Question

目前我的软件在MSCharts中使用了图表对象的HitTest()方法，但随着我将其扩展到我的图表上越来越多的数据点以及其他因素，这可能会对性能造成巨大影响。

我想知道是否有任何替代方法可以提供相同的功能（在图表上获取光标位置的X坐标）但没有性能命中，因为命中测试似乎是一种非常强大的获取方式我的回答。

我的图表是从班级System.Windows.Forms.DataVisualization.Charting.Chart

创建的

为清晰起见编辑：我需要在图表上找到一条线的位置，以便将其用于其他计算。

Answer 1

鼠标滚轮事件存在相同的性能问题。

这是我的解决方案：

获取当前鼠标位置的轴值：
```
double posX = Math.Round(currentArea.AxisX.PixelPositionToValue(e.X));
double posY = Math.Round(currentArea.AxisY.PixelPositionToValue(e.Y));
```
从Showing Mouse Axis Coordinates on Chart Control获取一点点改动以使其更准确。

但您应该先检查一下，鼠标是否在 ChartArea 中，否则会引发例外。

获取鼠标指向的ChatElement：

// Gets the ChartArea that the mouse points
private ChartArea mouseinChartArea(Chart source, Point e)
{
    double relativeX = (double)e.X * 100 / source.Width;
    double relativeY = (double)e.Y * 100 / source.Height;

    foreach (ChartArea ca in source.ChartAreas)
    {
        if (relativeX > ca.Position.X && relativeX < ca.Position.Right &&
            relativeY > ca.Position.Y && relativeY < ca.Position.Bottom)
            return ca;
    }
    return null;
}

// for my purpose, returns an axis. But you can return anything
private Axis findAxisforZooming(Chart source, Point e)
{
    ChartArea currentArea = mouseinChartArea(source, new Point(e.X, e.Y)); // Check if inside 
    if (currentArea == null)
        return null;

    double axisXfontSize = currentArea.AxisX.LabelAutoFitMinFontSize + ((double)source.Width / SystemInformation.PrimaryMonitorSize.Width)
        * (currentArea.AxisX.LabelAutoFitMaxFontSize - currentArea.AxisX.LabelAutoFitMinFontSize);
    double axisYfontSize = currentArea.AxisY.LabelAutoFitMinFontSize + ((double)source.Height / SystemInformation.PrimaryMonitorSize.Height)
        * (currentArea.AxisY.LabelAutoFitMaxFontSize - currentArea.AxisY.LabelAutoFitMinFontSize);
    double axisYfontHeightSize = (axisYfontSize - currentArea.AxisY.LabelStyle.Font.Size) + currentArea.AxisY.LabelStyle.Font.Height;

    Graphics g = this.CreateGraphics();
    if (currentArea.AxisX.LabelStyle.Font.Unit == GraphicsUnit.Point)
        axisXfontSize = axisXfontSize * g.DpiX / 72;
    if (currentArea.AxisY.LabelStyle.Font.Unit == GraphicsUnit.Point)
        axisYfontHeightSize = axisYfontHeightSize * g.DpiX / 72;
    g.Dispose();

    // Replacing the SystemInformation.PrimaryMonitorSize with the source.Width / Height will give the accurate TickMarks size.
    // But it doens't count for the gab between the tickMarks and the axis lables (so by replacing, it give a good proximity with the gab)
    int axisYTickMarks = (int)Math.Round(currentArea.AxisY.MajorTickMark.Size / 100 * SystemInformation.PrimaryMonitorSize.Width); // source.Width;
    int axisXTickMarks = (int)Math.Round(currentArea.AxisX.MajorTickMark.Size / 100 * SystemInformation.PrimaryMonitorSize.Height); // source.Height;

    int leftInnerPlot = (int)Math.Round(currentArea.Position.X / 100 * source.Width +
        currentArea.InnerPlotPosition.X / 100 * currentArea.Position.Width / 100 * source.Width);
    int rightInnerPlot = (int)Math.Round(currentArea.Position.X / 100 * this.chart1.Width +
        currentArea.InnerPlotPosition.Right / 100 * currentArea.Position.Width / 100 * source.Width);
    int topInnerPlot = (int)Math.Round(currentArea.Position.Y / 100 * this.chart1.Height +
        currentArea.InnerPlotPosition.Y / 100 * currentArea.Position.Height / 100 * source.Height);
    int bottomInnerPlot = (int)Math.Round(currentArea.Position.Y / 100 * source.Height +
        currentArea.InnerPlotPosition.Bottom / 100 * currentArea.Position.Height / 100 * source.Height);

    // Now you got the boundaries of every important ChartElement.
    // Only left to check if the mouse is within your desire ChartElement,
    // like the following:    

    bottomInnerPlot += axisXTickMarks + (int)Math.Round(axisXfontSize); // Include AxisX

    if (e.X > leftInnerPlot && e.X < rightInnerPlot &&
        e.Y > topInnerPlot && e.Y < bottomInnerPlot) // return AxisX if inside the InnerPlot area or on AxisX
        return currentArea.AxisX;
    else if (e.X > (leftInnerPlot - axisYTickMarks - (int)Math.Round(axisYfontHeightSize)) && e.X < rightInnerPlot &&
             e.Y > topInnerPlot && e.Y < bottomInnerPlot) // return AxisY if on AxisY only
        return currentArea.AxisY;

    return null;
}

可以看出，代码长于HitTest()。但运行时间更短。

HotTest（）的替代品

1 个答案: