Winforms饼图图例文本的长度会影响标签和图表的大小

Question

我设置了以下ChartArea注释设置：

private void chart1_PrePaint(object sender, ChartPaintEventArgs e)
        {
            if (e.ChartElement is ChartArea)
            {
                var ta = new TextAnnotation();
                ta.IsMultiline = true;
                ta.Text = "Results of Calculation\n%";
                ta.Width = e.Position.Width;
                ta.Height = e.Position.Height;
                ta.X = e.Position.X;
                ta.Y = e.Position.Y;
                ta.Font = new Font("Candara", e.Position.Height / 10, FontStyle.Regular);

                chart1.Annotations.Add(ta);
            }
        }

与此有关的一些问题以及与我发布的其他问题有关的Legend：

My other Pie Chart Legend/ChartArea question

使用此PrePaint设置，我不确定TextAnnotation的位置是否正确。我正在使用e.Position，但它不是“准确地”出现在饼图区域的甜甜圈中间。我希望它能完美居中。不知道在此使用其他什么属性。

第二个问题是，图例文字长度发生变化时，它会“推动”并使ChartArea本身变小，从而使[[饼图变小]。我想反过来，ChartArea 饼图保持相同大小，但Legend被推开。

这可能吗？

以下是饼图的位置设置：

谢谢

Answer 1

首先，我创建了一个字典来存储居中的TextAnnotations引用（关键是图形名称，如果您有多个的话），然后在PrePaint事件中，获取图形中使用的TextAnnotation的正确引用并更新那一个的坐标。

第二，我手动设置InnerPlotPosition，这似乎解决了TextAnnotation居中的问题。当然，您需要像我对这行所做的那样为InnerPlot指定坐标和大小：

chart1.ChartAreas[0].InnerPlotPosition = new ElementPosition(0, 0, 60.65f, 94.99f);

最后，我手动设置图例的位置和大小，并使用扩展方法WrapAt在图例项文本中的每个_maxLegendTextBeforeWrap处设置一个“换行符”。无法找到使其随图例区域的宽度动态变化的方法，因此必须手动设置。

下面是产生的效果的GIF。不知道这是否适合您作为解决方案（根据我的口味，太多的调整和编码），但是无论如何。也许这可以引发一些有关如何解决的新思路。

为此，我创建了这些全局变量：
        /// <summary>
        /// Saves the currently doughnut centered annotations per graph.
        /// </summary>
        private IDictionary<string, TextAnnotation> _annotationsByGraph;
        /// <summary>
        /// Number of characters 
        /// </summary>
        private int _maxLegendTextBeforeWrap = 10;
        /// <summary>
        /// Legend area width.
        /// </summary>
        private int _legendWidth = 20;
        /// <summary>
        /// Legend area height.
        /// </summary>
        private int _legendHeight = 90;

这是Load事件的处理程序：

private void ChartTest_Load(object sender, EventArgs e)
{
    // ** Start of test data **
    chart1.Series["Series1"].Points.AddXY("A", 33);
    chart1.Series["Series1"].Points[0].LegendText = "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
    chart1.Series["Series1"].Points.AddXY("B", 33);
    chart1.Series["Series1"].Points[1].LegendText = "BBBBBBBBBBBBBBBBBBBB";
    chart1.Series["Series1"].Points.AddXY("C", 34);
    chart1.Series["Series1"].Points[2].LegendText = "CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC";
    // ** End of test data **

    // Creates a new instance of the dictionary storing the references to the annotations.
    _annotationsByGraph = new Dictionary<string, TextAnnotation>();
    // Createa a new instance of an annotation for the chart1 graph.
    _annotationsByGraph.Add(chart1.Name, new TextAnnotation());
    // Manually setting the position of the chart area prevents the imperfect positioning of the
    // TextAnnotation at the center of the doughnut.
    chart1.ChartAreas[0].Position.Auto = true;
    // Manually set the position of the InnerPlotPosition area prevents the imperfect positioning of the
    // TextAnnotation at the center of the doughnut.
    chart1.ChartAreas[0].InnerPlotPosition.Auto = false;
    chart1.ChartAreas[0].InnerPlotPosition = new ElementPosition(0, 0, 60.65f, 94.99f);
    // Minimum size for the legend font.
    chart1.Legends[0].AutoFitMinFontSize = 5;
    // Set the legend style as column.
    chart1.Legends[0].LegendStyle = LegendStyle.Column;
    // Splits the legend texts with the space char every _maxLegendTextBeforeWrap characters.
    chart1.Series["Series1"].Points.ToList().ForEach(p => p.LegendText = p.LegendText.WrapAt(_maxLegendTextBeforeWrap));
}

这是PrePaint事件的处理程序：
    private void chart1_PrePaint(object sender, ChartPaintEventArgs e)
    {
        if (e.ChartElement is ChartArea)
        {
            // Get the reference to the corresponding text annotation for this chart.
            // We need this, otherwise we are creating and painting a new instance of a TextAnnotation
            // at every PrePaint, with the resulting blurrying effect caused by the overlapping of the text.
            var ta = _annotationsByGraph[e.Chart.Name];
            // Check if the annotation has already been added to the chart.
            if (!e.Chart.Annotations.Contains(ta))
                e.Chart.Annotations.Add(ta);
            // Set the properties of the centered TextAnnotation.
            ta.IsMultiline = true;
            ta.Text = "Results of Calculation\nx%";
            ta.Font = new Font("Candara", e.Position.Height / 10, FontStyle.Regular);
            ta.Width = e.Position.Width;
            ta.Height = e.Position.Height;
            ta.X = e.Position.X;
            ta.Y = e.Position.Y;
            // Move the legend manually to the right of the doughnut.
            e.Chart.Legends[0].Position = new ElementPosition(e.Position.X + e.Position.Width, e.Position.Y, _legendWidth, _legendHeight);
        }
    }

这是按钮的作用：
        private void BtnChangeLegendItemLength_Click(object sender, EventArgs e)
        {
           if (chart1.Series["Series1"].Points[1].LegendText.StartsWith("DD"))
              chart1.Series["Series1"].Points[1].LegendText = "BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB".WrapAt(_maxLegendTextBeforeWrap);
           else
              chart1.Series["Series1"].Points[1].LegendText = "DDDDDD".WrapAt(_maxLegendTextBeforeWrap);
        }

这是扩展方法定义：
internal static class ExtensionMethods
{
    public static string WrapAt(this string legendText, int maxLengthBeforeWrap)
    {
        if (legendText.Length <= maxLengthBeforeWrap)
            return legendText;
        // Integer division to get how many times we have to insert a space.
        var times = legendText.Length / maxLengthBeforeWrap;
        // Counter of added spaces.
        var spacesAdded = 0;
        // Iterate for each space char needed.
        for (var i = 1; i <= times; i++)
        {
            // Insert a space char every maxLengthBeforeWrap positions.
            legendText = legendText.Insert(maxLengthBeforeWrap * i + spacesAdded, new string(' ', 1));
            spacesAdded++;
        }
        return legendText;
    }
}