add pinch to zoom support

app/src/main/kotlin/com/simplemobiletools/camera/helpers/PinchToZoomOnScaleGestureListener.kt

@@ -0,0 +1,19 @@
+package com.simplemobiletools.camera.helpers
+
+import android.view.ScaleGestureDetector
+import androidx.camera.core.CameraControl
+import androidx.camera.core.CameraInfo
+
+class PinchToZoomOnScaleGestureListener(
+    private val cameraInfo: CameraInfo,
+    private val cameraControl: CameraControl,
+) : ScaleGestureDetector.SimpleOnScaleGestureListener() {
+    private val zoomCalculator = ZoomCalculator()
+
+    override fun onScale(detector: ScaleGestureDetector): Boolean {
+        val zoomState = cameraInfo.zoomState.value ?: return false
+        val zoomRatio = zoomCalculator.calculateZoomRatio(zoomState, detector.scaleFactor)
+        cameraControl.setZoomRatio(zoomRatio)
+        return true
+    }
+}

app/src/main/kotlin/com/simplemobiletools/camera/helpers/ZoomCalculator.kt

@@ -0,0 +1,20 @@
+package com.simplemobiletools.camera.helpers
+
+import androidx.camera.core.ZoomState
+
+class ZoomCalculator {
+
+    fun calculateZoomRatio(zoomState: ZoomState, pinchToZoomScale: Float): Float {
+        val clampedRatio = zoomState.zoomRatio * speedUpZoomBy2X(pinchToZoomScale)
+        // Clamp the ratio with the zoom range.
+        return clampedRatio.coerceAtLeast(zoomState.minZoomRatio).coerceAtMost(zoomState.maxZoomRatio)
+    }
+
+    private fun speedUpZoomBy2X(scaleFactor: Float): Float {
+        return if (scaleFactor > 1f) {
+            1.0f + (scaleFactor - 1.0f) * 2
+        } else {
+            1.0f - (1.0f - scaleFactor) * 2
+        }
+    }
+}

app/src/main/kotlin/com/simplemobiletools/camera/implementations/CameraXPreview.kt

@@ -14,6 +14,7 @@ import android.view.GestureDetector
 import android.view.GestureDetector.SimpleOnGestureListener
 import android.view.MotionEvent
 import android.view.OrientationEventListener
+import android.view.ScaleGestureDetector
 import android.view.Surface
 import androidx.appcompat.app.AppCompatActivity
 import androidx.camera.core.*
@@ -44,6 +45,8 @@ import com.simplemobiletools.camera.extensions.config
 import com.simplemobiletools.camera.extensions.toAppFlashMode
 import com.simplemobiletools.camera.extensions.toCameraXFlashMode
 import com.simplemobiletools.camera.helpers.MediaSoundHelper
+import com.simplemobiletools.camera.helpers.PinchToZoomOnScaleGestureListener
+import com.simplemobiletools.camera.helpers.ZoomCalculator
 import com.simplemobiletools.camera.interfaces.MyPreview
 import com.simplemobiletools.commons.extensions.showErrorToast
 import com.simplemobiletools.commons.extensions.toast
@@ -280,6 +283,7 @@ class CameraXPreview(
     // source: https://stackoverflow.com/a/60095886/10552591
     private fun setupZoomAndFocus() {
         Log.i(TAG, "camera controller: ${previewView.controller}")
+        val scaleGesture = camera?.let { ScaleGestureDetector(activity, PinchToZoomOnScaleGestureListener(it.cameraInfo, it.cameraControl)) }
         val gestureDetector = GestureDetector(activity, object : SimpleOnGestureListener() {
             override fun onSingleTapConfirmed(event: MotionEvent): Boolean {
                 return camera?.cameraInfo?.let {
@@ -306,6 +310,7 @@ class CameraXPreview(
         previewView.setOnTouchListener { _, event ->
             Log.i(TAG, "setOnTouchListener: x=${event.x}, y=${event.y}")
             gestureDetector.onTouchEvent(event)
+            scaleGesture?.onTouchEvent(event)
             true
         }
     }