[gin] Introduce Wrappable::GetObjectTemplate

gin/wrappable.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef GIN_WRAPPABLE_H_
 #define GIN_WRAPPABLE_H_
 
 #include "base/template_util.h"
 #include "gin/converter.h"
 #include "gin/gin_export.h"
 #include "gin/public/wrapper_info.h"
 
 namespace gin {
 
 namespace internal {
 
 GIN_EXPORT void* FromV8Impl(v8::Isolate* isolate,
                             v8::Handle<v8::Value> val,
                             WrapperInfo* info);
 
 }  // namespace internal
 
 
 // Wrappable is a base class for C++ objects that have corresponding v8 wrapper
 // objects. To retain a Wrappable object on the stack, use a gin::Handle.
 //
 // USAGE:
 // // my_class.h
 // class MyClass : Wrappable<MyClass> {
+//  public:
+//   static WrapperInfo kWrapperInfo;
+//
+//  private:
+//   friend class Wrappable<MyClass>;
+//   static v8::Local<v8::ObjectTemplate> GetObjectTemplate(

[Aaron Boodman, 2013/12/16 16:44:26]

It's ok for this to be public now (I think before what was bothering me was that
the responsibility for calling it was with the user).

[Aaron Boodman, 2013/12/16 16:50:35]

Some classes don't want to have any methods or properties on the JS object --
they just use the JS wrapper for lifetime management.

For those cases it would be nice to have a default implementation of
GetObjectTemplate(). Can this be achieved without making GetObjectTemplate()
virtual by having an impl in WrapperBase? I forget how resolution would work in
that case.

[jochen (gone - plz use gerrit), 2013/12/17 14:32:31]

Done.

+//       v8::Isolate* isolate);
 //   ...
 // };
 //
 // // my_class.cc
-// INIT_WRAPABLE(MyClass);
+// WrapperInfo MyClass::kWrapperInfo = { kEmbedderNativeGin };
+//
+// v8::Local<v8::ObjectTemplate> MyClass::GetObjectTemplate(
+//     v8::Isolate* isolate) {
+//   return ObjectTemplateBuilder(isolate, &kWrapperInfo).Build();
+// }
 //
 // Subclasses should also typically have private constructors and expose a
 // static Create function that returns a gin::Handle. Forcing creators through
 // this static Create function will enforce that clients actually create a
 // wrapper for the object. If clients fail to create a wrapper for a wrappable
 // object, the object will leak because we use the weak callback from the
 // wrapper as the signal to delete the wrapped object.
 template<typename T>
 class Wrappable;
 
 
 // Non-template base class to share code between templates instances.
 class GIN_EXPORT WrappableBase {
  protected:
+  typedef v8::Local<v8::ObjectTemplate> (*TemplateBuilder)(v8::Isolate*);

[Aaron Boodman, 2013/12/16 16:44:26]

Confusing name since we also have ObjectTemplateBuilder. How about just
*GetObjectTemplateFunction

[jochen (gone - plz use gerrit), 2013/12/17 14:32:31]

Done.

+
   WrappableBase();
   virtual ~WrappableBase();
+
   v8::Handle<v8::Object> GetWrapperImpl(v8::Isolate* isolate,
-                                        WrapperInfo* wrapper_info);
-  v8::Handle<v8::Object> CreateWrapper(v8::Isolate* isolate,
-                                       WrapperInfo* wrapper_info);
-  v8::Persistent<v8::Object> wrapper_;  // Weak
+                                        WrapperInfo* wrapper_info,
+                                        TemplateBuilder builder);
 
  private:
   static void WeakCallback(
       const v8::WeakCallbackData<v8::Object, WrappableBase>& data);
 
+  v8::Handle<v8::Object> CreateWrapper(v8::Isolate* isolate,
+                                       WrapperInfo* wrapper_info,
+                                       TemplateBuilder builder);
+
+  v8::Persistent<v8::Object> wrapper_;  // Weak
+
   DISALLOW_COPY_AND_ASSIGN(WrappableBase);
 };
 
 
 template<typename T>
 class Wrappable : public WrappableBase {
  public:
   // Retrieve (or create) the v8 wrapper object cooresponding to this object.
   // To customize the wrapper created for a subclass, override GetWrapperInfo()
   // instead of overriding this function.
   v8::Handle<v8::Object> GetWrapper(v8::Isolate* isolate) {
-    return GetWrapperImpl(isolate, &T::kWrapperInfo);
+    return GetWrapperImpl(isolate, &T::kWrapperInfo, &T::GetObjectTemplate);
   }
 
  protected:
   Wrappable() {}
   virtual ~Wrappable() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(Wrappable);
 };
 
 
 // This converter handles any subclass of Wrappable.
 template<typename T>
 struct Converter<T*, typename base::enable_if<
                        base::is_convertible<T*, Wrappable<T>*>::value>::type> {
   static v8::Handle<v8::Value> ToV8(v8::Isolate* isolate, T* val) {
     return val->GetWrapper(isolate);
   }
 
   static bool FromV8(v8::Isolate* isolate, v8::Handle<v8::Value> val, T** out) {
     *out = static_cast<T*>(internal::FromV8Impl(isolate, val,
                                                 &T::kWrapperInfo));
     return *out != NULL;
   }
 };
 
 }  // namespace gin
 
 #endif  // GIN_WRAPPABLE_H_