feat: Add CameraDevice.maxTorchStrength prop

apps/simple-camera/__tests__/visioncamera.controller.harness.ts

@@ -133,9 +133,6 @@ describe('VisionCamera - Controller', () => {
     await session.start()
 
     try {
-      // TODO: Add setTorchMode('on', STRENGTH) test when we expose something like
-      //       CameraDevice.supportsTorchStrength - currently this might throw on
-      //       some phones without a way to check upfront if it supports setting strength!
       await controller.setTorchMode('on')
       expect(controller.torchMode).toBe('on')
 
@@ -146,6 +143,46 @@ describe('VisionCamera - Controller', () => {
     }
   })
 
+  it('sets torchMode with a specific strength when the device supports it', async () => {
+    if (backDevice.maxTorchStrength === 0) {
+      console.log(
+        '[SKIP] torchStrength: device only supports binary torch (maxTorchStrength === 0)',
+      )
+      return
+    }
+    const session = await VisionCamera.createCameraSession(false)
+    const photoOutput = VisionCamera.createPhotoOutput({
+      targetResolution: CommonResolutions.HD_4_3,
+      containerFormat: 'jpeg',
+      quality: 0.8,
+      qualityPrioritization: 'balanced',
+    })
+    const [controller] = await session.configure([
+      {
+        input: backDevice,
+        outputs: [{ output: photoOutput, mirrorMode: 'auto' }],
+        constraints: [],
+      },
+    ])
+    if (controller == null) throw new Error('no controller')
+    await session.start()
+
+    try {
+      const target = backDevice.maxTorchStrength / 2
+      await controller.setTorchMode('on', target)
+      expect(controller.torchMode).toBe('on')
+      expect(controller.torchStrength).toBeGreaterThan(0)
+      expect(controller.torchStrength).toBeLessThanOrEqual(
+        backDevice.maxTorchStrength,
+      )
+
+      await controller.setTorchMode('off')
+      expect(controller.torchMode).toBe('off')
+    } finally {
+      await session.stop()
+    }
+  })
+
   it('sets exposure bias to min/max when the device supports it', async () => {
     if (!backDevice.supportsExposureBias) {
       console.log('[SKIP] exposureBias: not supported on this device')

packages/react-native-vision-camera/android/src/main/java/com/margelo/nitro/camera/hybrids/inputs/HybridCameraDevice.kt

@@ -168,6 +168,14 @@ class HybridCameraDevice(
 
   override val hasTorch: Boolean
     get() = cameraInfo.hasFlashUnit()
+  override val maxTorchStrength: Double
+    // CameraX reports `maxTorchStrengthLevel == 1` for devices that only
+    // support binary torch (on/off) and `> 1` for devices that accept a
+    // strength level. Our public `setTorchMode(mode, strength?)` API
+    // normalizes the incoming strength to 0..1 before multiplying by
+    // `maxTorchStrengthLevel`, so the public maximum is always `1.0`
+    // when strength is configurable, and `0.0` otherwise.
+    get() = if (cameraInfo.maxTorchStrengthLevel > 1) 1.0 else 0.0
 
   override val supportsLowLightBoost: Boolean
     get() = cameraInfo.isLowLightBoostSupported

packages/react-native-vision-camera/android/src/main/java/com/margelo/nitro/camera/hybrids/inputs/HybridPhysicalCameraDevice.kt

@@ -90,6 +90,7 @@ class HybridPhysicalCameraDevice(
   override val maxWhiteBalanceGain: Double = 0.0
   override val hasFlash: Boolean = false
   override val hasTorch: Boolean = false
+  override val maxTorchStrength: Double = 0.0
   override val supportsLowLightBoost: Boolean = false
   override val minZoom: Double = 0.0
   override val maxZoom: Double = 0.0

packages/react-native-vision-camera/ios/Hybrid Objects/Inputs/HybridCameraDevice.swift

@@ -195,6 +195,13 @@ final class HybridCameraDevice: HybridCameraDeviceSpec, NativeCameraDevice {
     return device.hasTorch
   }
 
+  var maxTorchStrength: Double {
+    // AVCaptureDevice.maxAvailableTorchLevel is a platform constant (1.0).
+    // When the device has a torch, torch strength is always configurable via
+    // setTorchModeOn(level:) in the 0...1 range.
+    return device.hasTorch ? Double(AVCaptureDevice.maxAvailableTorchLevel) : 0.0
+  }
+
   var supportsLowLightBoost: Bool {
     return device.isLowLightBoostSupported
   }

packages/react-native-vision-camera/src/specs/inputs/CameraDevice.nitro.ts

@@ -492,6 +492,21 @@ export interface CameraDevice
    * @see {@linkcode CameraController.setTorchMode | setTorchMode(...)}
    */
   readonly hasTorch: boolean
+  /**
+   * The maximum `strength` value accepted by
+   * {@linkcode CameraController.setTorchMode | setTorchMode('on', strength)}.
+   *
+   * - `0` — Configurable torch strength is **not supported** on this device.
+   * You may still call {@linkcode CameraController.setTorchMode | setTorchMode('on')}
+   * / `setTorchMode('off')` to toggle the torch, but passing a specific
+   * {@linkcode CameraController.setTorchMode | strength} value is not supported
+   * and will throw.
+   * - `> 0` — Strength is configurable in the normalized range
+   * from `0` (off) to `maxTorchStrength` (brightest).
+   *
+   * @see {@linkcode CameraController.setTorchMode | setTorchMode(...)}
+   */
+  readonly maxTorchStrength: number
 
   // pragma MARK: Low Light Boost
   /**