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EnsureVisible for ListViewSubItem

, 30 Sep 2008
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Scroll horizontally in a ListView to ensure visibility of a subitem

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:

        /// <span class="code-SummaryComment"><summary></span>
        /// Ensure visible of a ListViewItem and SubItem Index.
        /// <span class="code-SummaryComment"></summary></span>
        /// <span class="code-SummaryComment"><param name="item"></param></span>
        /// <span class="code-SummaryComment"><param name="subItemIndex"></param></span>
        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);
        }

        /// <span class="code-SummaryComment"><summary></span>
        /// Scrolls the listview.
        /// <span class="code-SummaryComment"></summary></span>
        /// <span class="code-SummaryComment"><param name="bounds"></param></span>
        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

  • 30th September, 2008: Initial post

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

M Palmér
Software Developer (Senior)
Sweden Sweden
No Biography provided

Comments and Discussions

 
QuestionThanks Pinmemberjonbakari26-Apr-14 18:41 
GeneralPRECISELY what I needed!!! Pinmemberleward4-Dec-08 8:35 
QuestionWhere is the "MARGIN" defined ? Pinmembertal_segal6-Oct-08 20:54 
AnswerRe: Where is the "MARGIN" defined ? PinmemberM Palmér17-Oct-08 12:21 
GeneralThanks. PinmemberIlíon1-Oct-08 3:31 
GeneralRe: Thanks. PinmemberM Palmér2-Oct-08 10:47 

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