SetScrollInfo on PrintPreviewControl

• 2009年7月28日 22:49

   

   
  

  0
  I am working with a PrintPreviewControl. When it is zoomed in so that only a portion of the current page is shown scrollbars appear to allow the user to scroll over the entire page. I want to allow the user to scroll the image by clicking and dragging. I'm trying to use GetScrollInfo and SetScrollInfo but for some reason only one scroll bar is updated.
  
  I am using Visual Studio 2005 on Vista.
  
  Here is some sample code:
  
          Point dragOffset;
          private void printPreviewControl1_MouseDown(object sender, MouseEventArgs e) {
              dragOffset = e.Location;
          }
  
          private void printPreviewControl1_MouseMove(object sender, MouseEventArgs e) {
              if (e.Button == MouseButtons.Left) {
                  scroll(e.X - dragOffset.X, e.Y - dragOffset.Y);
                  dragOffset = e.Location;
                  printPreviewControl1.Invalidate();
                  printPreviewControl1.Refresh();
              }
          }
  
          private void scroll(int dx, int dy) {
              SCROLLINFO info = new SCROLLINFO();
              info.Size = Marshal.SizeOf(info);
              info.Mask = 0xff;
  
              GetScrollInfo(printPreviewControl1.Handle, SB_HORZ, ref info);
              info.Pos -= dx;
              SetScrollInfo(printPreviewControl1.Handle, SB_HORZ, ref info, true);
              PostMessageA((IntPtr)printPreviewControl1.Handle, WM_HSCROLL, SB_THUMBPOSITION + 0x10000 * info.Pos, 0);
             
              GetScrollInfo(printPreviewControl1.Handle, SB_VERT, ref info);
              info.Pos -= dy;
              SetScrollInfo(printPreviewControl1.Handle, SB_VERT, ref info, true);
              PostMessageA((IntPtr)printPreviewControl1.Handle, WM_VSCROLL, SB_THUMBPOSITION + 0x10000 * info.Pos, 0);
          }
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