EasyMap VCL
TEasyMap.ScreenToMap
procedure ScreenToMap(sX: Integer; sY: Integer; var mX: Extended; var mY: Extended);
Description
Converts screen coordinates to map coordinates with the account of current zoom ratio and map central point.

procedure TForm1.MapMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
var
 sym: TSymbol;
begin
 Map.ScreenToMap(X, Y, mX, mY);
 sym.X := mX;
 sym.Y := mY;
 Map.Layers.Last.AddObject(sym);
end;