Winforms pie chart legend text length affects label and chartarea size - winforms

Question

I have the following ChartArea Annotation settings set up:
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);
}
}
A few issues with this, and with the Legend in relation to my other posted question:
My other Pie Chart Legend/ChartArea question
With this PrePaint setup, I'm not sure if my position is correct for the TextAnnotation. I'm using the e.Position but it's coming out not "exactly" centered in the middle of the doughnut of the pie chart area. I'd like it to be centered perfectly. Not sure what other property to use here.
A second issue is that when Legend text length changes, it "pushes" and makes the ChartArea itself smaller so the pie chart gets smaller. I'd like it to be the other way around, where the ChartArea pie chart stays the same size but the Legend gets pushes aside.
Is this possible?
The following is the position setup of the pie chart:
Thanks

Answer 1

I'm sorry I couldn't help more, last time. I tested the centering of the TextAnnotation and in fact it has problems when the InnerPlotPosition is set to auto. Moreover, the answer found at link creates a new instance of the TextAnnotation at every PrePaint, causing the overlapping of TextAnnotations and the blurrying of the centered text.
I couldn't find a way to avoid the resizing of the doughnut (I'm not sure it's even possible, at this point...I'll wait for some other answers) but maybe this can work out as a workaround.
First I created a dictionary to store the centered TextAnnotations references (the key is the graph name, in case you have more than one), then in the PrePaint event I get the correct reference of the TextAnnotation used in the graph and update the coordinates of that one.
Second, I set the InnerPlotPosition manually, this seems to solve the problem of the centering of the TextAnnotation. Of course, you need to specify coordinates and size for the InnerPlot like I did with the line:
chart1.ChartAreas[0].InnerPlotPosition = new ElementPosition(0, 0, 60.65f, 94.99f);
Lastly, I set the position and the size of the legend manually and, with the extension method WrapAt I set a "line break" every _maxLegendTextBeforeWrap in the legend items text. Couldn't find a way to make it dynamically change with the width of the legend area, so it has to be set manually.
Below there's a GIF of the resulting effect. Don't know if this suits you as a solution (too much tweaking and code, for my taste), but anyway. Maybe this can trigger some new ideas on how to solve.
To do so I created these global variables:
/// <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;
This is the handler of the Load event:
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));
}
This is the handler of the PrePaint event:
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);
}
}
This is what the button does:
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);
}
This is the extension method definition:
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;
}
}