title: How to prevent screen reader focus (not referring to keyboard focus) from leaving predefined area (e.g., modal)
body: <p>I've been trying to figure out how to contain the screen reader focus within a certain area.  When I say screen reader focus, I don't mean the default browser focus that one can move with tabbing/shift-tabbing.  I predominantly implement accessibility while using Voiceover on Mac, and when you turn that on, a new focus box appears on the page and reads out the information that it is 'highlighting'.</p>
  
  <p>At that point if you were to tab, both the browser and the screenreader focus move concurrently.  Aside from tabbing to different focusable elements, you can also hold cmd + opt and keypress left and right to move the screen reader focus from element to element, regardless if one can tab to it.  That's the focus that I'm trying to contain.</p>
  
  <p>I've tried preventing cmd, opt, and arrow key key presses when the focus is on the last element that I want focusable, but the browser doesn't seem to recognize the screen reader focus.  And I believe that the keyboard disabling wouldn't work with the screen reader anyways, as it seems to work independently of the browser.</p>
  
  <p>I've also tried dynamically adding tabindex: -1 and aria-hidden: true to all other elements on the page when a modal appears.  This works when you turn on Voiceover after the fact; the screen reader focus does in fact get trapped.  However if the screen reader is on first, which likely will be the case in most user instances, the screen reader doesn't respect the dynamic change.  It's like the screen reader takes a 'snapshot' of the accessibility state as the page loads, and it doesn't respect new changes to the DOM.</p>
  
  <p>Anyone have any ideas?</p>