From baf8bc49fda15cb850883ad186ad759446033bad Mon Sep 17 00:00:00 2001
From: Sean Lip <sll@google.com>
Date: Tue, 2 Aug 2016 16:43:27 -0700
Subject: [PATCH] Do a DFS to find the first available input field or button
 when the user presses the Enter key.

---
 accessible/tree.service.js | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/accessible/tree.service.js b/accessible/tree.service.js
index 3a96ad2a8..2c74b984a 100644
--- a/accessible/tree.service.js
+++ b/accessible/tree.service.js
@@ -259,13 +259,27 @@ blocklyApp.TreeService = ng.core
         if (e.keyCode == 13) {
           // Enter key. The user wants to interact with a button or an input
           // field.
-          var currentChild = activeDesc;
-          while (currentChild.children.length) {
-            currentChild = currentChild.children[0];
-            if (currentChild.tagName == 'BUTTON') {
-              currentChild.click();
-            } else if (currentChild.tagName == 'INPUT') {
-              currentChild.focus();
+          // Algorithm to find the field: do a DFS through the children until
+          // we find an INPUT or BUTTON element (in which case we use it).
+          // Truncate the search at child LI elements.
+          var dfsStack = Array.from(activeDesc.children);
+          while (dfsStack.length) {
+            var currentNode = dfsStack.shift();
+            if (currentNode.tagName == 'BUTTON') {
+              currentNode.click();
+              break;
+            } else if (currentNode.tagName == 'INPUT') {
+              currentNode.focus();
+              break;
+            } else if (currentNode.tagName == 'LI') {
+              continue;
+            }
+
+            if (currentNode.children) {
+              var reversedChildren = Array.from(currentNode.children).reverse();
+              reversedChildren.forEach(function(childNode) {
+                dfsStack.unshift(childNode);
+              });
             }
           }
         } else if (e.keyCode == 9) {