Gyro and Accel sensor support for Switch Pro Controller.

Note that axes are changed to match the axes we're using with PlayStation controllers, since users will appreciate consistent behaviour across devices.

src/joystick/hidapi/SDL_hidapi_switch.c

@@ -52,6 +52,9 @@
 /* How often you have to refresh a long duration rumble to keep the motors running */
 #define RUMBLE_REFRESH_FREQUENCY_MS 40
 
+#define SWITCH_GYRO_SCALE      14.2842f
+#define SWITCH_ACCEL_SCALE     4096.f
+
 typedef enum {
     k_eSwitchInputReportIDs_SubcommandReply       = 0x21,
     k_eSwitchInputReportIDs_FullControllerState   = 0x30,
@@ -220,6 +223,8 @@ typedef struct {
     SDL_bool m_bRumblePending;
     SDL_bool m_bRumbleZeroPending;
     Uint32 m_unRumblePending;
+    SDL_bool m_bHasSensors;
+    SDL_bool m_bReportSensors;
 
     SwitchInputOnlyControllerStatePacket_t m_lastInputOnlyState;
     SwitchSimpleStatePacket_t m_lastSimpleState;
@@ -550,6 +555,12 @@ static SDL_bool SetSlotLED(SDL_DriverSwitch_Context *ctx, Uint8 slot)
     return WriteSubcommand(ctx, k_eSwitchSubcommandIDs_SetPlayerLights, &led_data, sizeof(led_data), NULL);
 }
 
+static SDL_bool SetIMUEnabled(SDL_DriverSwitch_Context* ctx, SDL_bool enabled)
+{
+    Uint8 imu_data = enabled ? 1 : 0;
+    return WriteSubcommand(ctx, k_eSwitchSubcommandIDs_EnableIMU, &imu_data, sizeof(imu_data), NULL);
+}
+
 static SDL_bool LoadStickCalibration(SDL_DriverSwitch_Context *ctx, Uint8 input_mode)
 {
     Uint8 *pStickCal;
@@ -761,6 +772,12 @@ HIDAPI_DriverSwitch_OpenJoystick(SDL_HIDAPI_Device *device, SDL_Joystick *joysti
             device->product_id == USB_PRODUCT_NINTENDO_SWITCH_PRO) {
             input_mode = k_eSwitchInputReportIDs_FullControllerState;
         }
+        
+        if (input_mode == k_eSwitchInputReportIDs_FullControllerState) {
+            SDL_PrivateJoystickAddSensor(joystick, SDL_SENSOR_GYRO);
+            SDL_PrivateJoystickAddSensor(joystick, SDL_SENSOR_ACCEL);
+            ctx->m_bHasSensors = SDL_TRUE;
+        }
 
         if (!LoadStickCalibration(ctx, input_mode)) {
             SDL_SetError("Couldn't load stick calibration");
@@ -945,7 +962,30 @@ HIDAPI_DriverSwitch_SetJoystickLED(SDL_HIDAPI_Device *device, SDL_Joystick *joys
 static int
 HIDAPI_DriverSwitch_SetJoystickSensorsEnabled(SDL_HIDAPI_Device *device, SDL_Joystick *joystick, SDL_bool enabled)
 {
-    return SDL_Unsupported();
+    SDL_DriverSwitch_Context* ctx = (SDL_DriverSwitch_Context*)device->context;
+    
+    if (!ctx->m_bHasSensors) {
+        return SDL_Unsupported();
+    }
+
+    SetIMUEnabled(ctx, enabled);
+    ctx->m_bReportSensors = enabled;
+
+    return 0;
+}
+
+static float
+HIDAPI_DriverSwitch_ScaleGyro(Sint16 value)
+{
+    float result = (value / SWITCH_GYRO_SCALE) * (float)M_PI / 180.0f;
+    return result;
+}
+
+static float
+HIDAPI_DriverSwitch_ScaleAccel(Sint16 value)
+{
+    float result = (value / SWITCH_ACCEL_SCALE) * SDL_STANDARD_GRAVITY;
+    return result;
 }
 
 static void HandleInputOnlyControllerState(SDL_Joystick *joystick, SDL_DriverSwitch_Context *ctx, SwitchInputOnlyControllerStatePacket_t *packet)
@@ -1210,6 +1250,42 @@ static void HandleFullControllerState(SDL_Joystick *joystick, SDL_DriverSwitch_C
         }
     }
 
+    if (ctx->m_bReportSensors) {
+        float data[3];
+
+        /* Note the order of components has been shuffled to match PlayStation controllers,
+         * since that's our de facto standard from already supporting those controllers, and
+         * users will want consistent axis mappings across devices.
+         */
+        data[0] = HIDAPI_DriverSwitch_ScaleGyro(packet->imuState[0].sGyroY);
+        data[1] = HIDAPI_DriverSwitch_ScaleGyro(packet->imuState[0].sGyroZ);
+        data[2] = HIDAPI_DriverSwitch_ScaleGyro(packet->imuState[0].sGyroX);
+        data[0] += HIDAPI_DriverSwitch_ScaleGyro(packet->imuState[1].sGyroY);
+        data[1] += HIDAPI_DriverSwitch_ScaleGyro(packet->imuState[1].sGyroZ);
+        data[2] += HIDAPI_DriverSwitch_ScaleGyro(packet->imuState[1].sGyroX);
+        data[0] += HIDAPI_DriverSwitch_ScaleGyro(packet->imuState[2].sGyroY);
+        data[1] += HIDAPI_DriverSwitch_ScaleGyro(packet->imuState[2].sGyroZ);
+        data[2] += HIDAPI_DriverSwitch_ScaleGyro(packet->imuState[2].sGyroX);
+        data[0] /= -3.f;
+        data[1] /= 3.f;
+        data[2] /= -3.f;
+        SDL_PrivateJoystickSensor(joystick, SDL_SENSOR_GYRO, data, 3);
+
+        data[0] = HIDAPI_DriverSwitch_ScaleAccel(packet->imuState[0].sAccelY);
+        data[1] = HIDAPI_DriverSwitch_ScaleAccel(packet->imuState[0].sAccelZ);
+        data[2] = HIDAPI_DriverSwitch_ScaleAccel(packet->imuState[0].sAccelX);
+        data[0] += HIDAPI_DriverSwitch_ScaleAccel(packet->imuState[1].sAccelY);
+        data[1] += HIDAPI_DriverSwitch_ScaleAccel(packet->imuState[1].sAccelZ);
+        data[2] += HIDAPI_DriverSwitch_ScaleAccel(packet->imuState[1].sAccelX);
+        data[0] += HIDAPI_DriverSwitch_ScaleAccel(packet->imuState[2].sAccelY);
+        data[1] += HIDAPI_DriverSwitch_ScaleAccel(packet->imuState[2].sAccelZ);
+        data[2] += HIDAPI_DriverSwitch_ScaleAccel(packet->imuState[2].sAccelX);
+        data[0] /= -3.f;
+        data[1] /= 3.f;
+        data[2] /= -3.f;
+        SDL_PrivateJoystickSensor(joystick, SDL_SENSOR_ACCEL, data, 3);
+    }
+
     ctx->m_lastFullState = *packet;
 }