Author: Tomas Rutkauskas

I have a listbox on a form which contains a list of stuff of varying widths. In 
some situations, they all fit in the box, in some cases the entries are too long to 
fit and their right end gets cropped. Is there some way to force the listbox to set 
a horizontol scrollbar if and only if an entry is being cropped? I can brute force 
set the ScrollWidth property to 1000, but this puts a scrollbar in place all the 
time. I only want a scrollbar if it's necessary.

Answer:

1   { ... }
2   listbox.Scrollwidth := CalcMaxWidthOfStrings(listbox.Items, listbox.font);
3   { ... }
4   
5   function CalcMaxWidthOfStrings(aList: TStrings; aFont: TFont): Integer;
6   var
7     max, n, i: Integer;
8     canvas: TCanvas;
9   begin
10    Assert(Assigned(aList));
11    Assert(Assigned(aFont));
12    canvas := TCanvas.Create;
13    try
14      canvas.Handle := CreateDC('DISPLAY', nil, nil, nil);
15      try
16        Canvas.Font := aFont;
17        max := 0;
18        for i := 0 to aList.Count - 1 do
19        begin
20          n := Canvas.TextWidth(aList[i]);
21          if n > max then
22            max := n;
23        end;
24        Result := max;
25      finally
26        DeleteDC(canvas.Handle);
27        canvas.Handle := 0;
28      end;
29    finally
30      canvas.free;
31    end;
32  end;