Implement ChromeVox next/previous line, link, and heading.

chrome/browser/resources/chromeos/chromevox/cvox2/background/automation_util.js

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/**
+ * @fileoverview ChromeVox utilities for the automation extension API.
+ */
+
+goog.provide('cvox2.AutomationPredicates');
+goog.provide('cvox2.AutomationUtil');
+
+/**
+ * @constructor
+ */
+cvox2.AutomationPredicates = function() {};
+
+/**
+ * Constructs a predicate given a role.
+ * @param {string} role
+ * @return {function(AutomationNode) : boolean}
+ */
+cvox2.AutomationPredicates.makeRolePredicate = function(role) {
+  return function(node) {
+    return node.role == role;
+  };
+};
+
+/** @type {function(AutomationNode) : boolean} */
+cvox2.AutomationPredicates.heading =
+    cvox2.AutomationPredicates.makeRolePredicate(
+        chrome.automation.RoleType.heading);
+/** @type {function(AutomationNode) : boolean} */
+cvox2.AutomationPredicates.inlineTextBox =
+    cvox2.AutomationPredicates.makeRolePredicate(
+        chrome.automation.RoleType.inlineTextBox);
+/** @type {function(AutomationNode) : boolean} */
+cvox2.AutomationPredicates.link =
+    cvox2.AutomationPredicates.makeRolePredicate(
+        chrome.automation.RoleType.link);
+
+/**
+ * @constructor
+ */
+cvox2.AutomationUtil = function() {};
+
+/**
+ * Find a node in subtree of |cur| satisfying |pred| using pre-order traversal.
+ * @param {AutomationNode} cur Node to begin the search from.
+ * @param {boolean} r False to search forward (left to right), true to search

[dmazzoni, 2014/09/29 06:06:17]

Let's make the type an enum rather than boolean, and the parameter name 'dir'
instead of 'r'. It's still very short and concise but doesn't require you to
mentall remember what direction is true or false. It also won't require 2 lines
of documentation. Here's my specific idea:

/** @enum **/
cvox.Dir = {
  FORWARDS,
  BACKWARDS
}

 * @param {cvox.Direction} dir The direction to search.

+ * backward (right to left).
+ * @param {function(AutomationNode) : boolean} pred A predicate to apply to a
+ * candidate node.
+ * @return {AutomationNode}
+ */
+cvox2.AutomationUtil.findNodePre = function(cur, r, pred) {
+  if (pred(cur))
+    return cur;
+
+  var child = r ? cur.lastChild() : cur.firstChild();
+  while (child) {
+    var ret = cvox2.AutomationUtil.findNodePre(child, r, pred);
+    if (ret)
+      return ret;
+    child = r ? child.previousSibling() : child.nextSibling();
+  }
+};
+
+/**
+ * Find a node in subtree of |cur| satisfying |pred| using post-order traversal.
+ * @param {AutomationNode} cur Node to begin the search from.
+ * @param {boolean} r False to search forward (left to right), true to search
+ * backward (right to left).
+ * @param {function(AutomationNode) : boolean} pred A predicate to apply to a
+ * candidate node.
+ * @return {AutomationNode}
+ */
+cvox2.AutomationUtil.findNodePost = function(cur, r, pred) {
+  var child = r ? cur.lastChild() : cur.firstChild();
+  while (child) {
+    var ret = cvox2.AutomationUtil.findNodePost(child, r, pred);
+    if (ret)
+      return ret;
+    child = r ? child.previousSibling() : child.nextSibling();
+  }
+
+  if (pred(cur))
+    return cur;
+};
+
+/**
+ * Find the directed next node that is either an immediate sibling or a sibling

[dmazzoni, 2014/09/29 06:06:17]

By "directed next" do you mean, either the next node, or the previous node,
depending on 'r'? I just find the wording confusing. How about: Find the next
node in the given direction that is...

[David Tseng, 2014/09/29 17:05:23]

Done.

+ * of an ancestor.
+ * @param {AutomationNode} cur Node to start search from.
+ * @param {boolean} r False to search forward (left to right), true to search
+ * backward (right to left).

[dmazzoni, 2014/09/29 06:06:17]

nit: indent 4 spaces - and elsewhere for additional lines of description for the
same parameter.

[David Tseng, 2014/09/29 17:05:23]

Done.

+ * @return {AutomationNode}
+ */
+cvox2.AutomationUtil.findNextSubtree = function(cur, r) {
+  while (cur) {
+    var next = r ? cur.previousSibling() : cur.nextSibling();
+    if (next)
+      return next;
+
+    cur = cur.parent();
+  }
+};
+
+/**
+ * Find the directed next node in depth first order.
+ * @param {AutomationNode} cur Node to begin the search from.
+ * @param {boolean} r False to search forward (left to right), true to search
+ * backward (right to left).
+ * @param {function(AutomationNode) : boolean} pred A predicate to apply to a
+ * candidate node.
+ * @return {AutomationNode}
+ */
+cvox2.AutomationUtil.findNextNode = function(cur, r, pred) {
+  var next = cur;
+  do {
+    if (!(next = cvox2.AutomationUtil.findNextSubtree(cur, r)))
+      return null;
+    cur = next;
+    next = cvox2.AutomationUtil.findNodePre(next, r, pred);
+  } while (!next);
+  return next;
+};