{
if (!sensor_enabled[port][SENSOR_ACCELEROMETER] || !sensor_interface.get_sensor_input)
if (!sensor_enabled[port][subdevice][SENSOR_ACCELEROMETER] || !sensor_interface.get_sensor_input)
return;

static const float G = 9.80665f;

// read raw sensor values
float ax = sensor_interface.get_sensor_input(port, RETRO_SENSOR_ACCELEROMETER_X) * G;
float ay = sensor_interface.get_sensor_input(port, RETRO_SENSOR_ACCELEROMETER_Y) * G;
float az = sensor_interface.get_sensor_input(port, RETRO_SENSOR_ACCELEROMETER_Z) * G;

// Collapsed, so a sideways remote with the dongle fitted still rotates.
if (wiimote_base_device(input_types[port]) == RETRO_DEVICE_WIIMOTE_SW)
float ax = sensor_interface.get_sensor_input(
port, RETRO_SENSOR_SUBDEVICE(subdevice, RETRO_SENSOR_ACCELEROMETER_X)) * G;
float ay = sensor_interface.get_sensor_input(
port, RETRO_SENSOR_SUBDEVICE(subdevice, RETRO_SENSOR_ACCELEROMETER_Y)) * G;
float az = sensor_interface.get_sensor_input(
port, RETRO_SENSOR_SUBDEVICE(subdevice, RETRO_SENSOR_ACCELEROMETER_Z)) * G;

// Holding the remote sideways rotates what its sensors read. Sub-device 0
// only: a Nunchuk is held the same way round regardless.
if (subdevice == 0 && wiimote_base_device(input_types[port]) == RETRO_DEVICE_WIIMOTE_SW)
{
float rx = -ay; // rotate 90° clockwise
float ry = ax;
Expand All @@ -738,19 +767,20 @@ void UpdateAccelerometer(unsigned port)
}

// write rotated values
g_accel_pos[port][0] = std::max(0.0f, ax);
g_accel_neg[port][0] = std::max(0.0f, -ax);
g_accel_pos[port][subdevice][0] = std::max(0.0f, ax);
g_accel_neg[port][subdevice][0] = std::max(0.0f, -ax);

g_accel_pos[port][1] = std::max(0.0f, ay);
g_accel_neg[port][1] = std::max(0.0f, -ay);
g_accel_pos[port][subdevice][1] = std::max(0.0f, ay);
g_accel_neg[port][subdevice][1] = std::max(0.0f, -ay);

g_accel_pos[port][2] = std::max(0.0f, az);
g_accel_neg[port][2] = std::max(0.0f, -az);
g_accel_pos[port][subdevice][2] = std::max(0.0f, az);
g_accel_neg[port][subdevice][2] = std::max(0.0f, -az);
}

void UpdateGyro(unsigned port)
{
if (!sensor_enabled[port][SENSOR_GYRO] || !sensor_interface.get_sensor_input)
// Sub-device 0 only: the gyroscope is the remote's, by way of MotionPlus.
if (!sensor_enabled[port][0][SENSOR_GYRO] || !sensor_interface.get_sensor_input)
return;

// rad/s about the remote's own axes: +X left, +Y back, +Z up.
Expand All @@ -766,16 +796,16 @@ void UpdateGyro(unsigned port)
gy = ry;
}

// Split across a one-sided pair; the expression parser clamps negatives away
// (see SensorDevice::RegisterAll).
g_gyro_pos[port][0] = std::max(0.0f, gx);
g_gyro_neg[port][0] = std::max(0.0f, -gx);
// Split each axis across a one-sided pair: the expression parser cannot
// carry a negative value (see SensorDevice::RegisterAll).
g_gyro_pos[port][0][0] = std::max(0.0f, gx);
g_gyro_neg[port][0][0] = std::max(0.0f, -gx);

g_gyro_pos[port][1] = std::max(0.0f, gy);
g_gyro_neg[port][1] = std::max(0.0f, -gy);
g_gyro_pos[port][0][1] = std::max(0.0f, gy);
g_gyro_neg[port][0][1] = std::max(0.0f, -gy);

g_gyro_pos[port][2] = std::max(0.0f, gz);
g_gyro_neg[port][2] = std::max(0.0f, -gz);
g_gyro_pos[port][0][2] = std::max(0.0f, gz);
g_gyro_neg[port][0][2] = std::max(0.0f, -gz);
}

void ResetControllers(const WiimoteUpdateFlags& f)
Expand Down Expand Up @@ -848,7 +878,8 @@ void Update()

for (int i = 0; i < port_max; ++i)
{
UpdateAccelerometer(i);
for (unsigned s = 0; s < NUM_SENSOR_SUBDEVICES; ++s)
UpdateAccelerometer(i, s);
UpdateGyro(i);
}

Expand All @@ -869,12 +900,12 @@ void Update()
}
}

static std::string GetQualifiedNameSensor(unsigned port)
static std::string GetQualifiedNameSensor(unsigned port, unsigned subdevice)
{
return ciface::Core::DeviceQualifier(
std::string(Libretro::Input::source),
static_cast<int>(port),
std::string("Sensor")
Libretro::Input::SensorDeviceName(subdevice)
).ToString();
}

Expand Down Expand Up @@ -1538,10 +1569,8 @@ void retro_set_controller_port_device_wii(unsigned port, unsigned device)
ControllerEmu::ControlGroup* ncButtons = wm->GetNunchukGroup(NunchukGroup::Buttons);
ControllerEmu::ControlGroup* ncStick = wm->GetNunchukGroup(NunchukGroup::Stick);
ControllerEmu::ControlGroup* ncShake = wm->GetNunchukGroup(NunchukGroup::Shake);
#if 0
ControllerEmu::ControlGroup* ncTilt = wm->GetNunchukGroup(NunchukGroup::Tilt);
ControllerEmu::ControlGroup* ncSwing = wm->GetNunchukGroup(NunchukGroup::Swing);
#endif
// Nunchuk Tilt and Swing stay unbound: its motion arrives below as a
// real accelerometer, and both sticks are already spoken for.
ncButtons->SetControlExpression(0, "X"); // C
ncButtons->SetControlExpression(1, "Y"); // Z
ncStick->SetControlExpression(0, "`" + devAnalog + ":Y0-`"); // Up
Expand Down Expand Up @@ -1578,58 +1607,86 @@ void retro_set_controller_port_device_wii(unsigned port, unsigned device)
wmButtons->SetControlExpression(3, "A"); // 2
}

// Map accel data to tilt expressions
if (Libretro::Input::sensor_enabled[port][SENSOR_ACCELEROMETER] ||
Libretro::Input::sensor_enabled[port][SENSOR_GYRO])
{
std::string devSensor = Libretro::Input::GetQualifiedNameSensor(port);
wmButtons->SetControlExpression(4, "Select"); // -
wmButtons->SetControlExpression(5, "Start"); // +
}

// Motion, for every remote configuration rather than only the ones with
// nothing on the expansion port.
if (Libretro::Input::sensor_enabled[port][0][SENSOR_ACCELEROMETER] ||
Libretro::Input::sensor_enabled[port][0][SENSOR_GYRO])
{
std::string devSensor = Libretro::Input::GetQualifiedNameSensor(port, 0);

if (Libretro::Input::sensor_enabled[port][SENSOR_ACCELEROMETER])
if (Libretro::Input::sensor_enabled[port][0][SENSOR_ACCELEROMETER])
{
// Accelerometer (6 inputs: Up, Down, Left, Right, Forward, Backward)
// Indices must match WiimoteEmu::LoadDefaults ordering (0..5)
auto* wmAccel = static_cast<ControllerEmu::IMUAccelerometer*>(
wm->GetWiimoteGroup(WiimoteEmu::WiimoteGroup::IMUAccelerometer));
if (wmAccel)
{
// Accelerometer (6 inputs: Up, Down, Left, Right, Forward, Backward)
// Indices must match WiimoteEmu::LoadDefaults ordering (0..5)
auto* wmAccel = static_cast<ControllerEmu::IMUAccelerometer*>(
wm->GetWiimoteGroup(WiimoteEmu::WiimoteGroup::IMUAccelerometer));
if (wmAccel)
{
wmAccel->SetControlExpression(0, "`" + devSensor + ":AccelZ+`"); // Up
wmAccel->SetControlExpression(1, "`" + devSensor + ":AccelZ-`"); // Down
wmAccel->SetControlExpression(2, "`" + devSensor + ":AccelX+`"); // Left
wmAccel->SetControlExpression(3, "`" + devSensor + ":AccelX-`"); // Right
wmAccel->SetControlExpression(4, "`" + devSensor + ":AccelY-`"); // Forward
wmAccel->SetControlExpression(5, "`" + devSensor + ":AccelY+`"); // Backward
}
wmAccel->SetControlExpression(0, "`" + devSensor + ":AccelZ+`"); // Up
wmAccel->SetControlExpression(1, "`" + devSensor + ":AccelZ-`"); // Down
wmAccel->SetControlExpression(2, "`" + devSensor + ":AccelX+`"); // Left
wmAccel->SetControlExpression(3, "`" + devSensor + ":AccelX-`"); // Right
wmAccel->SetControlExpression(4, "`" + devSensor + ":AccelY-`"); // Forward
wmAccel->SetControlExpression(5, "`" + devSensor + ":AccelY+`"); // Backward
}
}

// A sibling, not a child: nested, gyro-without-accelerometer bound neither.
if (Libretro::Input::sensor_enabled[port][SENSOR_GYRO])
// A sibling of the accelerometer branch: gyro without accelerometer
// must still bind.
if (Libretro::Input::sensor_enabled[port][0][SENSOR_GYRO])
{
// Gyroscope (6 inputs: PitchUp/Down, RollLeft/Right, YawLeft/Right)
auto* wmGyro = static_cast<ControllerEmu::IMUGyroscope*>(
wm->GetWiimoteGroup(WiimoteEmu::WiimoteGroup::IMUGyroscope));
if (wmGyro)
{
// Gyroscope (6 inputs: PitchUp/Down, RollLeft/Right, YawLeft/Right)
auto* wmGyro = static_cast<ControllerEmu::IMUGyroscope*>(
wm->GetWiimoteGroup(WiimoteEmu::WiimoteGroup::IMUGyroscope));
if (wmGyro)
{
// Right-hand rule about +X left, +Y back, +Z up: +X is pitch down,
// +Y rolls the top left, +Z swings the nose left. GetRawState()
// reads these as [1]-[0], [2]-[3], [4]-[5].
wmGyro->SetControlExpression(0, "`" + devSensor + ":GyroX-`"); // Pitch Up
wmGyro->SetControlExpression(1, "`" + devSensor + ":GyroX+`"); // Pitch Down
wmGyro->SetControlExpression(2, "`" + devSensor + ":GyroY+`"); // Roll Left
wmGyro->SetControlExpression(3, "`" + devSensor + ":GyroY-`"); // Roll Right
wmGyro->SetControlExpression(4, "`" + devSensor + ":GyroZ+`"); // Yaw Left
wmGyro->SetControlExpression(5, "`" + devSensor + ":GyroZ-`"); // Yaw Right
}
// Right-hand rule about the accelerometer's frame (+X left, +Y
// back, +Z up): +X is pitch down, +Y rolls the top left, +Z swings
// the nose left. GetRawState() reads [1]-[0], [2]-[3], [4]-[5].
wmGyro->SetControlExpression(0, "`" + devSensor + ":GyroX-`"); // Pitch Up
wmGyro->SetControlExpression(1, "`" + devSensor + ":GyroX+`"); // Pitch Down
wmGyro->SetControlExpression(2, "`" + devSensor + ":GyroY+`"); // Roll Left
wmGyro->SetControlExpression(3, "`" + devSensor + ":GyroY-`"); // Roll Right
wmGyro->SetControlExpression(4, "`" + devSensor + ":GyroZ+`"); // Yaw Left
wmGyro->SetControlExpression(5, "`" + devSensor + ":GyroZ-`"); // Yaw Right
}
}
else
}
else
{
// No sensors, so tilt falls back to a stick -- the right one when a
// Nunchuk is fitted, since the left one is the Nunchuk's.
const std::string tiltAxis = (device == RETRO_DEVICE_WIIMOTE_NC) ? "1" : "0";
wmTilt->SetControlExpression(0, "`" + devAnalog + ":Y" + tiltAxis + "-`"); // Forward
wmTilt->SetControlExpression(1, "`" + devAnalog + ":Y" + tiltAxis + "+`"); // Backward
wmTilt->SetControlExpression(2, "`" + devAnalog + ":X" + tiltAxis + "-`"); // Left
wmTilt->SetControlExpression(3, "`" + devAnalog + ":X" + tiltAxis + "+`"); // Right
}

// The Nunchuk's own accelerometer. Additive:
// Nunchuk::BuildDesiredExtensionState composes this group with swing, tilt
// and shake, and substitutes a flat device when nothing is bound.
if (device == RETRO_DEVICE_WIIMOTE_NC &&
Libretro::Input::sensor_enabled[port][NUNCHUK_SENSOR_SUBDEVICE][SENSOR_ACCELEROMETER])
{
auto* ncAccel = static_cast<ControllerEmu::IMUAccelerometer*>(
wm->GetNunchukGroup(NunchukGroup::IMUAccelerometer));
if (ncAccel)
{
wmTilt->SetControlExpression(0, "`" + devAnalog + ":Y0-`"); // Forward
wmTilt->SetControlExpression(1, "`" + devAnalog + ":Y0+`"); // Backward
wmTilt->SetControlExpression(2, "`" + devAnalog + ":X0-`"); // Left
wmTilt->SetControlExpression(3, "`" + devAnalog + ":X0+`"); // Right
// Same six-index order and frame as the remote's above.
const std::string devNunchuk =
Libretro::Input::GetQualifiedNameSensor(port, NUNCHUK_SENSOR_SUBDEVICE);
ncAccel->SetControlExpression(0, "`" + devNunchuk + ":AccelZ+`"); // Up
ncAccel->SetControlExpression(1, "`" + devNunchuk + ":AccelZ-`"); // Down
ncAccel->SetControlExpression(2, "`" + devNunchuk + ":AccelX+`"); // Left
ncAccel->SetControlExpression(3, "`" + devNunchuk + ":AccelX-`"); // Right
ncAccel->SetControlExpression(4, "`" + devNunchuk + ":AccelY-`"); // Forward
ncAccel->SetControlExpression(5, "`" + devNunchuk + ":AccelY+`"); // Backward
}
wmButtons->SetControlExpression(4, "Select"); // -
wmButtons->SetControlExpression(5, "Start"); // +
}

wmButtons->SetControlExpression(6, "R3"); // Home
Expand Down
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