title: NSScrollView in NSPrintOperation accessory view doesn't scroll properly
body: <p>I have to do a bit of processing before my app can start printing, so I do that on a thread, and once it is all done, I do</p>
  
  <pre><code>dispatch_async(dispatch_get_main_queue(),^(){
      ULIPrintableView *viewForPrinting = [[ULIPrintableView alloc] initWithData:data];
      NSPrintOperation *operation = [NSPrintOperation printOperationWithView:viewForPrinting];
      NSPrintPanel *panel = operation.printPanel;
      ULIPrintAccessoryViewController *settingsVC = [ULIPrintAccessoryViewController new];
      viewForPrinting.printOperation = operation;
      settingsVC.printView = viewForPrinting;
      [panel addAccessoryController:settingsVC];
      [operation runOperation];
  });
  </code></pre>
  
  <p>All works fine, except that for an NSScrollView (wrapping an NSTableView) in the accessory view.</p>
  
  <p>That view scrolls perfectly with a regular wired PC mouse attached to the Mac, but with an Apple trackpad (both MacBook or the external one) and two-finger scrolling, the scroll view does not update until you remove your fingers from the trackpad.</p>
  
  <p>It seems as if some sort of touch-moved events were not being delivered.</p>
  
  <p>If I change the last line in the block from <code>-runOperation</code> to <code>-runOperationModalForWindow:delegate:didRunSelector:contextInfo:</code> scrolling is OK again, but I don't really have a window I could show this sheet on in my use case.</p>
  
  <p>If I call either runOperation method directly instead of doing my threading the scroll view scrolls fine.</p>