function startCameraPreview()

in src/windows/CameraProxy.js [343:437]
67 lines of code
11 McCabe index (conditional complexity)

    function startCameraPreview () {
        // Search for available camera devices
        // This is necessary to detect which camera (front or back) we should use
        var DeviceEnum = Windows.Devices.Enumeration;
        var expectedPanel = cameraDirection === 1 ? DeviceEnum.Panel.front : DeviceEnum.Panel.back;

        // Add focus event handler to capture the event when user suspends the app and comes back while the preview is on
        window.addEventListener('focus', continueVideoOnFocus);

        DeviceEnum.DeviceInformation.findAllAsync(DeviceEnum.DeviceClass.videoCapture).then(function (devices) {
            if (devices.length <= 0) {
                destroyCameraPreview();
                errorCallback('Camera not found');
                return;
            }

            devices.forEach(function (currDev) {
                if (currDev.enclosureLocation.panel && currDev.enclosureLocation.panel === expectedPanel) {
                    captureSettings.videoDeviceId = currDev.id;
                }
            });

            captureSettings.photoCaptureSource = Windows.Media.Capture.PhotoCaptureSource.photo;

            return capture.initializeAsync(captureSettings);
        }).then(function () {
            // create focus control if available
            var VideoDeviceController = capture.videoDeviceController;
            var FocusControl = VideoDeviceController.focusControl;

            if (FocusControl.supported === true) {
                capturePreview.addEventListener('click', function () {
                    // Make sure function isn't called again before previous focus is completed
                    if (this.getAttribute('clicked') === '1') {
                        return false;
                    } else {
                        this.setAttribute('clicked', '1');
                    }
                    var preset = Windows.Media.Devices.FocusPreset.autoNormal;
                    var parent = this;
                    FocusControl.setPresetAsync(preset).done(function () {
                        // set the clicked attribute back to '0' to allow focus again
                        parent.setAttribute('clicked', '0');
                    });
                });
            }

            // msdn.microsoft.com/en-us/library/windows/apps/hh452807.aspx
            capturePreview.msZoom = true;
            capturePreview.src = URL.createObjectURL(capture);
            capturePreview.play();

            // Bind events to controls
            sensor = Windows.Devices.Sensors.SimpleOrientationSensor.getDefault();
            if (sensor !== null) {
                sensor.addEventListener('orientationchanged', onOrientationChange);
            }

            // add click events to capture and cancel buttons
            cameraCaptureButton.addEventListener('click', onCameraCaptureButtonClick);
            cameraCancelButton.addEventListener('click', onCameraCancelButtonClick);

            // Change default orientation
            if (sensor) {
                setPreviewRotation(sensor.getCurrentOrientation());
            } else {
                setPreviewRotation(Windows.Graphics.Display.DisplayInformation.getForCurrentView().currentOrientation);
            }

            // Get available aspect ratios
            var aspectRatios = getAspectRatios(capture);

            // Couldn't find a good ratio
            if (aspectRatios.length === 0) {
                destroyCameraPreview();
                errorCallback('There\'s not a good aspect ratio available');
                return;
            }

            // add elements to body
            document.body.appendChild(capturePreview);
            document.body.appendChild(cameraCaptureButton);
            document.body.appendChild(cameraCancelButton);

            if (aspectRatios.indexOf(DEFAULT_ASPECT_RATIO) > -1) {
                return setAspectRatio(capture, DEFAULT_ASPECT_RATIO);
            } else {
                // Doesn't support 16:9 - pick next best
                return setAspectRatio(capture, aspectRatios[0]);
            }
        }).done(null, function (err) {
            destroyCameraPreview();
            errorCallback('Camera intitialization error ' + err);
        });
    }