Dispatch with conversion hooks

lib/html/src/dart2js_Conversions.dart

Index: lib/html/src/dart2js_Conversions.dart
diff --git a/lib/html/src/dart2js_Conversions.dart b/lib/html/src/dart2js_Conversions.dart
new file mode 100644
index 0000000000000000000000000000000000000000..e0e2ff2289a80ecb885b053eb6acb83d41b8d3d6
--- /dev/null
+++ b/lib/html/src/dart2js_Conversions.dart
@@ -0,0 +1,106 @@
+// 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.
+
+// Conversions for IDBKey.
+//
+// Per http://www.w3.org/TR/IndexedDB/#key-construct
+//
+// "A value is said to be a valid key if it is one of the following types: Array
+// JavaScript objects [ECMA-262], DOMString [WEBIDL], Date [ECMA-262] or float
+// [WEBIDL]. However Arrays are only valid keys if every item in the array is
+// defined and is a valid key (i.e. sparse arrays can not be valid keys) and if
+// the Array doesn't directly or indirectly contain itself. Any non-numeric
+// properties are ignored, and thus does not affect whether the Array is a valid
+// key. Additionally, if the value is of type float, it is only a valid key if
+// it is not NaN, and if the value is of type Date it is only a valid key if its
+// [[PrimitiveValue]] internal property, as defined by [ECMA-262], is not NaN."
+
+// What is required is to ensure that an Lists in the key are actually
+// JavaScript arrays, and any Dates are JavaScript Dates.
+
+/**
+ * Converts a native IDBKey into a Dart object.
+ *
+ * May return the original input.  May mutate the original input (but will be
+ * idempotent if mutation occurs).  It is assumed that this conversion happens
+ * on native IDBKeys on all paths that return IDBKeys from native DOM calls.
+ *
+ * If necessary, JavaScript Dates are converted into Dart Dates.
+ */
+_convertNativeToDart_IDBKey(nativeKey) {
+  // TODO: Implement.
+  // TODO: Cache conversion somewhere.
+  return nativeKey;
+}
+
+/**
+ * Converts a Dart object into a valid IDBKey.
+ *
+ * May return the original input.  Does not mutate input.
+ *
+ * If necessary, [dartKey] may be copied to ensure all lists are converted into
+ * JavaScript Arrays and Dart Dates into JavaScript Dates.
+ */
+
+_convertDartToNative_IDBKey(dartKey) {
+  // TODO: Implement.
+  // TODO: Cache conversion on object.
+  return dartKey;
+}
+
+
+// Conversions for ImageData
+//
+// On Firefox, the returned ImageData is a plain object.
+
+class _TypedImageData implements ImageData {
+  final Uint8ClampedArray data;
+  final int height;
+  final int width;
+
+  _TypedImageData(this.data, this.height, this.width);
+}
+
+ImageData _convertNativeToDart_ImageData(nativeImageData) {
+  if (nativeImageData is ImageData) return nativeImageData;
+
+  // On Firefox the above test fails because imagedata is a plain object.
+  // So we create a _TypedImageData.
+
+  return new _TypedImageData(
+      JS('var', '#.data', nativeImageData),
+      JS('var', '#.height', nativeImageData),
+      JS('var', '#.width', nativeImageData));
+}
+
+// We can get rid of this conversion if _TypedImageData implements the fields
+// with native names.
+_convertDartToNative_ImageData(ImageData imageData) {
+  if (imageData is _ImageDataImpl) return imageData;
+  return JS('Object', '{data: #, height: #, width: #}',
+            imageData.data, imageData.height, imageData.width);
+}
+
+
+/// Converts a JavaScript object with properties into a Dart Map.
+Map _convertNativeToDart_Dictionary(object) {
+  // TODO: Implement.
+  return object;
+}
+
+/// Converts a Dart map into a JavaScript object with properties.
+_convertDartToNative_Dictionary(Map dict) {
+  // TODO: Implement.
+  return dict;
+}
+
+
+/**
+ * Ensures that the input is a JavaScript Array.
+ *
+ * Creates a new JavaScript array if necessary, otherwise returns the original.
+ */
+List _convertDartToNative_StringArray(List<String> input) {
+  return input;
+}