title: kCGErrorIllegalArgument: _CGSFindSharedWindow?
body: <p>While attempting to write a simple Cocoa/Applescript with a custom background (following this tutorial, <a href="http://www.mere-mortal-software.com/blog/details.php?d=2007-01-08" rel="noreferrer">http://www.mere-mortal-software.com/blog/details.php?d=2007-01-08</a>), I get the following error every now and then in the debugger:</p>
  
  <pre><code>Error&gt;: kCGErrorIllegalArgument: _CGSFindSharedWindow: WID 3162
  Media Center[10234] &lt;Error&gt;: kCGErrorFailure: Set a breakpoint @ CGErrorBreakpoint() to catch errors as they are logged.
  </code></pre>
  
  <p>So I set a breakpoint at <code>CGErrorBreakpoint</code> and I got the following results:</p>
  
  <pre><code>Thread 1, Queue : com.apple.main-thread
  #1  0x00007fff92ba4112 in CGSGlobalErrorv ()
  #2  0x00007fff92c7ca25 in _CGSFindSharedWindow ()
  #3  0x00007fff92b275a9 in _CGSWindowByID ()
  #4  0x00007fff92c2cdf9 in CGSOrderFrontConditionally ()
  #5  0x00007fff93ce1ecf in __-[NSApplication _copyBatchWindowOrderingPerformerForToken:release:]_block_invoke_2 ()
  #6  0x00007fff93d0f685 in -[NSPersistentUIManager resumeNormalWindowOrderingAndDrawing] ()
  #7  0x00007fff93d0f52f in -[NSPersistentUIManager tearDownStateRestorationApparatusAndResumeWindowOrdering] ()
  #8  0x00007fff93d0f374 in -[NSPersistentUIManager finishedRestoringWindowsWithZOrder:registerAsReady:completionHandler:] ()
  #9  0x00007fff944f25ed in __-[NSPersistentUIManager restoreAllPersistentStateWithTalagentWindows:registeringAsReadyWhenDone:completionHandler:]_block_invoke_3 ()
  #10 0x00007fff944f4080 in __-[NSPersistentUIManager restoreAllPersistentStateWithTalagentWindows:registeringAsReadyWhenDone:completionHandler:]_block_invoke_2 ()
  #11 0x00007fff93f323e8 in __-[NSApplication(NSPersistentUISupport) _restoreWindowWithRestoration:handler:]_block_invoke_1 ()
  #12 0x00007fff944f2760 in __-[NSApplication(NSPersistentUISupport) _restoreWindowWithRestoration:handler:]_block_invoke_3 ()
  #13 0x00007fff94c2e44c in __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ ()
  #14 0x00007fff94be6562 in __CFRunLoopDoBlocks ()
  #15 0x00007fff94c0e195 in __CFRunLoopRun ()
  #16 0x00007fff94c0dae6 in CFRunLoopRunSpecific ()
  #17 0x00007fff8cfdf3d3 in RunCurrentEventLoopInMode ()
  #18 0x00007fff8cfe658f in ReceiveNextEventCommon ()
  #19 0x00007fff8cfe64ca in BlockUntilNextEventMatchingListInMode ()
  #20 0x00007fff93cdc3f1 in _DPSNextEvent ()
  #21 0x00007fff93cdbcf5 in -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] ()
  #22 0x00007fff93cd862d in -[NSApplication run] ()
  Thread 2, Queue : (null)
  Thread 3, Queue : com.apple.libdispatch-manager
  Thread 4, Queue : (null)
  Thread 6, Queue : (null)
  Thread 7, Queue : (null)
  </code></pre>
  
  <p>I'm not entirely sure how to remedy this, and I'll provide more output info if requested.</p>
  
  <p>Edit: If you open the app while the dock is shown, I get the error. If the dock is not shown, it usually works.</p>