System.Windows.Forms.CommandBar.DropDownFilter C# (CSharp) Method

        private bool DropDownFilter(ref Message message)
        {
            if (state != State.HotTracking)
            {
                throw new InvalidOperationException();
            }

            // comctl32 sometimes steals the hot item for unknown reasons.
            this.SetHotItem(this.trackHotItem);

            if (message.Msg == NativeMethods.WM_KEYDOWN)
            {
                Keys keyData = (Keys)(int) message.WParam | ModifierKeys;

                if (keyData == Keys.Left)
                {
                    this.TrackDropDownNext(this.GetPreviousItem(trackHotItem));
                    return true;
                }

                // Only move right if there is no submenu on the current selected item.
                if ((keyData == Keys.Right) && ((this.contextMenu.SelectedMenuItem == null) || (this.contextMenu.SelectedMenuItem.MenuItems.Count == 0)))
                {
                    this.TrackDropDownNext(GetNextItem(trackHotItem));
                    return true;
                }

                if (keyData == Keys.Escape)
                {
                    trackEscapePressed = true;
                }
            }
            else if ((message.Msg == NativeMethods.WM_MOUSEMOVE) || (message.Msg == NativeMethods.WM_LBUTTONDOWN))
            {
                Point point = new Point(((int) message.LParam) & 0xffff, ((int) message.LParam) >> 16);
                point = this.PointToClient(point);

                if (message.Msg == NativeMethods.WM_MOUSEMOVE)
                {
                    if (point != lastMousePosition)
                    {
                        int index = HitTest(point);
                        if ((this.IsValid(index)) && (index != trackHotItem))
                            this.TrackDropDownNext(index);

                        lastMousePosition = point;
                    }
                }
                else if (message.Msg == NativeMethods.WM_LBUTTONDOWN)
                {
                    if (HitTest(point) == trackHotItem)
                    {
                        this.TrackDropDownNext(-1);
                        return true;
                    }
                }
            }

            return false;
        }