I needed to provide special handling for a large flyout panel in our application. I wanted to resize and reposition the panel if it was undocked in a way that would extend it beyond workable monitor boundaries. This might happen if you unplugged a laptop say, or just positioned the panel mostly off the screen.

I ended up handling this in the ToolWindowLoaded event. I may end up tweaking the size and position code a bit, but it seems to work well with the WPF 10.3 libraries we're using. Here's my sample handler, hope this helps someone out.

// fired when a flyout tab is floated by the user
private void OnToolWindowLoaded(object sender, PaneToolWindowEventArgs e)
{
  PaneToolWindow toolWindow = e.Window;

  // size restrictions when floating one of the flyout panels
  if ((toolWindow.Pane != null) && (toolWindow.Pane.Panes != null)) {

    var position = 10; // left or top position if we move the window
    var margin = 50; // margin if we need to resize or reposition
    // Primary screen height accounts for taskbar, virtual screen width for multiple monitors
    var maxHeight = SystemParameters.MaximizedPrimaryScreenHeight - margin - position;
    var maxWidth = SystemParameters.VirtualScreenWidth - margin - position;

    // Limit the size of the map pane when flown
    if (toolWindow.Height > maxHeight) {
      toolWindow.Height = maxHeight;
    }
    if (toolWindow.Width > maxWidth) {
      toolWindow.Width = maxWidth;
    }

    // Don't permit the map pane to position itself outside the monitor boundaries
    if ((toolWindow.Top < 0) ||
        ((toolWindow.Top + toolWindow.Height) > SystemParameters.MaximizedPrimaryScreenHeight)) {
          toolWindow.Top = position;
    }
    if ((toolWindow.Left < 0) ||
        ((toolWindow.Left + toolWindow.Width) > SystemParameters.VirtualScreenWidth)) {
          toolWindow.Left = position;
    }
  }
}