changing the color of some of the labels

[Nati]

hi

the bottom axis contains dates. for each date i want to check if it answers a certain condition
if so, it should be blue, otherwise black.

i did the following just to check:

procedure Tfrm.Chart1GetAxisLabel(Sender: TChartAxis;
Series: TChartSeries; ValueIndex: Integer; var LabelText: String);
begin
inherited;
if not Sender.IsDateTime then exit;
if valueindex mod 2 = 0 then
sender.LabelsFont.Color := clblue
else
sender.LabelsFont.Color := clblack;
end;

but the event is not even triggered
how can i accomplish what i wrote above?
thanks

[Sandra]

Hello Nati,

If you want change color of labels font alternately, you can not use LabelFont so it property change color of all labels. I recommend use custom labels as do in next example:

Code: Select all

procedure TForm1.FormCreate(Sender: TObject);
var i: Integer;
    dt: TDateTime;
    myColor: TColor;
begin
  Chart1.AddSeries(TLineSeries.Create(Self));

  for i:=0 to 10 do
  begin
    dt:=Now + i;
    Chart1[0].AddXY(dt, random, DateToStr(dt));
  end;

  Chart1.Axes.Bottom.Items.Clear;

  for i:=0 to Chart1[0].Count-1 do
  begin
    if i mod 2 <> 0 then
      myColor:=clRed
    else
      myColor:=clBlack;

    Chart1.Axes.Bottom.Items.Add(Chart1[0].XValue[i], Chart1[0].Labels[i]).Format.Font.Color:=myColor;
  end;

  Chart1.Axes.Bottom.LabelsAngle:=90;
end;

Could you please, tell us if previous code works as you want?

I hope will helps.

Thanks,

[Nati]

hi

this is not exactly what i need.
the data is coming from a cds so at first i fill the data inside the cds and the graph is updated accordingly.
for each date value (x/bottom axis) i need to check if it answers a certain criteria and paint it accordingly.

thanks

[Sandra]

Hello Nati,

Could you please, try to arrange a simple example project we can run as-is to reproduce the problem here?

Thanks,

[Nati]

actually there is no problem just a question

im using TDBChart which values are coming from a cds
and the question is: how can i control the color of each label in the bottom axis

[Sandra]

Hello Nati,

I 'm afraid that the only way you have for controlling labels colors is using custom labels as I do in the example above.

Thanks,

[Nati]

hi

thanks, it actually seems to do the trick

[Sandra]

Hello Nati,

I am glad that now solution works for you .

Thanks,

[Yeray]

Hi,

However, I think that the OnGetAxisLabel event should allow you to change the labels font, and it did in v8.07.
I've added it to the defect list be investigated for future releases (TV52015315).

[Yeray]

Hello,

Investigating this, it claimed to us that it is already possible with events too. You only have to use the axis OnDrawLabel event instead of the chart's OnGetAxisLabel.
Here it is an example of the usage:

Code: Select all

  private
    { Private declarations }
    procedure OnBottomAxisDawLabel(Sender:TChartAxis; var X,Y,Z:Integer; var Text:String; var DrawLabel:Boolean);
//...
uses Series;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Chart1.AddSeries(TLineSeries);
  Chart1[0].FillSampleValues(10);

  Chart1.Axes.Bottom.OnDrawLabel:=OnBottomAxisDawLabel;
end;

procedure TForm1.OnBottomAxisDawLabel(Sender:TChartAxis; var X,Y,Z:Integer; var Text:String; var DrawLabel:Boolean);
begin
  If Round(StrToFloat(Text)) mod 2 = 0 Then
    Chart1.Canvas.Font.Color:=clRed
  else
    Chart1.Canvas.Font.Color:=clGreen;
end;

So we've closed the ticket with number [TV52015315].

[TestAlways]

Is there any way to get the X index from the X variable (which appears to be the pixels)? The text assigned to the "Text" variable can vary.

Thank you,

Ed Dressel

[Yeray]

Hi Ed,

I'm afraid you have to loop into your series values looking for an ValueIndex that matches with the x pixel you have

[TestAlways]

I tried the following LOC but X never equals lSrs.CalcXPos(I) (FRedLblIndexes is a TList of integer and contain the index of values that should be drawn in red):

Code: Select all

procedure TfrmDBCalcRetirementYears.ChartBottomAxisDrawLabel(Sender:TChartAxis; var X,Y,Z:Integer; var Text:String; var DrawLabel:Boolean);
var
  I: Integer;
  lChart: TChart;
  lIdx: Integer;
  lSrs: TChartSeries;
begin
  Assert(Sender.ParentChart is TChart);
  lChart := TChart(Sender.ParentChart);
  if lChart.SeriesCount > 0 then
  begin
    lSrs := lChart.Series[0];
    lIdx := -1;
    for I := 0 to  lSrs.Count - 1 do
      if lSrs.CalcXPos(I) = X then
      begin
        lIdx := I;
        break;
      end;
    if (lIdx > -1) and (FRedLblIndexes.IndexOf(X) > -1) then
      lChart.Canvas.Font.Color := clRed;
  end;
end;

What should I do differently?

Ed Dressel

[TestAlways]

Attached is a demo that reproduces the problem. It appears that with a bar series, CalcXPos gives the left side of the bar and the X parameter is the center of the bar. (In the attached demo, the caption shows the X, Y position of the mouse when it is over the TChart, along with the CalcXPos and X values for Series[0]).

I am pressed to get this working.

Ed Dressel

[Narcís]

Hi Ed,

You can calculate bar's center position from CalcBarBounds method implementing ChartBottomAxisDrawLabel as shown below. You'll see values in both lists coinciding now.

Code: Select all

procedure TForm1.ChartBottomAxisDrawLabel(Sender: TChartAxis; var X, Y,
  Z: Integer; var Text: String; var DrawLabel: Boolean);
var
  I     : Integer;
  lValue: Integer;
  rect  : TRect;
  XPos  : Integer;
begin
  lValue := StrToIntDef(Text, -1);
  if lValue < 0 then
  begin
    lbxXValues.Items.Clear;
    lbxCalcXPos.Items.Clear;
    for I := Series1.Count - 1 downto 0 do
    begin
      rect := Series1.CalcBarBounds(I);
      XPos := rect.Left + ((rect.Right - rect.Left) div 2);
      lbxCalcXPos.Items.Add(Format('X Pos for %d: %d', [I, XPos]));
    end;
  end
  else
    lbxXValues.Items.Add(Text + ': ' + IntToStr(X));
end;