EnsureVisible for ListViewSubItem

• Download source - 957 B

Introduction 

It extends the ListView control and adds an EnsureVisible method to scroll horizontally to a subitem.

Background   

I often use The Code Project to find good samples, but I didn't find one for this. So I just want to give something back.    

Using the Code 

The native Windows message to scroll the listview is:

        const Int32 LVM_FIRST = 0x1000;
        const Int32 LVM_SCROLL = LVM_FIRST + 20;

        [DllImport("user32")]
        static extern IntPtr SendMessage(IntPtr Handle, Int32 msg, IntPtr wParam,
        IntPtr lParam);

        private void ScrollHorizontal(int pixelsToScroll)
        {
            SendMessage(this.Handle, LVM_SCROLL, (IntPtr)pixelsToScroll,
            IntPtr.Zero);
        }   

The public method to call with item to scroll to is as follows:

        /// <summary>
        /// Ensure visible of a ListViewItem and SubItem Index.
        /// </summary>
        /// <param name="item"></param>
        /// <param name="subItemIndex"></param>
        public void EnsureVisible(ListViewItem item, int subItemIndex)
        {
            if (item == null || subItemIndex > item.SubItems.Count - 1)
            {
                throw new ArgumentException();
            }

            // scroll to the item row.
            item.EnsureVisible();
            Rectangle bounds = item.SubItems[subItemIndex].Bounds;

            // need to set width from columnheader, first subitem includes
            // all subitems.
            bounds.Width = this.Columns[subItemIndex].Width;

            ScrollToRectangle(bounds);
        }

        /// <summary>
        /// Scrolls the listview.
        /// </summary>
        /// <param name="bounds"></param>
        private void ScrollToRectangle(Rectangle bounds)
        {
            int scrollToLeft = bounds.X + bounds.Width + MARGIN;
            if (scrollToLeft > this.Bounds.Width)
            {
                this.ScrollHorizontal(scrollToLeft - this.Bounds.Width);
            }
            else
            {
                int scrollToRight = bounds.X - MARGIN;
                if (scrollToRight < 0)
                {
                    this.ScrollHorizontal(scrollToRight);
                }
            }
        }
    }

History

• 30^th September, 2008: Initial post