Steema Central

Posted: **Fri Sep 02, 2022 8:16 am**

Hello. I've tried to use GetPointerStyle event to apply different styles to line segments as described here:

private void Form1_Load(object sender, EventArgs e)
{
	var lineChart = new Line();
	lineChart.LinePen.Width = 2;
	lineChart.Pointer.Style = PointerStyles.Circle;
	lineChart.Pointer.Visible = true;

	tChart1.Series.Add(lineChart);

	lineChart.FillSampleValues(10);
	lineChart.GetPointerStyle += line_GetPointerStyle;
}


void line_GetPointerStyle(Steema.TeeChart.Styles.CustomPoint series, Steema.TeeChart.Styles.GetPointerStyleEventArgs e)
{
	if ((e.ValueIndex == 3) || (e.ValueIndex == 6))
		series.LinePen.Style = Steema.TeeChart.Drawing.DashStyle.Dash;
	else
		series.LinePen.Style = Steema.TeeChart.Drawing.DashStyle.Solid;
}

As you can see I want a segment that leads to point #3 and a segment that leads to point #6 to be dashed.
But as the result a segment that leads to point #5 and a segment that leads to point #8 is dashed:

: Безымянный.png (30.76 KiB) Viewed 2845 times

I use Steema.TeeChart.NET 4.2022.05.26 on .NET 5.0 (that also reproduces with latest Steema.TeeChart.NET 4.2022.08.23).
Looks like a bug or am I missing something?

Posted: **Fri Sep 02, 2022 10:27 am**

Hello,

bairog wrote: ↑
Fri Sep 02, 2022 8:16 am
Looks like a bug or am I missing something?

In this particular case, I think the GetPointerStyle is not the best event to use—if you use the BeforeDrawPoint event you will obtain the results you expect:

Code: Select all

    private void InitializeChart()
    {
      var lineChart = new Line();
      lineChart.LinePen.Width = 2;
      lineChart.Pointer.Style = PointerStyles.Circle;
      lineChart.Pointer.Visible = true;

      tChart1.Series.Add(lineChart);

      lineChart.FillSampleValues(10);
      //lineChart.GetPointerStyle += line_GetPointerStyle;
      lineChart.BeforeDrawPoint += LineChart_BeforeDrawPoint;

      tChart1.Legend.Visible = false;
    }

    private void LineChart_BeforeDrawPoint(Series Series, BeforeDrawPointEventArgs e)
    {
      var series = (CustomPoint)Series;
      if ((e.ValueIndex == 3) || (e.ValueIndex == 6))
        series.LinePen.Style = Steema.TeeChart.Drawing.DashStyle.Dash;
      else
        series.LinePen.Style = Steema.TeeChart.Drawing.DashStyle.Solid;
    }

: Screenshot from 2022-09-02 12-25-28.png (34.58 KiB) Viewed 2836 times

This is because the GetPointerStyle is specific to the pointer, and in the source-code is called after the line is drawn.

Posted: **Fri Sep 02, 2022 10:33 am**

Thank you, BeforeDrawPoint event is working correctly. But but I'm still curious why GetPointerStyle event woks unexpected way?

Posted: **Fri Sep 02, 2022 10:47 am**

bairog wrote: ↑
Fri Sep 02, 2022 10:33 am
Thank you, BeforeDrawPoint event is working correctly. But but I'm still curious why GetPointerStyle event woks unexpected way?

In essence, what's happening is this (pseudo code)

Code: Select all

foreach (var point in series)
{
     void DrawPoint(Point point)
     {
          void DrawPointer(Point point)
          {
               DoDrawPointerEvent(point);
               /*draw the pointer*/
          }

          DoDrawPointEvent(point);
          DrawLine(point);
          DrawPointer(point);
     }
    
     DrawPoint(point);
}

So by the time we draw the pointer the line has already been drawn, meaning that changes to the ChartPen of the line won't be drawn until the next cycle.

Steema Central

Using GetPointerStyle event to apply different styles to line segments works incorrectly

Using GetPointerStyle event to apply different styles to line segments works incorrectly

Re: Using GetPointerStyle event to apply different styles to line segments works incorrectly

Re: Using GetPointerStyle event to apply different styles to line segments works incorrectly

Re: Using GetPointerStyle event to apply different styles to line segments works incorrectly