app/resources/qml/Pages/QrCodeScanPage.qml

import QtQuick 2.0
import QtQuick.Controls 2.12
import QtQuick.Layouts 1.12
import QZXing 3.3
import QtMultimedia 5.12
import QtQuick.Shapes 1.12
import QtQuick.Controls.Material 2.12

import "../Components"

Page {
    id: control

    property string _statusText: ""
    property string _statusColor: Material.primaryTextColor
    property bool _freezeScanning: false
    signal headerComponentChanged()

    //% "Scan QR-Code"
    title: qsTrId("#scanQrCode")

    onFocusChanged: focus ? open() : close()

    function open() {
        _setDefaultStatusText()
        control._freezeScanning = false
        if(serverConn.isCameraPermissionGranted())
            cameraLoader.sourceComponent = cameraComponent
        else
            cameraLoader.sourceComponent = noPermissionComponent
    }

    function close() {
        cameraLoader.sourceComponent = null
    }

    function _setDefaultStatusText() {
        //% "Place the Code in the center"
        _statusText = qsTrId("#placeQrCodeInCenter")
        _statusColor = Material.primaryTextColor
    }

    function _handleTag(tag) {
        if(control._freezeScanning)
            return

        control._freezeScanning = true

        //% "Plase wait"
        control._statusText = qsTrId("#pleaseWait") + "..."

        if(app.openWidgetFromUrl(tag))
            control.close()
        else {
            //% "Invalid QR-Code"
            control._statusText = qsTrId("#invalidQrCode")
            control._statusColor = Material.color(Material.Red)
            statusTextResetTimer.start()
            control._freezeScanning = false
        }
    }

    function _requestCameraPermission() {
        var permissionGranted = serverConn.requestCameraPermission()

        if(permissionGranted)
            cameraLoader.sourceComponent = cameraComponent
    }

    contentItem: Loader {
        id: cameraLoader

        anchors.fill: parent

        //asynchronous: true
        sourceComponent: null
    }

    Component {
        id: cameraComponent
        Item {
            anchors.fill: parent

            Camera {
                id: camera
                captureMode: Camera.CaptureStillImage
                imageProcessing.whiteBalanceMode: CameraImageProcessing.WhiteBalanceAuto

                focus {
                    focusMode: Camera.FocusContinuous
                    focusPointMode: Camera.FocusPointCenter
                }
            }

            FancyBusyIndicator {
                anchors.centerIn: parent
            }

            VideoOutput {
                id: videoOutput
                x: 0
                y: 0
                width: parent.width
                height: parent.height

                fillMode: VideoOutput.PreserveAspectCrop

                source: camera
                filters: [ zxingFilter ]
                focus : visible // to receive focus and capture key events when visible

                autoOrientation: true

                MouseArea {
                    anchors.fill: parent

                    onClicked: {
                        if (camera.lockStatus !== Camera.Unlocked)
                            camera.unlock();

                        camera.searchAndLock();
                    }
                }

                Rectangle {
                    anchors {
                        top: parent.top
                        left: parent.left
                        right: app.landscape() ? focusIndicatorRect.left : parent.right
                        bottom: app.landscape() ? parent.bottom : focusIndicatorRect.top
                    }

                    opacity: focusIndicatorRect.opacity
                    color: focusIndicatorRect.border.color
                }

                Rectangle {
                    id: focusIndicatorRect
                    anchors.centerIn: parent

                    width: Math.min(parent.height, parent.width)
                    height: width

                    border.width: width * 0.1
                    border.color: "#000000"

                    opacity: 0.5
                    color: "transparent"
                }

                Rectangle {
                    anchors {
                        bottom: focusIndicatorRect.bottom
                        bottomMargin: height * 0.5
                        horizontalCenter: focusIndicatorRect.horizontalCenter
                    }

                    width: (focusIndicatorRect.width - focusIndicatorRect.border.width * 2) * 0.8
                    height: focusIndicatorRect.border.width

                    radius: height * 0.3

                    color: Material.backgroundColor

                    Material.elevation: 10


                    Label {
                        anchors {
                            fill: parent
                            margins: height * 0.1
                        }

                        color: control._statusColor

                        font.pixelSize: height * 0.5
                        fontSizeMode: Text.Fit
                        minimumPixelSize: height * 0.2

                        verticalAlignment: Text.AlignVCenter
                        horizontalAlignment: Text.AlignHCenter

                        text: control._statusText
                    }
                }

                Rectangle {
                    anchors {
                        top: app.landscape() ? parent.top : focusIndicatorRect.bottom
                        left: app.landscape() ? focusIndicatorRect.right : parent.left
                        right: parent.right
                        bottom: parent.bottom
                    }

                    opacity: focusIndicatorRect.opacity
                    color: focusIndicatorRect.border.color
                }
            }
        }
    }

    Component {
        id: noPermissionComponent
        ColumnLayout {
            //anchors.fill: parent
            //anchors.margins: app.landscape() ? app.height * 0.1 : app.width * 0.1

            property int columnWidth: control.width * 0.9

            spacing: height * 0.02

            Item {
                Layout.fillHeight: true
            }

            Label {
                id: noPermissionIcon

                Layout.preferredWidth: parent.columnWidth
                Layout.alignment: Layout.Center

                font.pixelSize: app.landscape() ? parent.height * 0.25:parent.height * 0.15
                font.family: fa5solid.name

                horizontalAlignment: Text.AlignHCenter

                text: "\uf3ed"
            }
            Label {
                id: noPermissionText

                Layout.preferredWidth: parent.columnWidth
                Layout.alignment: Layout.Center

                font.bold: true
                font.pixelSize: noPermissionIcon.height * 0.2

                horizontalAlignment: Text.AlignHCenter

                wrapMode: Text.Wrap

                //% "Camera access required"
                text: qsTrId("#cameraPermissionDenied")
            }

            Label {
                id: noPermissionDetailText

                Layout.preferredWidth: parent.columnWidth
                Layout.alignment: Layout.Center

                font.pixelSize: noPermissionText.font.pixelSize * 0.7

                horizontalAlignment: Text.AlignHCenter

                wrapMode: Text.Wrap

                //% "blueROCK needs to access your camera in order to scan QR-Codes. It will never record or store any photos or videos."
                text: qsTrId("#cameraPermissionDeniedDetails")
            }

            Button {
                id: grantPermissionButton

                Layout.alignment: Layout.Center

                //% "Allow access"
                text: qsTrId("#allowAccess")

                onClicked: control._requestCameraPermission()
            }


            Item {
                Layout.fillHeight: true
            }

        }
    }

    QZXingFilter {
        id: zxingFilter

        decoder {
            onTagFound: control._handleTag(tag)

            enabledDecoders: QZXing.DecoderFormat_QR_CODE
        }
    }

    Timer {
        id: statusTextResetTimer
        running: false
        repeat: false
        interval: 3000
        onTriggered: _setDefaultStatusText()
    }
}