procedure TForm1.FormCreate(Sender: TObject);
begin
  TMSFMXDirectoryTreeView1.NodesAppearance.FixedHeight := 40;
  TMSFMXDirectoryTreeView1.AddColumn(tvckFreeSpaceAndTotalSize);
  TMSFMXDirectoryTreeView1.Columns[1].VerticalTextAlign := tvtaLeading;
  TMSFMXDirectoryTreeView1.LoadDrives;
end;

procedure TForm1.TMSFMXDirectoryTreeView1AfterDrawNodeText(Sender: TObject;
  ACanvas: TCanvas; ARect: TRectF; AColumn: Integer;
  ANode: TTMSFMXTreeViewVirtualNode; AText: string);
var
  r, rs: TRectF;
  fs, fst: Int64;
  s: String;
begin
  if AColumn = 1 then
  begin
    s := TTMSFMXDirectoryTreeViewNode(ANode.Node).FileName;
    if ExtractFileDrive(s) + PathDelim = s then
    begin
      fst := DiskSize(Ord(UpperCase(s)[1]) - 64);
      fs := DiskFree(Ord(UpperCase(s)[1]) - 64);
      if (fst > -1) and (fs > -1) then
      begin
        r := ARect;
        r.Top := r.Bottom - 20;
        r.Height := 20;
        InflateRect(r, 0, -2);
        r.Width := r.Width - 2;
        r := RectF(Int(r.Left) + 0.5, Int(r.Top) + 0.5, Int(r.Right) - 0.5, Int(r.Bottom) - 0.5);
        rs := r;
        rs.Width := rs.Width * fs / fst;
        ACanvas.Fill.Kind := TBrushKind.Solid;
        ACanvas.Fill.Color := claWhite;
        ACanvas.FillRect(r, 0, 0, AllCorners, 1);
        ACanvas.Fill.Color := claSteelblue;
        ACanvas.FillRect(rs, 0, 0, AllCorners, 1);
        if TMSFMXDirectoryTreeView1.IsNodeSelected(ANode.Node) then
          ACanvas.Stroke.Color := claWhite
        else
          ACanvas.Stroke.Color := claDarkgray;

        ACanvas.DrawRect(r, 0, 0, AllCorners, 1);
      end;
    end;
  end;
end;