Delphi + TeeChart : how can I get checkbox in legend for pie serie values?

Question

I want to allow the user to choose what values are shown in a chart with a pie serie values by displaying a check box in front of each serie's value.

There is an option to display a checkbox near each legend item but it's only working for series, not values in a serie ; and you can only have one serie of values in a single pie.

Does anyone have any idea on how to achieve this?

This is not possible with the current TeeChart legend. How would you expect the pie to look when you unselect a value in the legend? — Yeray
The expected behaviour would be the same for values as it is for series with bar chart or stacked bar chart : the pie would display all checked values as if the unchecked values were not part of the serie (in bar chart or stacked bar chart, unchecking a serie removes it from the chart but not from the legend) — Jean-Louis Senegas

Yeray Yeray · Accepted Answer · 2017-05-11T13:00:43

You could draw your custom legend manually. However, you should do some tricks:

use a dummy series to store the original values and show these values in the legend.
remove the values from the main series that have been clicked in the legend taking care with the indexes and the colors.

Here an example, even with mouse Hover:

uses Series, TeCanvas, Math;

var pieSeries: TPieSeries;
    dummySeries: TPieSeries;
    itemRect: array of TRect;
    itemIndex: Integer;

procedure TForm1.Chart1AfterDraw(Sender: TObject);
var i, tmpH, tmpW: Integer;
    tmpR, tmpS: TRect;
begin
  with Chart1.Canvas do
  begin
    AssignFont(Chart1.Legend.Font);
    AssignBrush(Chart1.Legend.Brush);

    tmpW:=0;
    tmpH:=0;
    for i:=0 to dummySeries.Count-1 do
    begin
      tmpW:=Max(TextWidth(dummySeries.LegendString(i, Chart1.Legend.TextStyle)), tmpW);
      tmpH:=Max(TextHeight(dummySeries.LegendString(i, Chart1.Legend.TextStyle)), tmpH);
    end;

    Inc(tmpW, Chart1.Legend.Symbol.Width + TeeCheckBoxSize + 8);

    tmpR.Left:=Chart1.Width-tmpW-10;
    tmpR.Top:=50;
    tmpR.Right:=tmpR.Left+tmpW;
    tmpR.Bottom:=tmpR.Top + ((tmpH+4) * dummySeries.Count) + 4;

    Rectangle(tmpR);

    Inc(tmpR.Left, 4);
    tmpS.Left:=tmpR.Left+TeeCheckBoxSize+4;
    tmpS.Right:=tmpS.Left+TeeCheckBoxSize;
    for i:=0 to dummySeries.Count-1 do
    begin
      Brush.Color:=OperaPalette[i];
      Inc(tmpR.Top, 4);

      DrawCheckBox(tmpR.Left, tmpR.Top, not dummySeries.IsNull(i), clNone);

      if i=itemIndex then
      begin
        Pen.Color:=clRed;
        Font.Color:=clRed;
      end
      else
      begin
        Pen.Color:=Chart1.Legend.Symbol.Pen.Color;
        Font.Color:=Chart1.Legend.Font.Color;
      end;

      tmpS.Top:=tmpR.Top+1;
      tmpS.Bottom:=tmpS.Top+TeeCheckBoxSize;
      Rectangle(tmpS);

      TextOut(tmpS.Right + 2, tmpR.Top, StringReplace(dummySeries.LegendString(i, Chart1.Legend.TextStyle), TeeColumnSeparator, ' ', [rfReplaceAll, rfIgnoreCase]));

      itemRect[i]:=Rect(tmpR.Left, tmpS.Top, tmpR.Right, tmpS.Bottom);

      Inc(tmpR.Top, tmpH);
    end;
  end;
end;

procedure TForm1.Chart1Click(Sender: TObject);
var i, j: Integer;
begin
  if itemIndex>-1 then
  begin
     dummySeries.SetNull(itemIndex, not dummySeries.IsNull(itemIndex));

     pieSeries.CheckDataSource;

     for i:=pieSeries.Count-1 downto 0 do
       if pieSeries.IsNull(i) then
          pieSeries.Delete(i);

     //Fix colors
     j:=0;
     for i:=0 to dummySeries.Count-1 do
       if not dummySeries.IsNull(i) then
       begin
         pieSeries.ValueColor[j]:=OperaPalette[i];
         Inc(j);
       end;
  end;
end;

procedure TForm1.Chart1MouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
var i, j: Integer;
begin
  itemIndex:=-1;
  for i:=0 to length(itemRect)-1 do
    if PointInRect(itemRect[i], X, Y) then
    begin
      itemIndex:=i;
      break;
    end;

  if itemIndex>-1 then
  begin
    if dummySeries.IsNull(itemIndex) then
       pieSeries.Selected.HoverIndex:=-1
    else
    begin
      j:=0;
      for i:=0 to itemIndex-1 do
        if not dummySeries.IsNull(i) then
          Inc(j);

      pieSeries.Selected.HoverIndex:=j;
    end;
  end;

  Chart1.CancelMouse:=True;
  Chart1.Repaint;
end;

procedure TForm1.FormCreate(Sender: TObject);
var i: Integer;
begin
  pieSeries:=Chart1.AddSeries(TPieSeries) as TPieSeries;
  pieSeries.FillSampleValues;

  for i:=0 to pieSeries.Count-1 do
    pieSeries.ValueColor[i]:=OperaPalette[i];

  dummySeries:=CloneChartSeries(pieSeries) as TPieSeries;
  dummySeries.ParentChart:=nil;

  pieSeries.DataSource:=dummySeries;

  Chart1.Legend.Visible:=False;
  Chart1.MarginRight:=20;

  SetLength(itemRect, dummySeries.Count);

  itemIndex:=-1;
end;

Delphi + TeeChart : how can I get checkbox in legend for pie serie values?

1 Answers