Steema Central

Posted: **Sun Feb 20, 2011 5:53 pm**

First - apologies for what is probably a dumb question. So thanks in advance for your help on the forum.
Second - in C++/VCL how do I determine the axis-based coordinates of a mouse click in a chart? That's to say, not the cursor coordinates on the Chart object itself (which start at 0,0 top-left) but within the displayed graph (with currently visible axes ranges)?

Posted: **Tue Feb 22, 2011 2:27 pm**

Hi philip,

You can translate the coordinates in pixels taken, for example, from OnMouseDown event to coordinates in the axes units with CalcPosPoint function:

Code: Select all

procedure TForm1.Chart1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
var XPos, YPos: Double;
begin
  XPos:=Chart1.Axes.Bottom.CalcPosPoint(X);
  YPos:=Chart1.Axes.Left.CalcPosPoint(Y);
  Chart1.Title.Text.Text:='X: ' + FormatFloat('#0.00', XPos) + ', Y: ' + FormatFloat('#0.00', YPos);
end;

Posted: **Tue Feb 22, 2011 4:07 pm**

Code: Select all

  XPos:=Chart1.Axes.Bottom.CalcPosPoint(X);
  YPos:=Chart1.Axes.Left.CalcPosPoint(Y);

perfect. many thanks

Posted: **Tue Feb 22, 2011 5:10 pm**

You're welcome, Philip!

Steema Central

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