Question

“How can I calculate the x,y position of the chart when clicked in the viewer?”

Solution

The can be accomplished by implementing the Chart.OnDrawCommandClick event to convert the mouse position to chart coordinate space.

Download: CalcChartPosClicked.zip

procedure TForm1.ehTeeChart_DrawCommandClick(Sender, aDrawCommand: TObject);
var
  lViewer: TppViewer;
  lCursorPos: TPoint;
  lDrawCommandPos: TPoint;
  lChartPos: TPoint;
begin

  // get reference to report viewer
  lViewer := TppViewer(ppReport1.PreviewForm.Viewer);

  // get mouse pos
  GetCursorPos(lCursorPos);

  // convert to viewer coords
  lCursorPos := lViewer.PaintBox.ScreenToClient(lCursorPos);

  // get pos of the chart image
  lDrawCommandPos := TppDrawCommand(aDrawCommand).DrawRect.TopLeft;

  // get chart pos clicked
  lChartPos.X := lCursorPos.X -  lDrawCommandPos.X;
  lChartPos.Y := lCursorPos.Y -  lDrawCommandPos.Y;

  // adjust for viewer scaling (i.e. viewer support zoom)
  lChartPos.X := Round(lChartPos.X / lViewer.ScreenDevice.ScaleX);
  lChartPos.Y := Round(lChartPos.Y / lViewer.ScreenDevice.ScaleY);

  ShowMessage('Chart clicked: ' + IntToStr(lChartPos.X) + ',' + IntToStr(lChartPos.Y));

end;