Rebuild aura::Window's property system on top of mojo::View.

mojo/services/public/cpp/view_manager/view_property.h

+// Copyright 2014 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 MOJO_SERVICES_PUBLIC_CPP_VIEW_MANAGER_VIEW_PROPERTY_H_
+#define MOJO_SERVICES_PUBLIC_CPP_VIEW_MANAGER_VIEW_PROPERTY_H_
+
+#include "base/basictypes.h"
+
+// This header should be included by code that defines ViewProperties. It
+// should not be included by code that only gets and sets ViewProperties.
+//
+// To define a new ViewProperty:
+//
+//  #include "mojo/services/public/cpp/view_manager/view_property.h"
+//
+//  DECLARE_EXPORTED_VIEW_PROPERTY_TYPE(FOO_EXPORT, MyType);
+//  namespace foo {
+//    // Use this to define an exported property that is premitive,
+//    // or a pointer you don't want automatically deleted.
+//    DEFINE_VIEW_PROPERTY_KEY(MyType, kMyKey, MyDefault);
+//
+//    // Use this to define an exported property whose value is a heap
+//    // allocated object, and has to be owned and freed by the view.
+//    DEFINE_OWNED_VIEW_PROPERTY_KEY(gfx::Rect, kRestoreBoundsKey, nullptr);
+//
+//    // Use this to define a non exported property that is primitive,
+//    // or a pointer you don't want to automatically deleted, and is used
+//    // only in a specific file. This will define the property in an unnamed
+//    // namespace which cannot be accessed from another file.
+//    DEFINE_LOCAL_VIEW_PROPERTY_KEY(MyType, kMyKey, MyDefault);
+//
+//  }  // foo namespace
+//
+// To define a new type used for ViewProperty.
+//
+//  // outside all namespaces:
+//  DECLARE_EXPORTED_VIEW_PROPERTY_TYPE(FOO_EXPORT, MyType)
+//
+// If a property type is not exported, use DECLARE_VIEW_PROPERTY_TYPE(MyType)
+// which is a shorthand for DECLARE_EXPORTED_VIEW_PROPERTY_TYPE(, MyType).
+
+namespace mojo {
+namespace {
+
+// No single new-style cast works for every conversion to/from int64, so we
+// need this helper class. A third specialization is needed for bool because
+// MSVC warning C4800 (forcing value to bool) is not suppressed by an explicit
+// cast (!).
+template <typename T>
+class ViewPropertyCaster {
+ public:
+  static int64 ToInt64(T x) { return static_cast<int64>(x); }
+  static T FromInt64(int64 x) { return static_cast<T>(x); }
+};
+template <typename T>
+class ViewPropertyCaster<T*> {
+ public:
+  static int64 ToInt64(T* x) { return reinterpret_cast<int64>(x); }
+  static T* FromInt64(int64 x) { return reinterpret_cast<T*>(x); }
+};
+template <>
+class ViewPropertyCaster<bool> {
+ public:
+  static int64 ToInt64(bool x) { return static_cast<int64>(x); }
+  static bool FromInt64(int64 x) { return x != 0; }
+};
+
+}  // namespace
+
+template <typename T>
+struct ViewProperty {
+  T default_value;
+  const char* name;
+  View::PropertyDeallocator deallocator;
+};
+
+template <typename T>
+void View::SetLocalProperty(const ViewProperty<T>* property, T value) {
+  int64 old = SetLocalPropertyInternal(
+      property, property->name,
+      value == property->default_value ? nullptr : property->deallocator,
+      ViewPropertyCaster<T>::ToInt64(value),
+      ViewPropertyCaster<T>::ToInt64(property->default_value));
+  if (property->deallocator &&
+      old != ViewPropertyCaster<T>::ToInt64(property->default_value)) {
+    (*property->deallocator)(old);
+  }
+}
+
+template <typename T>
+T View::GetLocalProperty(const ViewProperty<T>* property) const {
+  return ViewPropertyCaster<T>::FromInt64(GetLocalPropertyInternal(
+      property, ViewPropertyCaster<T>::ToInt64(property->default_value)));
+}
+
+template <typename T>
+void View::ClearLocalProperty(const ViewProperty<T>* property) {
+  SetLocalProperty(property, property->default_value);
+}
+
+}  // namespace mojo
+
+// Macros to instantiate the property getter/setter template functions.
+#define DECLARE_EXPORTED_VIEW_PROPERTY_TYPE(EXPORT, T)                         \
+  template EXPORT void mojo::View::SetLocalProperty(                           \
+      const mojo::ViewProperty<T>*, T);                                        \
+  template EXPORT T mojo::View::GetLocalProperty(const mojo::ViewProperty<T>*) \
+      const;                                                                   \
+  template EXPORT void mojo::View::ClearLocalProperty(                         \
+      const mojo::ViewProperty<T>*);
+#define DECLARE_VIEW_PROPERTY_TYPE(T) DECLARE_EXPORTED_VIEW_PROPERTY_TYPE(, T)
+
+#define DEFINE_VIEW_PROPERTY_KEY(TYPE, NAME, DEFAULT)                      \
+  COMPILE_ASSERT(sizeof(TYPE) <= sizeof(int64), property_type_too_large);  \
+  namespace {                                                              \
+  const mojo::ViewProperty<TYPE> NAME##_Value = {DEFAULT, #NAME, nullptr}; \
+  }                                                                        \
+  const mojo::ViewProperty<TYPE>* const NAME = &NAME##_Value;
+
+#define DEFINE_LOCAL_VIEW_PROPERTY_KEY(TYPE, NAME, DEFAULT)                \
+  COMPILE_ASSERT(sizeof(TYPE) <= sizeof(int64), property_type_too_large);  \
+  namespace {                                                              \
+  const mojo::ViewProperty<TYPE> NAME##_Value = {DEFAULT, #NAME, nullptr}; \
+  const mojo::ViewProperty<TYPE>* const NAME = &NAME##_Value;              \
+  }
+
+#define DEFINE_OWNED_VIEW_PROPERTY_KEY(TYPE, NAME, DEFAULT)            \
+  namespace {                                                          \
+  void Deallocator##NAME(int64 p) {                                    \
+    enum { type_must_be_complete = sizeof(TYPE) };                     \
+    delete mojo::ViewPropertyCaster<TYPE*>::FromInt64(p);              \
+  }                                                                    \
+  const mojo::ViewProperty<TYPE*> NAME##_Value = {DEFAULT,             \
+                                                  #NAME,               \
+                                                  &Deallocator##NAME}; \
+  }                                                                    \
+  const mojo::ViewProperty<TYPE*>* const NAME = &NAME##_Value;
+
+#endif  // MOJO_SERVICES_PUBLIC_CPP_VIEW_MANAGER_VIEW_PROPERTY_H_