Uprev Google Input Tools.

third_party/google_input_tools/src/chrome/os/inputview/util.js

 // Copyright 2014 The ChromeOS IME Authors. All Rights Reserved.
 // limitations under the License.
 // See the License for the specific language governing permissions and
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // distributed under the License is distributed on an "AS-IS" BASIS,
 // Unless required by applicable law or agreed to in writing, software
 //
 //      http://www.apache.org/licenses/LICENSE-2.0
 //
 // You may obtain a copy of the License at
@@ skipping 311 matching lines @@
  * Returns the configuration file name from the keyboard code.
  *
  * @param {string} keyboardCode The keyboard code.
  * @return {string} The config file name which contains the keyset.
  */
 util.getConfigName = function(keyboardCode) {
   // Strips out all the suffixes in the keyboard code.
   return keyboardCode.replace(/\..*$/, '');
 };
 
+
+/**
+ * Checks that the word is a valid delete from the old to new context.
+ *
+ * @param {string} oldContext The old context.
+ * @param {string} newContext The new context.
+ * @param {string} deletionCandidate A possible word deletion.
+ *
+ * @return {boolean} Whether the deletion was valid.
+ */
+util.isPossibleDelete = function(
+    oldContext, newContext, deletionCandidate) {
+  // Check that deletionCandidate exists in oldContext. We don't check if it's a
+  // tail since our heuristic may have trimmed whitespace.
+  var rootEnd = oldContext.lastIndexOf(deletionCandidate);
+  if (rootEnd != -1) {
+    // Check that remaining text in root persisted in newContext.
+    var root = oldContext.slice(0, rootEnd);
+    return root == newContext.slice(-rootEnd);
+  }
+  return false;
+};
+
+
+/**
+ * Checks whether a letter deletion would cause the observed context transform.
+ *
+ * @param {string} oldContext The old context.
+ * @param {string} newContext The new context.
+ *
+ * @return {boolean} Whether the transform is valid.
+ */
+util.isLetterDelete = function(oldContext, newContext) {
+  if (oldContext == '') {
+    return false;
+  }
+  // Handle buffer overflow.
+  if (oldContext.length == newContext.length) {
+    return util.isLetterDelete(oldContext, newContext.slice(1));
+  }
+  return oldContext.length == newContext.length + 1 &&
+      oldContext.indexOf(newContext) == 0;
+};
+
+
+/**
+ * Checks whether a letter restoration would cause the observed context
+ * transform.
+ *
+ * @param {string} oldContext The old context.
+ * @param {string} newContext The new context.
+ *
+ * @return {boolean} Whether the transform is valid.
+ */
+util.isLetterRestore = function(oldContext, newContext) {
+  return util.isLetterDelete(newContext, oldContext);
+};
+
 });  // goog.scope