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Scroll multiple RichTextBoxes (or TextBoxes) in unison (synchronized scrolling).

/ Published in: C#
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This is useful for WinForm apps with multiple TextBoxes that need to be scrolled in unison. Similar applications are diff GUIs that show 2 or more files side-by-side, where each window needs to be scrolled in unison.

The approach below is a simpler alternative to http://stackoverflow.com/questions/1827323/c-synchronize-scroll-position-of-two-richtextboxes

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  1. /// Subclass RichTextBox to add the capability to bind scrolling for multiple RichTextBoxs.
  2.    /// This is useful for 'parallel' RTBs that require synchronized scrolling.
  3.    /// Taken from https://gist.github.com/593809
  4.    /// Added WM_HSCROLL 
  5.    /// Added BindScroll() to form a two-way linkage between RichTextBoxes.
  6.    /// Example usage showing how to bind 3 RichTextBoxes together:
  7.    ///    rtb1.BindScroll(rtb2);
  8.    ///    rtb2.BindScroll(rtb3);
  9.    ///    rtb3.BindScroll(rtb1);
  10.    class RichTextBoxSynchronizedScroll : RichTextBox
  11.    {
  12.  
  13.       private const int WM_VSCROLL = 0x115;
  14.       private const int WM_HSCROLL = 0x114;
  15.  
  16.       private List<RichTextBoxSynchronizedScroll> peers = new List<RichTextBoxSynchronizedScroll>();
  17.  
  18.       /// <summary>
  19.       /// Establish a 2-way binding between RTBs for scrolling.
  20.       /// </summary>
  21.       /// <param name="arg">Another RTB</param>
  22.       public void BindScroll( RichTextBoxSynchronizedScroll arg )
  23.       {
  24.          if ( peers.Contains( arg ) || arg==this ) { return; }
  25.          peers.Add( arg );
  26.          arg.BindScroll(this);
  27.       }
  28.  
  29.       private void DirectWndProc(ref Message m)
  30.       {
  31.          base.WndProc(ref m);
  32.       }
  33.  
  34.       protected override void WndProc(ref Message m)
  35.       {
  36.          if (m.Msg == WM_VSCROLL || m.Msg == WM_HSCROLL )
  37.          {
  38.             foreach (RichTextBoxSynchronizedScroll peer in this.peers)
  39.             {
  40.                Message peerMessage = Message.Create(peer.Handle, m.Msg, m.WParam, m.LParam);
  41.                peer.DirectWndProc(ref peerMessage);
  42.             }
  43.          }
  44.  
  45.          base.WndProc(ref m);
  46.       }
  47.    }

URL: /gist.github.com/593809

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