dom/bindings/BindingDeclarations.h
author James Teh <jteh@mozilla.com>
Thu, 07 Mar 2019 18:10:13 +0000
changeset 520910 c26d4a8d43c4d0d6f6e13135b8f35924123fe99e
parent 516464 9f776274089a2e001b347eb6d92e99d3decba8d8
permissions -rw-r--r--
Bug 1527922: Ensure the Reload button is disabled when testing against blank tabs in the browser toolbar key nav tests. r=Gijs For a blank tab, the Reload button should be disabled. These tests depend on this. This seems to be true when setting the new tab page to blank in Firefox Options. However, when we open about:blank with BrowserTestUtils.withNewTab, this is unreliable. That is, sometimes the Reload button is enabled, sometimes it isn't. I don't understand why this happens. For the purposes of these tests, just force the Reload button to be disabled for new, blank tabs so we get consistent results. Differential Revision: https://phabricator.services.mozilla.com/D22449

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

/**
 * A header for declaring various things that binding implementation headers
 * might need.  The idea is to make binding implementation headers safe to
 * include anywhere without running into include hell like we do with
 * BindingUtils.h
 */
#ifndef mozilla_dom_BindingDeclarations_h__
#define mozilla_dom_BindingDeclarations_h__

#include "js/RootingAPI.h"
#include "js/Value.h"

#include "mozilla/Maybe.h"
#include "mozilla/RootedOwningNonNull.h"
#include "mozilla/RootedRefPtr.h"

#include "mozilla/dom/DOMString.h"

#include "nsCOMPtr.h"
#include "nsString.h"
#include "nsTArray.h"

class nsIPrincipal;
class nsWrapperCache;

namespace mozilla {
namespace dom {

// Struct that serves as a base class for all dictionaries.  Particularly useful
// so we can use IsBaseOf to detect dictionary template arguments.
struct DictionaryBase {
 protected:
  bool ParseJSON(JSContext* aCx, const nsAString& aJSON,
                 JS::MutableHandle<JS::Value> aVal);

  bool StringifyToJSON(JSContext* aCx, JS::Handle<JSObject*> aObj,
                       nsAString& aJSON) const;

  // Struct used as a way to force a dictionary constructor to not init the
  // dictionary (via constructing from a pointer to this class).  We're putting
  // it here so that all the dictionaries will have access to it, but outside
  // code will not.
  struct FastDictionaryInitializer {};

  bool mIsAnyMemberPresent = false;

 private:
  // aString is expected to actually be an nsAString*.  Should only be
  // called from StringifyToJSON.
  static bool AppendJSONToString(const char16_t* aJSONData,
                                 uint32_t aDataLength, void* aString);

 public:
  bool IsAnyMemberPresent() const { return mIsAnyMemberPresent; }
};

template <typename T>
inline typename EnableIf<IsBaseOf<DictionaryBase, T>::value, void>::Type
ImplCycleCollectionUnlink(T& aDictionary) {
  aDictionary.UnlinkForCC();
}

template <typename T>
inline typename EnableIf<IsBaseOf<DictionaryBase, T>::value, void>::Type
ImplCycleCollectionTraverse(nsCycleCollectionTraversalCallback& aCallback,
                            T& aDictionary, const char* aName,
                            uint32_t aFlags = 0) {
  aDictionary.TraverseForCC(aCallback, aFlags);
}

// Struct that serves as a base class for all typed arrays and array buffers and
// array buffer views.  Particularly useful so we can use IsBaseOf to detect
// typed array/buffer/view template arguments.
struct AllTypedArraysBase {};

// Struct that serves as a base class for all owning unions.
// Particularly useful so we can use IsBaseOf to detect owning union
// template arguments.
struct AllOwningUnionBase {};

struct EnumEntry {
  const char* value;
  size_t length;
};

enum class CallerType : uint32_t;

class MOZ_STACK_CLASS GlobalObject {
 public:
  GlobalObject(JSContext* aCx, JSObject* aObject);

  JSObject* Get() const { return mGlobalJSObject; }

  nsISupports* GetAsSupports() const;

  // The context that this returns is not guaranteed to be in the compartment of
  // the object returned from Get(), in fact it's generally in the caller's
  // compartment.
  JSContext* Context() const { return mCx; }

  bool Failed() const { return !Get(); }

  // It returns the subjectPrincipal if called on the main-thread, otherwise
  // a nullptr is returned.
  nsIPrincipal* GetSubjectPrincipal() const;

  // Get the caller type.  Note that this needs to be called before anyone has
  // had a chance to mess with the JSContext.
  dom::CallerType CallerType() const;

 protected:
  JS::Rooted<JSObject*> mGlobalJSObject;
  JSContext* mCx;
  mutable nsISupports* MOZ_UNSAFE_REF(
      "Valid because GlobalObject is a stack "
      "class, and mGlobalObject points to the "
      "global, so it won't be destroyed as long "
      "as GlobalObject lives on the stack") mGlobalObject;
};

// Class for representing optional arguments.
template <typename T, typename InternalType>
class Optional_base {
 public:
  Optional_base() {}

  explicit Optional_base(const T& aValue) { mImpl.emplace(aValue); }

  bool operator==(const Optional_base<T, InternalType>& aOther) const {
    return mImpl == aOther.mImpl;
  }

  bool operator!=(const Optional_base<T, InternalType>& aOther) const {
    return mImpl != aOther.mImpl;
  }

  template <typename T1, typename T2>
  explicit Optional_base(const T1& aValue1, const T2& aValue2) {
    mImpl.emplace(aValue1, aValue2);
  }

  bool WasPassed() const { return mImpl.isSome(); }

  // Return InternalType here so we can work with it usefully.
  template <typename... Args>
  InternalType& Construct(Args&&... aArgs) {
    mImpl.emplace(std::forward<Args>(aArgs)...);
    return *mImpl;
  }

  void Reset() { mImpl.reset(); }

  const T& Value() const { return *mImpl; }

  // Return InternalType here so we can work with it usefully.
  InternalType& Value() { return *mImpl; }

  // And an explicit way to get the InternalType even if we're const.
  const InternalType& InternalValue() const { return *mImpl; }

  // If we ever decide to add conversion operators for optional arrays
  // like the ones Nullable has, we'll need to ensure that Maybe<> has
  // the boolean before the actual data.

 private:
  // Forbid copy-construction and assignment
  Optional_base(const Optional_base& other) = delete;
  const Optional_base& operator=(const Optional_base& other) = delete;

 protected:
  Maybe<InternalType> mImpl;
};

template <typename T>
class Optional : public Optional_base<T, T> {
 public:
  MOZ_ALLOW_TEMPORARY Optional() : Optional_base<T, T>() {}

  explicit Optional(const T& aValue) : Optional_base<T, T>(aValue) {}
};

template <typename T>
class Optional<JS::Handle<T> >
    : public Optional_base<JS::Handle<T>, JS::Rooted<T> > {
 public:
  MOZ_ALLOW_TEMPORARY Optional()
      : Optional_base<JS::Handle<T>, JS::Rooted<T> >() {}

  explicit Optional(JSContext* cx)
      : Optional_base<JS::Handle<T>, JS::Rooted<T> >() {
    this->Construct(cx);
  }

  Optional(JSContext* cx, const T& aValue)
      : Optional_base<JS::Handle<T>, JS::Rooted<T> >(cx, aValue) {}

  // Override the const Value() to return the right thing so we're not
  // returning references to temporaries.
  JS::Handle<T> Value() const { return *this->mImpl; }

  // And we have to override the non-const one too, since we're
  // shadowing the one on the superclass.
  JS::Rooted<T>& Value() { return *this->mImpl; }
};

// A specialization of Optional for JSObject* to make sure that when someone
// calls Construct() on it we will pre-initialized the JSObject* to nullptr so
// it can be traced safely.
template <>
class Optional<JSObject*> : public Optional_base<JSObject*, JSObject*> {
 public:
  Optional() : Optional_base<JSObject*, JSObject*>() {}

  explicit Optional(JSObject* aValue)
      : Optional_base<JSObject*, JSObject*>(aValue) {}

  // Don't allow us to have an uninitialized JSObject*
  JSObject*& Construct() {
    // The Android compiler sucks and thinks we're trying to construct
    // a JSObject* from an int if we don't cast here.  :(
    return Optional_base<JSObject*, JSObject*>::Construct(
        static_cast<JSObject*>(nullptr));
  }

  template <class T1>
  JSObject*& Construct(const T1& t1) {
    return Optional_base<JSObject*, JSObject*>::Construct(t1);
  }
};

// A specialization of Optional for JS::Value to make sure no one ever uses it.
template <>
class Optional<JS::Value> {
 private:
  Optional() = delete;

  explicit Optional(const JS::Value& aValue) = delete;
};

// A specialization of Optional for NonNull that lets us get a T& from Value()
template <typename U>
class NonNull;
template <typename T>
class Optional<NonNull<T> > : public Optional_base<T, NonNull<T> > {
 public:
  // We want our Value to actually return a non-const reference, even
  // if we're const.  At least for things that are normally pointer
  // types...
  T& Value() const { return *this->mImpl->get(); }

  // And we have to override the non-const one too, since we're
  // shadowing the one on the superclass.
  NonNull<T>& Value() { return *this->mImpl; }
};

// A specialization of Optional for OwningNonNull that lets us get a
// T& from Value()
template <typename T>
class Optional<OwningNonNull<T> > : public Optional_base<T, OwningNonNull<T> > {
 public:
  // We want our Value to actually return a non-const reference, even
  // if we're const.  At least for things that are normally pointer
  // types...
  T& Value() const { return *this->mImpl->get(); }

  // And we have to override the non-const one too, since we're
  // shadowing the one on the superclass.
  OwningNonNull<T>& Value() { return *this->mImpl; }
};

// Specialization for strings.
// XXXbz we can't pull in FakeString here, because it depends on internal
// strings.  So we just have to forward-declare it and reimplement its
// ToAStringPtr.

namespace binding_detail {
struct FakeString;
}  // namespace binding_detail

template <>
class Optional<nsAString> {
 public:
  Optional() : mStr(nullptr) {}

  bool WasPassed() const { return !!mStr; }

  void operator=(const nsAString* str) {
    MOZ_ASSERT(str);
    mStr = str;
  }

  // If this code ever goes away, remove the comment pointing to it in the
  // FakeString class in BindingUtils.h.
  void operator=(const binding_detail::FakeString* str) {
    MOZ_ASSERT(str);
    mStr = reinterpret_cast<const nsString*>(str);
  }

  const nsAString& Value() const {
    MOZ_ASSERT(WasPassed());
    return *mStr;
  }

 private:
  // Forbid copy-construction and assignment
  Optional(const Optional& other) = delete;
  const Optional& operator=(const Optional& other) = delete;

  const nsAString* mStr;
};

template <typename T>
inline void ImplCycleCollectionUnlink(Optional<T>& aField) {
  if (aField.WasPassed()) {
    ImplCycleCollectionUnlink(aField.Value());
  }
}

template <typename T>
inline void ImplCycleCollectionTraverse(
    nsCycleCollectionTraversalCallback& aCallback, Optional<T>& aField,
    const char* aName, uint32_t aFlags = 0) {
  if (aField.WasPassed()) {
    ImplCycleCollectionTraverse(aCallback, aField.Value(), aName, aFlags);
  }
}

template <class T>
class NonNull {
 public:
  NonNull()
#ifdef DEBUG
      : inited(false)
#endif
  {
  }

  // This is no worse than get() in terms of const handling.
  operator T&() const {
    MOZ_ASSERT(inited);
    MOZ_ASSERT(ptr, "NonNull<T> was set to null");
    return *ptr;
  }

  operator T*() const {
    MOZ_ASSERT(inited);
    MOZ_ASSERT(ptr, "NonNull<T> was set to null");
    return ptr;
  }

  void operator=(T* t) {
    ptr = t;
    MOZ_ASSERT(ptr);
#ifdef DEBUG
    inited = true;
#endif
  }

  template <typename U>
  void operator=(U* t) {
    ptr = t->ToAStringPtr();
    MOZ_ASSERT(ptr);
#ifdef DEBUG
    inited = true;
#endif
  }

  T** Slot() {
#ifdef DEBUG
    inited = true;
#endif
    return &ptr;
  }

  T* Ptr() {
    MOZ_ASSERT(inited);
    MOZ_ASSERT(ptr, "NonNull<T> was set to null");
    return ptr;
  }

  // Make us work with smart-ptr helpers that expect a get()
  T* get() const {
    MOZ_ASSERT(inited);
    MOZ_ASSERT(ptr);
    return ptr;
  }

 protected:
  // ptr is left uninitialized for optimization purposes.
  MOZ_INIT_OUTSIDE_CTOR T* ptr;
#ifdef DEBUG
  bool inited;
#endif
};

// Class for representing sequences in arguments.  We use a non-auto array
// because that allows us to use sequences of sequences and the like.  This
// needs to be fallible because web content controls the length of the array,
// and can easily try to create very large lengths.
template <typename T>
class Sequence : public FallibleTArray<T> {
 public:
  Sequence() : FallibleTArray<T>() {}
};

inline nsWrapperCache* GetWrapperCache(nsWrapperCache* cache) { return cache; }

inline nsWrapperCache* GetWrapperCache(void* p) { return nullptr; }

// Helper template for smart pointers to resolve ambiguity between
// GetWrappeCache(void*) and GetWrapperCache(const ParentObject&).
template <template <typename> class SmartPtr, typename T>
inline nsWrapperCache* GetWrapperCache(const SmartPtr<T>& aObject) {
  return GetWrapperCache(aObject.get());
}

enum class ReflectionScope { Content, NAC, UAWidget };

struct MOZ_STACK_CLASS ParentObject {
  template <class T>
  MOZ_IMPLICIT ParentObject(T* aObject)
      : mObject(ToSupports(aObject)),
        mWrapperCache(GetWrapperCache(aObject)),
        mReflectionScope(ReflectionScope::Content) {}

  template <class T, template <typename> class SmartPtr>
  MOZ_IMPLICIT ParentObject(const SmartPtr<T>& aObject)
      : mObject(aObject.get()),
        mWrapperCache(GetWrapperCache(aObject.get())),
        mReflectionScope(ReflectionScope::Content) {}

  ParentObject(nsISupports* aObject, nsWrapperCache* aCache)
      : mObject(aObject),
        mWrapperCache(aCache),
        mReflectionScope(ReflectionScope::Content) {}

  // We don't want to make this an nsCOMPtr because of performance reasons, but
  // it's safe because ParentObject is a stack class.
  nsISupports* const MOZ_NON_OWNING_REF mObject;
  nsWrapperCache* const mWrapperCache;
  ReflectionScope mReflectionScope;
};

namespace binding_detail {

// Class for simple sequence arguments, only used internally by codegen.
template <typename T>
class AutoSequence : public AutoTArray<T, 16> {
 public:
  AutoSequence() : AutoTArray<T, 16>() {}

  // Allow converting to const sequences as needed
  operator const Sequence<T>&() const {
    return *reinterpret_cast<const Sequence<T>*>(this);
  }
};

}  // namespace binding_detail

// Enum to represent a system or non-system caller type.
enum class CallerType : uint32_t { System, NonSystem };

// A class that can be passed (by value or const reference) to indicate that the
// caller is always a system caller.  This can be used as the type of an
// argument to force only system callers to call a function.
class SystemCallerGuarantee {
 public:
  operator CallerType() const { return CallerType::System; }
};

class ProtoAndIfaceCache;
typedef void (*CreateInterfaceObjectsMethod)(JSContext* aCx,
                                             JS::Handle<JSObject*> aGlobal,
                                             ProtoAndIfaceCache& aCache,
                                             bool aDefineOnGlobal);
JS::Handle<JSObject*> GetPerInterfaceObjectHandle(
    JSContext* aCx, size_t aSlotId, CreateInterfaceObjectsMethod aCreator,
    bool aDefineOnGlobal);

}  // namespace dom
}  // namespace mozilla

#endif  // mozilla_dom_BindingDeclarations_h__