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

dart/site/try/src/interaction_manager.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.interaction_manager;
 
 import 'dart:html';
 
 import 'dart:convert' show
     JSON;
@@ skipping 218 matching lines @@
       : super.internal() {
     state = new InitialState(this);
     heartbeat = new Timer.periodic(HEARTBEAT_INTERVAL, onHeartbeat);
   }
 
   void onInput(Event event) => state.onInput(event);
 
   void onKeyUp(KeyboardEvent event) => state.onKeyUp(event);
 
   void onMutation(List<MutationRecord> mutations, MutationObserver observer) {
+    workAroundFirefoxBug();
     try {
       try {
         return state.onMutation(mutations, observer);
       } finally {
         // Discard any mutations during the observer, as these can lead to
         // infinite loop.
         observer.takeRecords();
       }
     } catch (error, stackTrace) {
       try {
@@ skipping 52 matching lines @@
   InteractionContext get context;
 
   // TODO(ahe): Remove this.
   Set<AnchorElement> get oldDiagnostics {
     throw 'Use context.oldDiagnostics instead';
   }
 
   void set state(InteractionState newState);
 
   void onStateChanged(InteractionState previous) {
-    print('State change ${previous.runtimeType} -> ${runtimeType}.');
   }
 
   void transitionToInitialState() {
     state = new InitialState(context);
   }
 }
 
 class InitialState extends InteractionState {
   final InteractionContext context;
   bool requestCodeCompletion = false;
 
   InitialState(this.context);
 
   void set state(InteractionState state) {
     InteractionState previous = context.state;
     if (previous != state) {
       context.state = state;
       state.onStateChanged(previous);
     }
   }
 
   void onInput(Event event) {
     state = new PendingInputState(context);
   }
 
   void onKeyUp(KeyboardEvent event) {
     if (computeHasModifier(event)) {
-      print('onKeyUp (modified)');
       onModifiedKeyUp(event);
     } else {
-      print('onKeyUp (unmodified)');
       onUnmodifiedKeyUp(event);
     }
   }
 
   void onModifiedKeyUp(KeyboardEvent event) {
     if (event.getModifierState("Shift")) return onShiftedKeyUp(event);
     switch (event.keyCode) {
       case KeyCode.S:
         // Disable Ctrl-S, Cmd-S, etc. We have observed users hitting these
         // keys often when using Try Dart and getting frustrated.
@@ skipping 53 matching lines @@
 
     // This is a hack to get Safari (iOS) to send mutation events on
     // contenteditable.
     // TODO(ahe): Move to onInput?
     var newDiv = new DivElement();
     hackDiv.replaceWith(newDiv);
     hackDiv = newDiv;
   }
 
   void onMutation(List<MutationRecord> mutations, MutationObserver observer) {
-    print('onMutation');
-
     removeCodeCompletion();
 
     Selection selection = window.getSelection();
     TrySelection trySelection = new TrySelection(mainEditorPane, selection);
 
     Set<Node> normalizedNodes = new Set<Node>();
     for (MutationRecord record in mutations) {
       normalizeMutationRecord(record, trySelection, normalizedNodes);
     }
 
@@ skipping 21 matching lines @@
         for (String line in splitLines(currentText)) {
           List<Node> lineNodes = <Node>[];
           state = tokenizeAndHighlight(
               line, state, offset, trySelection, lineNodes);
           offset += line.length;
           nodes.add(makeLine(lineNodes, state));
         }
 
         node.parent.insertAllBefore(nodes, node);
         node.remove();
-        trySelection.adjust(selection);
+        if (mainEditorPane.contains(trySelection.anchorNode)) {
+          // Sometimes the anchor node is removed by the above call. This has
+          // only been observed in Firefox, and is hard to reproduce.
+          trySelection.adjust(selection);
+        }
 
         // TODO(ahe): We know almost exactly what has changed.  It could be
         // more efficient to only communicate what changed.
         context.currentCompilationUnit.content = getText(mainEditorPane);
 
         // Discard highlighting mutations.
         observer.takeRecords();
         return;
       }
     }
@@ skipping 729 matching lines @@
   }
   if (!record.removedNodes.isEmpty) {
     var first = record.removedNodes.first;
     var line = findLine(record.target);
 
     if (first is Text && first.data=="\n" && line.nextNode != null) {
       normalizedNodes.add(line.nextNode);
     }
     normalizedNodes.add(line);
   }
-  if (record.type == "characterData") {
+  if (record.type == "characterData" && record.target.parent != null) {
+    // At least Firefox sends a "characterData" record whose target is the
+    // deleted text node. It also sends a record where "removedNodes" isn't
+    // empty whose target is the parent (which we are interested in).
     normalizedNodes.add(findLine(record.target));
   }
 }
 
 // Finds the line of [node] (a parent node with CSS class 'lineNumber').
 // If no such parent exists, return mainEditorPane if it is a parent.
 // Otherwise return [node].
 Node findLine(Node node) {
   for (Node n = node; n != null; n = n.parent) {
     if (n is Element && n.classes.contains('lineNumber')) return n;
@@ skipping 32 matching lines @@
 bool isCompilerStageMarker(String message) {
   return
       message.startsWith('Package root is ') ||
       message.startsWith('Compiling ') ||
       message == "Resolving..." ||
       message.startsWith('Resolved ') ||
       message == "Inferring types..." ||
       message == "Compiling..." ||
       message.startsWith('Compiled ');
 }
+
+void workAroundFirefoxBug() {
+  Selection selection = window.getSelection();
+  if (!isCollapsed(selection)) return;
+  Node node = selection.anchorNode;
+  int offset = selection.anchorOffset;
+  if (selection.anchorNode is Element && selection.anchorOffset != 0) {
+    // In some cases, Firefox reports the wrong anchorOffset (always seems to
+    // be 6) when anchorNode is an Element. Moving the cursor back and forth
+    // adjusts the anchorOffset.
+    // Safari can also reach this code, but the offset isn't wrong, just
+    // inconsistent.  After moving the cursor back and forth, Safari will make
+    // the offset relative to a text node.
+    selection
+        ..modify('move', 'backward', 'character')
+        ..modify('move', 'forward', 'character');
+    print('Selection adjusted $node@$offset -> '
+          '${selection.anchorNode}@${selection.anchorOffset}.');
+  }
+}