How do I scroll a TScrollbar using the mouse wheel?

Question

I have a TScrollBar having a code in the OnScroll event.

I want to scroll it using the mouse wheel, but turning the mouse wheel does not scroll the scroll bar and does not trigger the OnScroll event.

Any idea?

Answer 1

procedure TForm1.FormMouseWheel(Sender: TObject; Shift: TShiftState;
  WheelDelta: Integer; MousePos: TPoint; var Handled: Boolean);
var
  I: Integer;
begin
  Handled := PtInRect(ScrollBox1.ClientRect, ScrollBox1.ScreenToClient(MousePos));
  if Handled then
    for I := 1 to Mouse.WheelScrollLines do
    try
      if WheelDelta > 0 then
        ScrollBox1.Perform(WM_VSCROLL, SB_LINEUP, 0)
      else
        ScrollBox1.Perform(WM_VSCROLL, SB_LINEDOWN, 0);
    finally
      ScrollBox1.Perform(WM_VSCROLL, SB_ENDSCROLL, 0);
    end;
end;

Answer 2

it's too easy just increase the position Value .

procedure TForm1.FormMouseWheel(Sender: TObject; Shift: TShiftState;
WheelDelta: Integer; MousePos: TPoint; var Handled: Boolean);
begin
self.VertScrollBar.Position :=  self.VertScrollBar.Position + WheelDelta;
end;