用QML写一个折线图控件，横坐标单位为时间，纵坐标数值，该控件可以通过手指进行缩放，从而调整横纵坐标比例重新显示

以下是一个简单的QML折线图控件示例，可以通过手指进行缩放，并且可以根据缩放比例重新计算横纵坐标的范围。

import QtQuick 2.15
import QtCharts 2.3

ChartView {
    id: chartView
    title: "折线图"
    antialiasing: true
    animationOptions: ChartView.AllAnimations
    legend.visible: false
    margins.left: 0
    margins.right: 0
    margins.top: 0
    margins.bottom: 0

    property real zoomFactor: 1.0
    property bool isPinching: false
    property point lastPos: Qt.point(0, 0)
    property real minX: 0
    property real maxX: 10
    property real minY: 0
    property real maxY: 100

    function updateRange() {
        var xRange = maxX - minX
        var yRange = maxY - minY
        var xRatio = chartView.width / xRange / zoomFactor
        var yRatio = chartView.height / yRange / zoomFactor
        chartView.axisX.min = minX - (chartView.width / xRatio - xRange) / 2
        chartView.axisX.max = maxX + (chartView.width / xRatio - xRange) / 2
        chartView.axisY.min = minY - (chartView.height / yRatio - yRange) / 2
        chartView.axisY.max = maxY + (chartView.height / yRatio - yRange) / 2
    }

    LineSeries {
        id: lineSeries
        XYPoint { x: 0; y: 50 }
        XYPoint { x: 1; y: 60 }
        XYPoint { x: 2; y: 40 }
        XYPoint { x: 3; y: 70 }
        XYPoint { x: 4; y: 30 }
        XYPoint { x: 5; y: 80 }
        XYPoint { x: 6; y: 20 }
        XYPoint { x: 7; y: 90 }
        XYPoint { x: 8; y: 10 }
        XYPoint { x: 9; y: 100 }
    }

    AreaSeries {
        id: areaSeries
        useOpenGL: true
        borderColor: "transparent"
        brush.gradient: Gradient {
            GradientStop { position: 0; color: "steelblue" }
            GradientStop { position: 1; color: "transparent" }
        }
        XYPoint { x: 0; y: 50 }
        XYPoint { x: 1; y: 60 }
        XYPoint { x: 2; y: 40 }
        XYPoint { x: 3; y: 70 }
        XYPoint { x: 4; y: 30 }
        XYPoint { x: 5; y: 80 }
        XYPoint { x: 6; y: 20 }
        XYPoint { x: 7; y: 90 }
        XYPoint { x: 8; y: 10 }
        XYPoint { x: 9; y: 100 }
    }

    Component.onCompleted: {
        updateRange()
    }

    onPinchStarted: {
        isPinching = true
    }

    onPinchUpdated: {
        var factor = event.scale / chartView.zoomFactor
        chartView.zoomFactor = event.scale
        chartView.axisX.min = chartView.axisX.min + (event.center.x - chartView.width / 2) / chartView.width * (maxX - minX) / factor
        chartView.axisX.max = chartView.axisX.max - (chartView.width / 2 - event.center.x) / chartView.width * (maxX - minX) / factor
        chartView.axisY.min = chartView.axisY.min + (event.center.y - chartView.height / 2) / chartView.height * (maxY - minY) / factor
        chartView.axisY.max = chartView.axisY.max - (chartView.height / 2 - event.center.y) / chartView.height * (maxY - minY) / factor
    }

    onPinchFinished: {
        isPinching = false
    }

    onPositionChanged: {
        if (isPinching) {
            var deltaX = event.position.x - lastPos.x
            var deltaY = event.position.y - lastPos.y
            chartView.axisX.min = chartView.axisX.min - deltaX / chartView.width * (maxX - minX) / chartView.zoomFactor
            chartView.axisX.max = chartView.axisX.max - deltaX / chartView.width * (maxX - minX) / chartView.zoomFactor
            chartView.axisY.min = chartView.axisY.min + deltaY / chartView.height * (maxY - minY) / chartView.zoomFactor
            chartView.axisY.max = chartView.axisY.max + deltaY / chartView.height * (maxY - minY) / chartView.zoomFactor
        }
        lastPos = event.position
    }

    onWidthChanged: {
        updateRange()
    }

    onHeightChanged: {
        updateRange()
    }

    Axes {
        id: axes
        horizontalAxis: ValueAxis {
            id: valueAxisX
            min: chartView.minX
            max: chartView.maxX
            labelFormat: "%.1f"
            tickCount: 11
        }
        verticalAxis: ValueAxis {
            id: valueAxisY
            min: chartView.minY
            max: chartView.maxY
            labelFormat: "%.0f"
            tickCount: 11
        }
    }
}

该控件主要通过`ChartView`和`ValueAxis`组件实现，其中`LineSeries`和`AreaSeries`用于绘制折线和填充区域。控件定义了`zoomFactor`、`isPinching`、`lastPos`、`minX`、`maxX`、`minY`和`maxY`等属性，通过`onPinchStarted`、`onPinchUpdated`和`onPinchFinished`处理手指缩放的事件，通过`onPositionChanged`处理手指拖拽的事件，在每次缩放或拖拽后重新计算横纵坐标范围，并更新`ValueAxis`的`min`和`max`属性。