limit tabbing to top modal

this limits tab navigation using the same basic approach bootstrap 3
uses, but with no bootstrap. To work perfectly, elements should have
tabindex defined. If not, you may get the address bar included in your
tab cycle. Works in Chrome, FF, IE8 & 9. Did not test 10. No tests
yet...

src/modal/modal.js

@@ -145,6 +145,45 @@ angular.module('ui.bootstrap.modal', [])
         modalWindow.modalScope.$destroy();
       }
 
+           // rough implementation of jquery .has()
+      function modalContainsElement(modal, element) {
+         var isChild = false;
+
+         var curElement = element;
+         while (curElement && curElement.localName !== 'html') {
+            if (curElement === modal.value.modalDomEl[0]) {
+               isChild = true;
+            }
+            curElement = curElement.parentElement;
+         }
+         return isChild;
+      }
+
+      // recursively search the DOM tree to find the first input or TEXTAREA type element so we can focus on it.
+      // you can uncomment the console calls in Chrome to see a nicely indented trace.
+      function firstInputOf(domEl, level) {
+         var firstInput = null;
+         //console.group('Level ' + level);
+         for (var i = 0; i < domEl.children.length; i++) {
+            var child = domEl.children[i];
+            //console.log('Level ' + level + ' Child #' + i + ': ' + child.tagName + ', ' + child.className);
+            //console.log();
+            if (child.children.length > 0) { // this child has potential, look for a field
+               firstInput = firstInputOf(child, level + 1);
+            }
+            if (firstInput !== null) {
+               break; // bubble any recursive results right up
+            }
+            if ((child.tagName == 'INPUT' || child.tagName == 'TEXTAREA') && !child.hidden) {
+               firstInput = child; // found it
+               break;
+            }
+         }
+         //console.log(firstInput ? 'FOUND IT: ' + firstInput.className : 'DID NOT FIND IT');
+         //console.groupEnd();
+         return firstInput; // no children returned anything
+      }
+
       $document.bind('keydown', function (evt) {
         var modal;
 
@@ -175,6 +214,24 @@ angular.module('ui.bootstrap.modal', [])
         var modalDomEl = $compile(angularDomEl)(modal.scope);
         openedWindows.top().value.modalDomEl = modalDomEl;
         body.append(modalDomEl);
+
+      //  unfortunately, not using jquery so we will wipe out existing focusin handlers, not just ours.
+      //  Needed to stop handler creep.
+      $document.unbind('focusin');
+
+      $document.bind('focusin', function (evt) {
+         var win;
+         // have to get this fresh because modalDomEl is just at template if you get it at function def
+         win = openedWindows.top();
+
+         var elementAboutToReceiveFocus = evt.target;
+         if (!modalContainsElement(win, elementAboutToReceiveFocus)) {
+            var firstInput = firstInputOf(win.value.modalDomEl[0], 0);
+            if (firstInput !== elementAboutToReceiveFocus && firstInput !== null) {
+               firstInput.focus();
+            }
+         }
+      });
 
         if (backdropIndex() >= 0 && !backdropDomEl) {
             backdropjqLiteEl = angular.element('<div modal-backdrop></div>');