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/* -*- 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
#ifndef nsQueryFrame_h
#define nsQueryFrame_h
#include <type_traits>
#include "nscore.h"
#include "mozilla/Assertions.h"
namespace mozilla {
class ScrollContainerFrame;
}
#define NS_DECL_QUERYFRAME_TARGET(classname) \
static const nsQueryFrame::FrameIID kFrameIID = \
nsQueryFrame::classname##_id; \
typedef classname Has_NS_DECL_QUERYFRAME_TARGET;
#define NS_DECL_QUERYFRAME void* QueryFrame(FrameIID id) const override;
#define NS_QUERYFRAME_HEAD(class) \
void* class ::QueryFrame(FrameIID id) const { \
switch (id) {
#define NS_QUERYFRAME_ENTRY(class) \
case class ::kFrameIID: { \
static_assert( \
std::is_same_v<class, class ::Has_NS_DECL_QUERYFRAME_TARGET>, \
#class " must declare itself as a queryframe target"); \
return const_cast<class*>(static_cast<const class*>(this)); \
}
#define NS_QUERYFRAME_ENTRY_CONDITIONAL(class, condition) \
case class ::kFrameIID: \
if (condition) { \
static_assert( \
std::is_same_v<class, class ::Has_NS_DECL_QUERYFRAME_TARGET>, \
#class " must declare itself as a queryframe target"); \
return const_cast<class*>(static_cast<const class*>(this)); \
} \
break;
#define NS_QUERYFRAME_TAIL_INHERITING(class) \
default: \
break; \
} \
return class ::QueryFrame(id); \
}
#define NS_QUERYFRAME_TAIL_INHERITANCE_ROOT \
default: \
break; \
} \
MOZ_ASSERT(id != GetFrameId(), \
"A frame failed to QueryFrame to its *own type*. " \
"It may be missing NS_DECL_QUERYFRAME, or a " \
"NS_QUERYFRAME_ENTRY() line with its own type name"); \
return nullptr; \
}
class nsQueryFrame {
public:
enum FrameIID {
#define FRAME_ID(classname, ...) classname##_id,
#define ABSTRACT_FRAME_ID(classname) classname##_id,
#include "mozilla/FrameIdList.h"
#undef FRAME_ID
#undef ABSTRACT_FRAME_ID
};
// A strict subset of FrameIID above for frame classes that we instantiate.
enum class ClassID : uint8_t {
#define FRAME_ID(classname, ...) classname##_id,
#define ABSTRACT_FRAME_ID(classname)
#include "mozilla/FrameIdList.h"
#undef FRAME_ID
#undef ABSTRACT_FRAME_ID
};
virtual void* QueryFrame(FrameIID id) const = 0;
};
class nsIFrame;
namespace detail {
template <typename Dest, typename = void>
struct FastQueryFrame {
static constexpr bool kSupported = false;
};
// For final classes we can check the class id.
template <typename Dest>
struct FastQueryFrame<Dest, std::enable_if_t<std::is_final_v<Dest>, void>> {
static constexpr bool kSupported = true;
template <typename Src>
static Dest* QueryFrame(Src* aPtr) {
return nsQueryFrame::FrameIID(aPtr->GetClassID()) == Dest::kFrameIID
? static_cast<Dest*>(aPtr)
: nullptr;
}
};
#define IMPL_FAST_QUERYFRAME(Dest_, Check_) \
template <> \
struct FastQueryFrame<Dest_, void> { \
static constexpr bool kSupported = true; \
template <typename Src> \
static Dest_* QueryFrame(Src* aPtr) { \
return aPtr->Check_() ? static_cast<Dest_*>(aPtr) : nullptr; \
} \
}
IMPL_FAST_QUERYFRAME(mozilla::ScrollContainerFrame,
IsScrollContainerOrSubclass);
#undef IMPL_FAST_QUERYFRAME
}
template <typename Source>
class do_QueryFrameHelper {
public:
explicit do_QueryFrameHelper(Source* s) : mRawPtr(s) {}
// The return and argument types here are arbitrarily selected so no
// corresponding member function exists.
using MatchNullptr = void (*)(double, float);
// Implicit constructor for nullptr, trick borrowed from already_AddRefed.
MOZ_IMPLICIT do_QueryFrameHelper(MatchNullptr aRawPtr) : mRawPtr(nullptr) {}
template <typename Dest>
operator Dest*() {
static_assert(std::is_same_v<std::remove_const_t<Dest>,
typename Dest::Has_NS_DECL_QUERYFRAME_TARGET>,
"Dest must declare itself as a queryframe target");
if (!mRawPtr) {
return nullptr;
}
if constexpr (::detail::FastQueryFrame<Dest>::kSupported) {
static_assert(
std::is_base_of_v<nsIFrame, Source>,
"We only support fast do_QueryFrame() where the source must be a "
"derived class of nsIFrame. Consider a two-step do_QueryFrame() "
"(once to nsIFrame, another to the target) if absolutely needed.");
Dest* f = ::detail::FastQueryFrame<Dest>::QueryFrame(mRawPtr);
MOZ_ASSERT(
f == reinterpret_cast<Dest*>(mRawPtr->QueryFrame(Dest::kFrameIID)),
"fast and slow paths should give the same result");
return f;
}
if constexpr (std::is_base_of_v<nsIFrame, Source> &&
std::is_base_of_v<nsIFrame, Dest>) {
// For non-final frames we can still optimize the virtual call some of the
// time.
if (nsQueryFrame::FrameIID(mRawPtr->GetClassID()) == Dest::kFrameIID) {
auto* f = static_cast<Dest*>(mRawPtr);
MOZ_ASSERT(
f == reinterpret_cast<Dest*>(mRawPtr->QueryFrame(Dest::kFrameIID)),
"fast and slow paths should give the same result");
return f;
}
}
return reinterpret_cast<Dest*>(mRawPtr->QueryFrame(Dest::kFrameIID));
}
private:
Source* mRawPtr;
};
template <typename T>
inline do_QueryFrameHelper<T> do_QueryFrame(T* s) {
return do_QueryFrameHelper<T>(s);
}
#endif // nsQueryFrame_h