Fix issues that broke editing on browsers without Shadow DOM support.

dart/site/try/src/selection.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library trydart.selection;
 
 import 'dart:html' show
     CharacterData,
+    Element,
     Node,
     NodeFilter,
     Selection,
     Text,
     TreeWalker;
 
+import 'shadow_root.dart' show
+    WALKER_RETURN,
+    walkNodes;
+
 import 'decoration.dart';
 
 class TrySelection {
   final Node root;
   Node anchorNode;
   int anchorOffset;
 
   String text;
   int globalOffset = -1;
 
   TrySelection(this.root, Selection selection)
       : anchorNode = isCollapsed(selection) ? selection.anchorNode : null,
         anchorOffset = isCollapsed(selection) ? selection.anchorOffset : -1;
 
   TrySelection.empty(this.root)
       : anchorNode = null,
         anchorOffset = -1;
 
   Text addNodeFromSubstring(int start,
                             int end,
                             List<Node> nodes,
                             [Decoration decoration]) {
-    if (start == end) return null;
-
     Text textNode = new Text(text.substring(start, end));
 
     if (start <= globalOffset && globalOffset <= end) {
       anchorNode = textNode;
       anchorOffset = globalOffset - start;
     }
 
     nodes.add(decoration == null ? textNode : decoration.applyTo(textNode));
 
     return textNode;
@@ skipping 14 matching lines @@
     return new TrySelection.empty(root)
         ..anchorNode = anchorNode
         ..anchorOffset = anchorOffset;
   }
 
   /// Computes the global offset, that is, the offset from [root].
   static int computeGlobalOffset(Node root, Node anchorNode, int anchorOffset) {
     if (anchorOffset == -1) return -1;
 
     int offset = 0;
-    TreeWalker walker = new TreeWalker(root, NodeFilter.SHOW_TEXT);
-    for (Node node = walker.nextNode();
-         node != null;
-         node = walker.nextNode()) {
-      CharacterData text = node;
-      if (anchorNode == text) {

[ahe, 2014/06/27 11:23:28]

This assumed that the anchorNode would always be a text node. Naturally, the
globalOffset was wrong, and consequently the cursor would jump "randomly" around
when I added syntax highlighting.

-        return anchorOffset + offset;
+    bool found = false;
+    walkNodes(root, (Node node) {
+      if (anchorNode == node) {
+        offset += anchorOffset;
+        found = true;
+        return WALKER_RETURN;
       }
-      offset += text.data.length;
-    }
-
-    return -1;
+      switch (node.nodeType) {
+        case Node.CDATA_SECTION_NODE:
+        case Node.TEXT_NODE:
+          CharacterData text = node;
+          offset += text.data.length;
+          break;
+      }
+    });
+    return found ? offset : -1;
   }
 }
 
 bool isCollapsed(Selection selection) {
   // Firefox and Chrome don't agree on if the selection is collapsed if there
   // is no node selected.
   return selection.isCollapsed && selection.anchorNode != null;
 }