dart:html perf optimization based on runing Dromaeo benchmarks

lib/dom/templates/html/impl/impl_Document.darttemplate

+// Copyright (c) 2012, 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.
+
+class $CLASSNAME extends _NodeImpl

[nweiz, 2012/03/28 01:16:17]

Why not "class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC"?

[Jacob, 2012/03/28 17:52:54]

Because it extends _NodeImpl not _ElementImpl

Also, we force HTMLDocument as the native class rather than Document

We could hard code in the generator but I believe it is nicer to keep the hard
coded logic in the template for hard coded functionality that is a 1-off.

+    implements Document
+$if FROG
+    native "*HTMLDocument"
+$endif
+    {
+
+$!MEMBERS
+  // TODO(jacobr): implement all Element methods not on Document. 
+
+  _ElementImpl query(String selectors) {
+    if (const RegExp("^#\\w+\$").hasMatch(selectors)) {
+      return $dom_getElementById(selectors.substring(1));

[nweiz, 2012/03/28 01:16:17]

Is this really faster? That's kind of depressing.

How sure are we that Javascript's notion of word characters is identical to
CSS's notion?

[Jacob, 2012/03/28 17:52:54]

Sad but true.... This is a LOT faster for getElementById on Chrome and other
browsers.

You're right. I missed an edge case... document.getElementById('23') works but
document.querySelector('#23') throws an exception
changed the regexp to only special case for element ids that start with a
letter.

[nweiz, 2012/03/28 20:29:33]

I'm not sure how much we want to care about false negatives, but this misses ids
that start with "_" as well as non-ascii characters and escape sequences. "_" at
least would be easy to support.

[Jacob, 2012/03/28 21:01:30]

I've added a comment that this has false negatives but that is fine.  False
positives cause logic bugs, false negatives just make the code a little slower
than it could be. Added _ to the RegExp as I agree that could possibly be a
common case and there is little cost to check for it. 

On 2012/03/28 20:29:33, nweiz wrote:

+    }
+    return $dom_querySelector(selectors);
+  }
+
+  _ElementImpl $dom_querySelector(String selectors) native "return this.querySelector(selectors);";

[nweiz, 2012/03/28 01:16:17]

Line length. Also, why isn't this autogenerated?

[Jacob, 2012/03/28 17:52:54]

Obeying line length for these native lines does more harm than good.... Also,
all of the autogen native lines in the output will be >80 chars anyway.  This
isn't auto generated yet because it is marked as hidden in systemhtml.py.  added
a todo to clean that up.

+
+  ElementList queryAll(String selectors) {
+    if (const RegExp("""^\\[name=["'][^'"]+['"]\\]\$""").hasMatch(selectors)) {
+      final mutableMatches = $dom_getElementsByName(
+          selectors.substring(7,selectors.length - 2));
+      int len = mutableMatches.length;
+      final copyOfMatches = new List<Element>(len);
+      for (int i = 0; i < len; ++i) {
+        copyOfMatches[i] = mutableMatches[i];
+      }
+      return new _FrozenElementList._wrap(copyOfMatches);
+    } else if (const RegExp("^[*a-zA-Z0-9]+\$").hasMatch(selectors)) {
+      final mutableMatches = $dom_getElementsByTagName(selectors);
+      int len = mutableMatches.length;
+      final copyOfMatches = new List<Element>(len);
+      for (int i = 0; i < len; ++i) {
+        copyOfMatches[i] = mutableMatches[i];
+      }
+      return new _FrozenElementList._wrap(copyOfMatches);
+    } else {
+      return new _FrozenElementList._wrap($dom_querySelectorAll(selectors));
+    }
+  }
+}