chrome/test/chromedriver/js/focus.js

   1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 function focus(element) {
   6   // Focus the target element in order to send keys to it.
   7   // First, the currently active element is blurred, if it is different from
   8   // the target element. We do not want to blur an element unnecessarily,
   9   // because this may cause us to lose the current cursor position in the
  10   // element.
  11   // Secondly, we focus the target element.
  12   // Thirdly, if the target element is newly focused and is a text input, we
  13   // set the cursor position at the end.
  14   // Fourthly, we check if the new active element is the target element. If not,
  15   // we throw an error.
  16   // Additional notes:
  17   //   - |document.activeElement| is the currently focused element, or body if
  18   //     no element is focused
  19   //   - Even if |document.hasFocus()| returns true and the active element is
  20   //     the body, sometimes we still need to focus the body element for send
  21   //     keys to work. Not sure why
  22   //   - You cannot focus a descendant of a content editable node
  23   //   - V8 throws a TypeError when calling setSelectionRange for a non-text
  24   //     input, which still have setSelectionRange defined. For chrome 29+, V8
  25   //     throws a DOMException with code InvalidStateError.
  26   var doc = element.ownerDocument || element;
  27   var prevActiveElement = doc.activeElement;
  28   if (element != prevActiveElement && prevActiveElement)
  29     prevActiveElement.blur();
  30   element.focus();
  31   if (element != prevActiveElement && element.value &&
  32       element.value.length && element.setSelectionRange) {
  33     try {
  34       element.setSelectionRange(element.value.length, element.value.length);
  35     } catch (error) {
  36       if (!(error instanceof TypeError) && !(error instanceof DOMException &&
  37           error.code == DOMException.INVALID_STATE_ERR))
  38         throw error;
  39     }
  40   }
  41
  42   var activeElement = doc.activeElement;
  43   // If the element is in a shadow DOM, then as far as the document is
  44   // concerned, the shadow host is the active element. We need to go through the
  45   // tree of shadow DOMs to check that the element we gave focus to is now
  46   // active.
  47   if (element != activeElement) {
  48     var shadowRoot = activeElement.shadowRoot;
  49     while (shadowRoot) {
  50       var activeElement = shadowRoot.activeElement;
  51       if (element == activeElement) {
  52         // the shadow DOM's active element is our requested element. We're good.
  53         break;
  54       }
  55       // The shadow DOM's active element isn't our requested element, check to
  56       // see if there's a nested shadow DOM.
  57       shadowRoot = activeElement.shadowRoot;
  58     }
  59   }
  60   if (element != activeElement)
  61     throw new Error('cannot focus element');
  62 }