More documentation for CameraX (#423)

* Call CameraSession.Events.onCameraClosed when session stops

* Documentation for ScaleZoomHelper

* Rename getCameraProvider to createCameraProvider to clarify behavior

@@ -20,11 +20,44 @@ import android.content.Context
 import android.view.ScaleGestureDetector
 import android.view.ScaleGestureDetector.SimpleOnScaleGestureListener
 import androidx.camera.core.Camera
+import androidx.camera.core.CameraControl
+import io.livekit.android.camerax.ui.ScaleZoomHelper.Companion.createGestureDetector
 import io.livekit.android.room.track.LocalVideoTrack
 import io.livekit.android.util.LKLog
 import kotlinx.coroutines.flow.StateFlow
 import livekit.org.webrtc.getCameraX
 
+/**
+ * A helper class that handles zoom for a CameraX video capturer.
+ *
+ * For view based apps, [createGestureDetector] can be used to create a
+ * GestureDetector that attaches to your views to provide pinch-to-zoom
+ * functionality.
+ *
+ * For compose based apps, similar functionality can be implemented using
+ * Modifier.pointerInput:
+ *
+ * ```
+ * val scaleZoomHelper = remember(room, videoTrack) {
+ *     if (videoTrack is LocalVideoTrack) {
+ *         ScaleZoomHelper(videoTrack)
+ *     } else {
+ *         null
+ *     }
+ * }
+ *
+ * VideoRenderer(
+ *     modifier = modifier
+ *         .pointerInput(Unit) {
+ *             detectTransformGestures(
+ *                 onGesture = { _, _, zoom, _ ->
+ *                     scaleZoomHelper.zoom(zoom)
+ *                 },
+ *             )
+ *         },
+ * )
+ * ```
+ */
 class ScaleZoomHelper(
     private val cameraFlow: StateFlow<Camera?>?,
 ) {
@@ -32,10 +65,19 @@ class ScaleZoomHelper(
 
     init {
         if (cameraFlow != null) {
-            LKLog.w { "null camera flow passed in to ScaleZoomHelper, zoom is disabled." }
+            LKLog.i { "null camera flow passed in to ScaleZoomHelper, zoom is disabled." }
         }
     }
 
+    /**
+     * Scales the current zoom value by [factor].
+     *
+     * This method handles clamping the resulting zoom value to within the camera's
+     * minimum and maximum zoom. Best used with a scale gesture detector.
+     *
+     * @see CameraControl.setZoomRatio
+     * @see createGestureDetector
+     */
     fun zoom(factor: Float) {
         val camera = cameraFlow?.value ?: return
         val zoomState = camera.cameraInfo.zoomState.value ?: return
@@ -48,10 +90,35 @@ class ScaleZoomHelper(
     }
 
     companion object {
+
+        /**
+         * Creates a ScaleGestureDetector that can be used with a view to provide pinch-to-zoom functionality.
+         *
+         * Example:
+         * ```
+         * val scaleGestureDetector = ScaleZoomHelper.createGestureDetector(viewBinding.renderer.context, localVideoTrack)
+         * viewBinding.renderer.setOnTouchListener { _, event ->
+         *     scaleGestureDetector?.onTouchEvent(event)
+         *     return@setOnTouchListener true
+         * }
+         * ```
+         */
         fun createGestureDetector(context: Context, localVideoTrack: LocalVideoTrack): ScaleGestureDetector {
             return createGestureDetector(context, localVideoTrack.capturer.getCameraX())
         }
 
+        /**
+         * Creates a ScaleGestureDetector that can be used with a view to provide pinch-to-zoom functionality.
+         *
+         * Example:
+         * ```
+         * val scaleGestureDetector = ScaleZoomHelper.createGestureDetector(viewBinding.renderer.context, localVideoTrack)
+         * viewBinding.renderer.setOnTouchListener { _, event ->
+         *     scaleGestureDetector?.onTouchEvent(event)
+         *     return@setOnTouchListener true
+         * }
+         * ```
+         */
         fun createGestureDetector(context: Context, cameraFlow: StateFlow<Camera?>?): ScaleGestureDetector {
             val helper = ScaleZoomHelper(cameraFlow)
 

@@ -29,12 +29,14 @@ class CameraXHelper {
     companion object {
 
         /**
-         * Gets a CameraProvider that uses CameraX for its sessions.
+         * Creates a CameraProvider that uses CameraX for its sessions.
          *
          * For use with [CameraCapturerUtils.registerCameraProvider].
+         * Remember to unregister the provider when outside the lifecycle
+         * of [lifecycleOwner].
          */
         @ExperimentalCamera2Interop
-        fun getCameraProvider(
+        fun createCameraProvider(
             lifecycleOwner: LifecycleOwner,
         ) = object : CameraCapturerUtils.CameraProvider {
 

@@ -24,13 +24,13 @@ import android.hardware.camera2.CameraMetadata.CONTROL_VIDEO_STABILIZATION_MODE_
 import android.hardware.camera2.CameraMetadata.LENS_OPTICAL_STABILIZATION_MODE_OFF
 import android.hardware.camera2.CameraMetadata.LENS_OPTICAL_STABILIZATION_MODE_ON
 import android.hardware.camera2.CaptureRequest
+import android.os.Handler
 import android.util.Range
 import android.util.Size
 import android.view.Surface
 import androidx.camera.camera2.interop.Camera2CameraInfo
 import androidx.camera.camera2.interop.Camera2Interop
 import androidx.camera.core.Camera
-import androidx.camera.core.CameraControl
 import androidx.camera.core.CameraSelector
 import androidx.camera.core.ImageAnalysis
 import androidx.camera.core.Preview
@@ -60,7 +60,7 @@ internal constructor(
 ) : CameraSession {
 
     private var state = SessionState.RUNNING
-    private var cameraThreadHandler = surfaceTextureHelper.handler
+    private var cameraThreadHandler: Handler = surfaceTextureHelper.handler
     private lateinit var cameraProvider: ProcessCameraProvider
     private lateinit var surfaceProvider: SurfaceProvider
     var camera: Camera? = null
@@ -228,9 +228,12 @@ internal constructor(
 
         ContextCompat.getMainExecutor(context).execute {
             cameraProvider.unbindAll()
-        }
+            cameraThreadHandler.postAtFrontOfQueue {
+                events.onCameraClosed(this)
                 Logging.d(TAG, "Stop done")
             }
+        }
+    }
 
     private fun reportError(error: String) {
         checkIsOnCameraThread()
@@ -311,8 +314,4 @@ internal constructor(
     internal enum class StabilizationMode {
         OPTICAL, VIDEO, NONE
     }
-
-    interface CameraControlListener {
-        fun onCameraControlAvailable(control: CameraControl)
-    }
 }

@@ -147,7 +147,7 @@ class CallViewModel(
 
     init {
 
-        CameraXHelper.getCameraProvider(ProcessLifecycleOwner.get()).let {
+        CameraXHelper.createCameraProvider(ProcessLifecycleOwner.get()).let {
             if (it.isSupported(application)) {
                 CameraCapturerUtils.registerCameraProvider(it)
                 cameraProvider = it

@@ -31,8 +31,17 @@ import io.livekit.android.room.track.Track
 import io.livekit.android.room.track.VideoTrack
 import io.livekit.android.sample.databinding.ParticipantItemBinding
 import io.livekit.android.util.flow
-import kotlinx.coroutines.*
-import kotlinx.coroutines.flow.*
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.cancel
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.collectLatest
+import kotlinx.coroutines.flow.flatMapLatest
+import kotlinx.coroutines.flow.flowOf
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.launch
 
 class ParticipantItem(
     private val room: Room,