procedure TTree.AuxCalc(ANode: PNode);
begin
  if ANode = FRoot then begin
    ANode^.FY := 0;
  end;
  if ANode^.FLeft <> nil then begin
    ANode^.FLeft^.FY := ANode^.FY + VSpace + 2 * NodeSize;
    AuxCalc(ANode^.FLeft);
  end;
  if ANode^.FRight <> nil then begin
    ANode^.FRight^.FY := ANode^.FY + VSpace + 2 * NodeSize;
    AuxCalc(ANode^.FRight);
  end;
  if (ANode^.FLeft = nil) and (ANode^.FRight = nil) then begin
    ANode^.FHeight := 2 * NodeSize;
    ANode^.FWidth := 2 * NodeSize;
  end
  else begin
    if (ANode^.FLeft <> nil) and (ANode^.FRight = nil) then begin
      ANode^.FHeight := ANode^.FLeft^.FHeight + VSpace + 2 * NodeSize;
      ANode^.FWidth := ANode^.FLeft^.FWidth + HSpace;
    end
    else begin
      if (ANode^.FLeft = nil) and (ANode^.FRight <> nil) then begin
        ANode^.FHeight := ANode^.FRight^.FHeight + VSpace + 2 * NodeSize;
        ANode^.FWidth := ANode^.FRight^.FWidth + HSpace;
      end
      else begin
        ANode^.FHeight := Max(ANode^.FLeft^.FHeight, ANode^.FRight^.FHeight) +
                              VSpace + 2 * NodeSize;
        ANode^.FWidth := ANode^.FLeft^.FWidth + ANode^.FRight^.FWidth + HSpace;
      end;
    end;
    case FRootPositionStyle of
      0: begin
        ANode^.FX := ANode^.FWidth div 2;
      end;
      1: begin
      end
      else begin
      end;
    end;
  end;
end;




















procedure TTree.DrawTree(ANode: PNode; AX, AY: Integer; ACanvas: TCanvas);
  { pre: AX, AY are absolute coordinates of upper left-hand corner of
         the bounding box;
         ANode points to a binary search tree with up-to-date layout info
    post: ANode has been drawn on the canvas according to its layout info }
var
  HRect: TRect;
begin
  if ANode^.FLeft <> nil then begin
    ACanvas.MoveTo(ANode^.FX + NodeSize, ANode^.FY + NodeSize);
    ACanvas.LineTo(ANode^.FLeft^.FX + NodeSize, ANode^.FLeft^.FY);
    DrawTree(ANode^.FLeft, 0, 0, ACanvas);
  end;
  if ANode^.FRight <> nil then begin
    ACanvas.MoveTo(ANode^.FX + NodeSize, ANode^.FY + NodeSize);
    ACanvas.LineTo(ANode^.FRight^.FX + NodeSize, ANode^.FRight^.FY);
    DrawTree(ANode^.FRight, 0, 0, ACanvas);
  end;
  if FDrawEmptyTrees = True then begin
  end;
  if FDrawBoundingBoxes = True then begin
    if ANode^.FWidth <> 2 * NodeSize then begin
      ACanvas.Brush.Color := clWhite;
      ACanvas.Pen.Color := clBlack;
      HRect.Left := 0;
      HRect.Right := ANode^.FWidth - 1;
      HRect.Top := ANode^.FY;
      HRect.Bottom := ANode^.FY + ANode^.FHeight;
      ACanvas.MoveTo(HRect.Left, HRect.Top);
      ACanvas.LineTo(HRect.Right, HRect.Top);
      ACanvas.LineTo(HRect.Right, HRect.Bottom);
      ACanvas.LineTo(HRect.Left, HRect.Bottom);
      ACanvas.LineTo(HRect.Left, HRect.Top);
    end;
  end;
  ACanvas.Pen.Color := clBlack;
  ACanvas.Brush.Color := clYellow;
  HRect.Left := ANode^.FX + 1;
  HRect.Right := ANode^.FX + 2 * NodeSize - 1;
  HRect.Top := ANode^.FY + 1;
  HRect.Bottom := ANode^.FY + 2 * NodeSize - 1;
  ACanvas.Rectangle(HRect.Left - 1, HRect.Top - 1, HRect.Right + 1, HRect.Bottom + 1);
  ACanvas.TextRect(HRect, ANode^.FX + 1, ANode^.FY + 1, IntToStr(ANode^.FValue));
end;