title: How to render (bitmap) only part of a Visual?
body: <p>I must print a displayed TreeView.</p>
  
  <p>Rendering the root TreeViewItem to bitmap, gives me an image of the whole (even non visible nodes) tree. Then I split the bitmap in "pages" to be printed. The rendering code:</p>
  
  <pre><code>m_Bitmap = new RenderTargetBitmap((int)l_RootTreeViewItem.ActualHeightDesiredSize.Width,
                                    (int)l_RootTreeViewItem.ActualHeight, 96, 96,
                                    PixelFormats.Pbgra32);
  
  m_Bitmap.Render(l_RootTreeViewItem);
  </code></pre>
  
  <p>Works well for small size trees. If the tree is large, <strong>RenderTargetBitmap</strong> results in <strong>"Out Of Memory"</strong> Exception. </p>
  
  <p>So, the idea is to render only parts of the visual to avoid memory problems. A <strong>Render</strong> method where I can choose which part of visual to render will be perfect...</p>
  
  <pre><code>m_Bitmap.Render(l_RootTreeViewItem, xOffset, yOffset, width, height);
  </code></pre>
  
  <p>... but doesn't exist. Is there some way to do that ?</p>