Refactor the event-generation code to locate it in systemhtml.py.

client/dom/scripts/systemhtml.py

Index: client/dom/scripts/systemhtml.py
diff --git a/client/dom/scripts/systemhtml.py b/client/dom/scripts/systemhtml.py
index 4c4945780abf44ed016d8882e35531a62661add9..b4d28397af09468de4b61ad9e22b9f4c0cdb110e 100644
--- a/client/dom/scripts/systemhtml.py
+++ b/client/dom/scripts/systemhtml.py
@@ -383,6 +383,11 @@ _html_event_names = {
   'webkitTransitionEnd': 'transitionEnd'
 }
 
+# These classes require an explicit declaration for the "on" method even though
+# they don't declare any unique events, because the concrete class hierarchy
+# doesn't match the interface hierarchy.
+_html_explicit_event_classes = set(['DocumentFragment'])
+
 def _OnAttributeToEventName(on_method):
   event_name = on_method.id[2:]
   if event_name in _on_attribute_to_event_name_mapping:
@@ -496,6 +501,13 @@ class HtmlSystemShared(object):
   def _ImplClassName(self, type_name):
     return '_' + type_name + 'Impl'
 
+  def GetEventAttributes(self, interface):
+    events =  set([attr for attr in interface.attributes
+                   if self._generator._IsEventAttribute(interface, attr)])
+
+    if events or interface.id in _html_explicit_event_classes:
+      return events
+
 class HtmlSystem(System):
 
   def __init__(self, templates, database, emitters, output_dir, generator):
@@ -628,6 +640,12 @@ class HtmlDartInterfaceGenerator(DartInterfaceGenerator):
         CTOR=self._interface.id,
         TYPE=DartType(element_type))
 
+    events = self._shared.GetEventAttributes(self._interface)
+    if events == set():

[Jacob, 2012/03/08 18:38:09]

writing 
if events == set(): 
looks really odd
can you write
if len(events) > 0: 
  self.AddEventAttributes(events)
else:
  self.AddParentEvent()

instead?

[nweiz, 2012/03/08 20:47:16]

len(None) doesn't work, and I don't want to make the if statement have an extra
branch unnecessarily by checking for None early. "== set()" best expresses the
semantics here.

+      self.AddParentEvent()
+    elif events:
+      self.AddEventAttributes(events)
+
   def AddAttribute(self, getter, setter):
     html_getter_name = self._shared.RenameInHtmlLibrary(
       self._interface, getter.id, 'get:')
@@ -678,12 +696,23 @@ class HtmlDartInterfaceGenerator(DartInterfaceGenerator):
   def AddConstant(self, constant):
     self._EmitConstant(self._members_emitter, constant)
 
+  def AddParentEvent(self):
+    parent_event_classes = self._shared.GetParentsEventsClasses(
+        self._interface)
+    if len(parent_event_classes) != 1:
+      raise Exception('Only one parent event class allowed '
+          + self._interface.id)
+
+    self._members_emitter.Emit('\n  $TYPE get on();\n',
+                               TYPE=parent_event_classes[0])
+
   def AddEventAttributes(self, event_attrs):
     event_attrs = _DomToHtmlEvents(self._interface.id, event_attrs)
     self._shared._event_classes.add(self._interface.id)
     events_interface = self._interface.id + 'Events'
     self._members_emitter.Emit('\n  $TYPE get on();\n',
                                TYPE=events_interface)
+
     events_members = self._emitter.Emit(
         '\ninterface $INTERFACE extends $PARENTS {\n$!MEMBERS}\n',
         INTERFACE=events_interface,
@@ -758,6 +787,12 @@ class HtmlFrogClassGenerator(FrogInterfaceGenerator):
     if constructor_info:
       self._EmitFactoryProvider(interface_name, constructor_info)
 
+    events = self._shared.GetEventAttributes(self._interface)
+    if events == set():
+      self.AddParentEvent()
+    elif events:
+      self.AddEventAttributes(events)
+
   def _EmitFactoryProvider(self, interface_name, constructor_info):
     template_file = 'factoryprovider_%s.darttemplate' % interface_name
     template = self._system._templates.TryLoad(template_file)
@@ -982,6 +1017,19 @@ class HtmlFrogClassGenerator(FrogInterfaceGenerator):
           PARAMS=info.ParametersImplementationDeclaration(
               lambda type_name: self._NarrowInputType(type_name)))
 
+  def AddParentEvent(self):

[Jacob, 2012/03/08 18:38:09]

seems like there is duplicated code in AddParentEvent and AddEventAttributes.
Can you unify?

[nweiz, 2012/03/08 20:47:16]

Done.

+    parent_event_classes = self._shared.GetParentsEventsClasses(
+        self._interface)
+    if len(parent_event_classes) != 1:
+      raise Exception('Only one parent event class allowed '
+          + self._interface.id)
+
+    self._members_emitter.Emit(
+        '\n  $TYPE get on() =>\n    new $TYPE($EVENTTARGET);\n',
+        TYPE=parent_event_classes[0],
+        EVENTTARGET='_jsDocument' if self._interface.id == 'Document'
+            else 'this')
+
   def AddEventAttributes(self, event_attrs):
     event_attrs = _DomToHtmlEvents(self._interface.id, event_attrs)
     events_class = '_' + self._interface.id + 'EventsImpl'
@@ -1237,6 +1285,12 @@ class HtmlDartiumInterfaceGenerator(object):
     if constructor_info:
       self._EmitFactoryProvider(interface_name, constructor_info)
 
+    events = self._shared.GetEventAttributes(self._interface)
+    if events == set():
+      self.AddParentEvent()
+    elif events:
+      self.AddEventAttributes(events)
+
   def _EmitFactoryProvider(self, interface_name, constructor_info):
     template_file = 'factoryprovider_%s.darttemplate' % interface_name
     template = self._system._templates.TryLoad(template_file)
@@ -1349,6 +1403,23 @@ class HtmlDartiumInterfaceGenerator(object):
     self._SecondaryContext(interface)
     self.AddOperation(info)
 
+  def AddParentEvent(self):
+    parent_event_classes = self._shared.GetParentsEventsClasses(
+        self._interface)
+    if len(parent_event_classes) != 1:
+      raise Exception('Only one parent event class allowed '
+          + self._interface.id)
+
+    self._members_emitter.Emit(
+        '\n'
+        '  $TYPE get on() {\n'
+        '    if (_on == null) _on = new $TYPE($EVENTTARGET);\n'
+        '    return _on;\n'
+        '  }\n',
+        TYPE=parent_event_classes[0],
+        EVENTTARGET='_wrappedDocumentPtr' if self._interface.id == 'Document'
+            else 'this')
+
   def AddEventAttributes(self, event_attrs):
     event_attrs = _DomToHtmlEvents(self._interface.id, event_attrs)
     events_class = '_' + self._interface.id + 'EventsImpl'