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ListBox Scroll

Posted on 1998-06-27
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Last Modified: 2010-04-04
Besides its automatic behaviour, what command should I use to scroll content of ListBox during run-time, whenever I want? (horizontaly, verticaly)
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Question by:bor061297
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by:mikepj
ID: 1356027
ListBox.TopIndex:=whatever
I don't know how to do the horizontal scrolling of a listbox but there must be a way.  Besides, I don't know why you would want to be able to do that programmatically.
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by:kjteng
ID: 1356028
You mean u want both hori/vert scrollbars to appear as and when you need it?

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by:bor061297
ID: 1356029
>>I don't know how to do the horizontal scrolling of a listbox
>> but there must be a way.  Besides, I don't know why you would >>want to be
>>able to do that programmatically.

I want to make a ListBox that allows user to scrool it left/right with CTRL+ LEFT/RIGHT CRSR
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by:kjteng
ID: 1356030
I think I know how to do that.
please reject the current answer so that I can post mine
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by:kjteng
ID: 1356031
I think I know how to do that.
please reject the current answer so that I can post mine
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Expert Comment

by:Edo082297
ID: 1356032
Delphi's TListBox component automatically implements a vertical scrollbar. The scrollbar appears when the list box isn't tall enough to display all its items. However, the list box doesn't display a horizontal scrollbar when its items are wider than its width. Of course, there's a way for you to add the horizontal scrollbar.

Add the following code to the OnCreate event of your form:

procedure TForm1.FormCreate(Sender: TObject);
var
  i, MaxWidth: integer;
begin
  MaxWidth := 0;
  for i := 0 to ListBox1.Items.Count - 1 do
    if MaxWidth < ListBox1.Canvas.TextWidth (ListBox1.Items.Strings[i]) then
      MaxWidth := ListBox1.Canvas.TextWidth(ListBox1.Items.Strings[i]);
  SendMessage(ListBox1.Handle, LB_SETHORIZONTALEXTENT, MaxWidth+2, 0);
end;

The code finds the width, in pixels, of the longest string in the list box. Then, it uses the LB_SETHORIZONTALEXTENT message to set the horizontal scrollable width, in pixels, of the list box. The two extra pixels added to MaxWidth help offset narrow characters from the right edge of the list box.

If you want to set a scroll bar to a particular line:

  SelStart := Perform( EM_LINEINDEX, LineNumber, 0 );
  Perform( EM_SCROLLCARET, 0, 0 );

If you look up the EM_ functions you'll find everything you need for concise control of your listbox scrollbars.

HTH

Edo

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by:kjteng
ID: 1356033
use the sendMessage as follows (w is the width to scroll in pixels):
sendMessage( listbox1.handle, lb_sethorizontalExtent, w ,0)

My answer is similar to that of Edo. Since he has posted the comment, he should get the points.


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Expert Comment

by:Edo082297
ID: 1356034
Thanks, kjetng.

Bor, if you want some help key trapping the ctrl-left and right, just let us know, it is fairly straight forward.

Edo
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by:bor061297
ID: 1356035
How to post points to EDO?
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Accepted Solution

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Edo082297 earned 100 total points
ID: 1356036
Hi Bor,

   I hope this is OK! If you want more info, just let me know :)

Thanks
Edo
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