Author: Maarten de Haan

How to scroll a TTreeView?

Answer:
1   
2   procedure TForm1.FormMouseWheelUp(Sender: TObject;
3     Shift: TShiftState;
4     MousePos: TPoint;
5     var Handled: Boolean);
6   
7   var
8     iPos: Integer;
9   
10  begin
11    iPos := GetScrollPos(Form1.TreeView1.Handle, SB_VERT);
12    SetScrollPos(Form1.TreeView1.Handle, SB_VERT, iPos - 1, True);
13    // Don't set Handled to True otherwise the scrollbar scrolls
14    // but the content of the TreeView does NOT scroll!
15    // I have not found a way to check if the TreeView has a scrollbar or not.
16    // Maybe if you first call:
17    // GetScrollRange(Form1.TreeView1.Handle, SB_VERT,lpMinPos,lpMaxPos);
18    // and then:
19    // if MaxPos = 0 and MinPos = 0 then there is no vertical scrollbar
20    // if MaxPos <> 0 then there is a vertical scrollbar
21  end;