delphi - How can I omit the grid lines of empty cells in a list view?

Question

How can I hide the grid lines separating empty cells from the adjacent cells in a TListView control? It would be like the HTML colspan table attribute, or Excel's "merge cells" command. I would like for cells with text in them to retain their normal borders.

Answer 1

You could use TVirtualStringTree. It has option toAutoSpanColumns which will automatically span empty columns.

Answer 2

There seems not to exist any robust solution to this problem.

A bad solution, however, is

procedure TForm4.FormShow(Sender: TObject);
var
  i: integer;
begin
  ListView1.ViewStyle := vsReport;
  ListView1.Columns.Add.Caption := 'Col 1';
  ListView1.Columns.Add.Caption := 'Col 2';
  ListView1.Columns.Add.Caption := 'Col 3';
  ListView1.GridLines := false; // You cannot have grid lines...
  for i := 0 to 10 do
    with ListView1.Items.Add do
    begin
      if i <> 5 then
      begin
        Caption := 'Test';
        SubItems.Add('test');
        SubItems.Add('test');
      end
      else
        Caption := 'This is a very, very long caption';
    end;
end;

var
  ColWidths: array of integer;

procedure TForm4.ListView1AdvancedCustomDraw(Sender: TCustomListView;
  const ARect: TRect; Stage: TCustomDrawStage; var DefaultDraw: Boolean);
var
  i, j: Integer;
begin
  if Stage <> cdPrePaint then Exit;
  if length(ColWidths) <> TListView(Sender).Columns.Count then
  begin
    SetLength(ColWidths, TListView(Sender).Columns.Count);
    Exit;
  end;
  for i := 0 to length(ColWidths) - 1 do
    if ColWidths[i] <> Sender.Column[i].Width then
    begin
      Sender.Invalidate;
      for j := 0 to length(ColWidths) - 1 do
        ColWidths[i] := Sender.Column[i].Width;
    end;
end;

procedure TForm4.ListView1AdvancedCustomDrawItem(Sender: TCustomListView;
  Item: TListItem; State: TCustomDrawState; Stage: TCustomDrawStage;
  var DefaultDraw: Boolean);
var
  r: TRect;
begin
  DefaultDraw := (Item.SubItems.Count <> 0);
  if not DefaultDraw then
  begin
    FillRect(Sender.Canvas.Handle, Item.DisplayRect(drBounds), GetStockObject(WHITE_BRUSH));
    r := Item.DisplayRect(drBounds);
    DrawText(Sender.Canvas.Handle, Item.Caption, length(Item.Caption), r, DT_SINGLELINE or DT_LEFT or DT_VCENTER)
  end;
end;

This is bad because it is not robust. It flickers, it's buggy, and it is "hacky". It might not work well in future versions of Windows. Basically, the Windows list view control isn't supposed to do HTML-like colspan, I think.