How to remove the dotted focus rectangle from TListBox?

I am using ListBox.Style := lbOwnerDrawFixed with OnDrawItem:

procedure TForm1.ListBox1DrawItem(Control: TWinControl; Index: Integer;
  ARect: TRect; State: TOwnerDrawState);
begin
  with ListBox1.Canvas do begin
    Brush.Color := clWhite;
    Pen.Color := clWhite;
    FillRect(ARect);
  end;
end;

It should give an empty space to draw anything I want, but it doesn't. When the item is focued I still can see a dotted rectangle around it.

How to remove the rectangle?

The focus rectangle is drawn by the VCL ^(*) in TCustomListBox.CNDrawItem after the OnDrawItem event handler returns.

procedure TCustomListBox.CNDrawItem(var Message: TWMDrawItem); 

...

  ..
    if Integer(itemID) >= 0 then
      DrawItem(itemID, rcItem, State)      //-> calls message handler
    else
      FCanvas.FillRect(rcItem);
    if (odFocused in State) and not TStyleManager.IsCustomStyleActive then
      DrawFocusRect(hDC, rcItem);          //-> draws focus rectangle
  ..
..

Whatever you draw in the event handler will later get focused by the VCL.

But notice that VCL use DrawFocusRect to draw the focus rectangle:

Because DrawFocusRect is an XOR function, calling it a second time with the same rectangle removes the rectangle from the screen.

So just call DrawFocusRect yourself and let VCL's call erase it:

procedure TForm1.ListBox1DrawItem(Control: TWinControl; Index: Integer;
  ARect: TRect; State: TOwnerDrawState);
begin
  with ListBox1.Canvas do begin
    Brush.Color := clWhite;
    Pen.Color := clWhite;
    FillRect(ARect);
    if odFocused in State then  // also check for styles if there's a possibility of using ..
      DrawFocusRect(ARect);
  end;
end;

---

^{(*) Normally default window procedure draws the focus rectangle for an owner drawn list box item in response to a WM_DRAWITEM message. But the default window procedure is not called for a list box in VCL's handling of the message.}