Add value on mouse pos

[CT]

When I click on the chart I want to add a value on this position. How can I calculate the chart x/y position from the mouse position?

[Narcís]

Hi CT,

You can do that using TChart's OnMouseDown event:

Code: Select all

procedure TForm1.Chart1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
var xval, yval: Double;
begin
  xval:=Series1.XScreenToValue(X);
  yval:=Series1.YScreenToValue(Y);

  Series1.AddXY(xval,yval);
end;

[CT]

Hm, xval and yval are always 0. I try it out with a fresh chart, having one series.

[Narcís]

Hi CT,

This is because to get it working you need to already have some values on the series as done here:

Code: Select all

procedure TForm1.FormCreate(Sender: TObject);
begin
  Series1.FillSampleValues(2);
end;

procedure TForm1.Chart1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
var xval, yval: Double;
begin
  xval:=Series1.XScreenToValue(X);
  yval:=Series1.YScreenToValue(Y);

  Series1.AddXY(xval,yval);
end;

Other alternatives would be using a TDrawLineTool or custom drawing on TChart's canvas.

For more information on TChart tools please have a look at the features demo at the TeeChart program group. For information on how to custom draw on the canvas, have a look at the tutorials at the TeeChart "Docs" folder and on the features demo as well.

[CT]

Even I have some values added it does not work. All values are added on 0, 0 but if I scroll the chart a little bit it workes. For my needs that is OK.

[Narcís]

Hi CT,

It's ok for us if it's ok for your needs. However if you want us to look further at it please send us an example we can run "as-is" to reproduce the problem here spceifying wich TeeChart version you are using.

You can post your files at [url]news://www.steema.net/steema.public.attachments[/url] newsgroup.