iOS15 specific recommended zoom factor (#58)

* feat: implement ios15 specfic recommended zoom factor

* style: remove debug log

* fix: variable typings

* feat: update refocus timer interval to 2seconds

Author: ian-wd

example/ios/Podfile.lock

@@ -218,7 +218,7 @@ PODS:
   - React-jsinspector (0.68.0)
   - React-logger (0.68.0):
     - glog
-  - react-native-idscan-sdk (0.5.1):
+  - react-native-idscan-sdk (0.7.0):
     - React-Core
   - React-perflogger (0.68.0)
   - React-RCTActionSheet (0.68.0):
@@ -413,7 +413,7 @@ SPEC CHECKSUMS:
   React-jsiexecutor: 010a66edf644339f6da72b34208b070089680415
   React-jsinspector: 90f0bfd5d04e0b066c29216a110ffb9a6c34f23f
   React-logger: 8474fefa09d05f573a13c044cb0dfd751d4e52e3
-  react-native-idscan-sdk: 10fcca037729c3c1f0213010599ceff6754a57d7
+  react-native-idscan-sdk: 51842760e288b24c1cc209994eeaf75ce7132363
   React-perflogger: 15cb741d6c2379f4d3fc8f9e4d4e1110ef3020cb
   React-RCTActionSheet: ea9099db0597bd769430db1e2d011fd5fdb7fc5e
   React-RCTAnimation: 252df4749866f2654f37612f839522cac91c1165
@@ -430,4 +430,4 @@ SPEC CHECKSUMS:
 
 PODFILE CHECKSUM: ab59e48bef4677d9d279df353a73581b0f9df2cd
 
-COCOAPODS: 1.11.3
+COCOAPODS: 1.12.0

ios/ScannerViewController.m

@@ -183,7 +183,7 @@ - (void)initCapture
     [MWOverlay addToPreviewLayer: self.prevLayer];
 #endif
 
-    self.focusTimer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(reFocus) userInfo:nil repeats:YES];
+    self.focusTimer = [NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(reFocus) userInfo:nil repeats:YES];
 
     [self CustomOverlay];
 }
@@ -382,7 +382,12 @@ - (void)dealloc {
 
 - (void) startScanning {
     self.state = LAUNCHING_CAMERA;
-    [self.captureSession startRunning];
+    
+    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+        [self.captureSession startRunning];
+        [self setRecommendedZoomFactor];
+    });
+    
     self.prevLayer.hidden = NO;
     self.state = CAMERA;
 }
@@ -413,6 +418,57 @@ - (void) deinitCapture {
     }
 }
 
+- (void) setRecommendedZoomFactor {
+    if (@available(iOS 15.0, *)) {
+        float deviceMinimumFocusDistance = [self.device minimumFocusDistance];
+        
+        if (deviceMinimumFocusDistance == -1) {
+            return;
+        }
+        
+        CMVideoDimensions formatDimensions = CMVideoFormatDescriptionGetDimensions([self.device.activeFormat formatDescription]);
+        float rectOfInterestWidth = (float)formatDimensions.height / (float)formatDimensions.width;
+        
+        float deviceFieldOfView = [self.device.activeFormat videoFieldOfView];
+        float minimumSubjectDistanceForCode = [self minimumSubjectDistanceForCode:deviceFieldOfView minimumCodeSize:20 previewFillPercentage:rectOfInterestWidth];
+        
+        if (minimumSubjectDistanceForCode < deviceMinimumFocusDistance) {
+            float zoomFactor = deviceMinimumFocusDistance / minimumSubjectDistanceForCode;
+            
+            @try {
+                NSError *error;
+                if ([self.device lockForConfiguration:&error]) {
+                    self.device.videoZoomFactor = zoomFactor;
+                    
+                    [self.device unlockForConfiguration];
+                }
+            }
+            @catch (id exceptionError) {
+                NSLog(@"Could not lock for configuration");
+            }
+        }
+    }
+}
+
+- (float) minimumSubjectDistanceForCode:(float)fieldOfView
+                        minimumCodeSize:(float)minimumCodeSize
+                  previewFillPercentage:(float)previewFillPercentage
+{
+    /*
+        Given the camera horizontal field of view, we can compute the distance (mm) to make a code
+        of minimumCodeSize (mm) fill the previewFillPercentage.
+     */
+    float fieldOfViewDivided = fieldOfView / 2;
+    float radians = [self degreesToRadians: fieldOfViewDivided];
+    float filledCodeSize = minimumCodeSize / previewFillPercentage;
+    
+    return filledCodeSize / tan(radians);
+}
+
+- (float) degreesToRadians:(float)degrees
+{
+    return degrees * M_PI / 180;
+}
 
 - (void)decodeResultNotification: (NSNotification *)notification {