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accessorHelpers.h
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accessorHelpers.h
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//
// Copyright 2016 Pixar
//
// Licensed under the Apache License, Version 2.0 (the "Apache License")
// with the following modification; you may not use this file except in
// compliance with the Apache License and the following modification to it:
// Section 6. Trademarks. is deleted and replaced with:
//
// 6. Trademarks. This License does not grant permission to use the trade
// names, trademarks, service marks, or product names of the Licensor
// and its affiliates, except as required to comply with Section 4(c) of
// the License and to reproduce the content of the NOTICE file.
//
// You may obtain a copy of the Apache License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the Apache License with the above modification is
// distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the Apache License for the specific
// language governing permissions and limitations under the Apache License.
//
#ifndef PXR_USD_SDF_ACCESSOR_HELPERS_H
#define PXR_USD_SDF_ACCESSOR_HELPERS_H
/// \file sdf/accessorHelpers.h
#include "pxr/pxr.h"
#include "pxr/usd/sdf/schema.h"
#include "pxr/usd/sdf/spec.h"
#include "pxr/usd/sdf/types.h"
#include <type_traits>
// This file defines macros intended to reduce the amount of boilerplate code
// associated with adding new metadata to SdfSpec subclasses. There's still a
// lot of files to touch, but these at least reduce the copy/paste/edit load.
//
// Prior to using these macros in the SdfSpec implementation file, define the
// following symbols:
//
// #define SDF_ACCESSOR_CLASS SdfSomeSpec
// #define SDF_ACCESSOR_READ_PREDICATE(key_) _CanRead(key_)
// #define SDF_ACCESSOR_WRITE_PREDICATE(key_) _CanWrite(key_)
//
// ...where _CanRead and _CanWrite are member functions of the specified class,
// with the signature 'bool _fn_(const TfToken&)'. If either accessor predicate
// is unnecessary, #define the corresponding symbol to 'SDF_NO_PREDICATE'.
//
// Also, please observe good form and #undef the symbols after instancing the
// accessor macros.
PXR_NAMESPACE_OPEN_SCOPE
// "Helper" macros
#define _GET_KEY_(key_) key_
#define SDF_NO_PREDICATE true
#define _GET_WITH_FALLBACK(key_, heldType_) \
{ \
typedef Sdf_AccessorHelpers<SDF_ACCESSOR_CLASS> _Helper; \
const VtValue& value = _Helper::GetField(this, key_); \
if (value.IsEmpty() || !value.IsHolding<heldType_>()) { \
const SdfSchemaBase& schema = _Helper::GetSchema(this); \
return schema.GetFallback(_GET_KEY_(key_)).Get<heldType_>(); \
} \
else { \
return value.Get<heldType_>(); \
} \
}
// Accessor methods for "simple type" values: Get, Is, Set, Has, Clear
// Usually the client will utilize one of the combination macros (below).
#define SDF_DEFINE_GET(name_, key_, heldType_) \
heldType_ \
SDF_ACCESSOR_CLASS::Get ## name_() const \
{ \
if (SDF_ACCESSOR_READ_PREDICATE(_GET_KEY_(key_))) { \
/* Empty clause needed to prevent compiler complaints */ \
} \
\
_GET_WITH_FALLBACK(key_, heldType_); \
}
#define SDF_DEFINE_IS(name_, key_) \
bool \
SDF_ACCESSOR_CLASS::Is ## name_() const \
{ \
if (!SDF_ACCESSOR_READ_PREDICATE(_GET_KEY_(key_))) { \
return false; \
} \
\
_GET_WITH_FALLBACK(key_, bool); \
}
#define SDF_DEFINE_SET(name_, key_, argType_) \
void \
SDF_ACCESSOR_CLASS::Set ## name_(argType_ value) \
{ \
if (SDF_ACCESSOR_WRITE_PREDICATE(_GET_KEY_(key_))) { \
typedef Sdf_AccessorHelpers<SDF_ACCESSOR_CLASS> _Helper; \
_Helper::SetField(this, _GET_KEY_(key_), value); \
} \
}
#define SDF_DEFINE_HAS(name_, key_) \
bool \
SDF_ACCESSOR_CLASS::Has ## name_() const \
{ \
typedef Sdf_AccessorHelpers<SDF_ACCESSOR_CLASS> _Helper; \
return SDF_ACCESSOR_READ_PREDICATE(_GET_KEY_(key_)) ? \
_Helper::HasField(this, _GET_KEY_(key_)) : false; \
}
#define SDF_DEFINE_CLEAR(name_, key_) \
void \
SDF_ACCESSOR_CLASS::Clear ## name_() \
{ \
typedef Sdf_AccessorHelpers<SDF_ACCESSOR_CLASS> _Helper; \
if (SDF_ACCESSOR_WRITE_PREDICATE(_GET_KEY_(key_))) { \
_Helper::ClearField(this, _GET_KEY_(key_)); \
} \
}
// Accessor methods similar to the above, but intended for private use in
// the SdSpec classes.
#define SDF_DEFINE_GET_PRIVATE(name_, key_, heldType_) \
heldType_ \
SDF_ACCESSOR_CLASS::_Get ## name_() const \
{ \
if (SDF_ACCESSOR_READ_PREDICATE(_GET_KEY_(key_))) { \
/* Empty clause needed to prevent compiler complaints */ \
} \
\
_GET_WITH_FALLBACK(key_, heldType_); \
}
// Accessor methods for VtDictionary types, utilizing SdDictionaryProxy for the
// 'Get' accessors. Due to unusual naming in the original SdSpec API, these
// macros accept/require explicit accessor method names. Dammit.
#define SDF_DEFINE_DICTIONARY_GET(name_, key_) \
SdfDictionaryProxy \
SDF_ACCESSOR_CLASS::name_() const \
{ \
typedef Sdf_AccessorHelpers<SDF_ACCESSOR_CLASS> _Helper; \
return SDF_ACCESSOR_READ_PREDICATE(_GET_KEY_(key_)) ? \
SdfDictionaryProxy(_Helper::GetSpecHandle(this), _GET_KEY_(key_)) : \
SdfDictionaryProxy(); \
}
#define SDF_DEFINE_DICTIONARY_SET(name_, key_) \
void \
SDF_ACCESSOR_CLASS::name_( \
const std::string& name, \
const VtValue& value) \
{ \
typedef Sdf_AccessorHelpers<SDF_ACCESSOR_CLASS> _Helper; \
if (SDF_ACCESSOR_WRITE_PREDICATE(_GET_KEY_(key_))) { \
SdfDictionaryProxy proxy( \
_Helper::GetSpecHandle(this), _GET_KEY_(key_)); \
if (value.IsEmpty()) { \
proxy.erase(name); \
} \
else { \
proxy[name] = value; \
} \
} \
}
// Convenience macros to provide common combinations of value accessors
// Convert non-trivial types like `std::string` to `const std::string&` while
// preserving the type for `int`, `bool`, `char`, etc.
template <typename T>
using Sdf_SetParameter = std::conditional<
std::is_arithmetic<T>::value, std::add_const_t<T>,
std::add_lvalue_reference_t<std::add_const_t<T>>>;
#define SDF_DEFINE_TYPED_GET_SET(name_, key_, getType_, setType_) \
SDF_DEFINE_GET(name_, key_, getType_) \
SDF_DEFINE_SET(name_, key_, setType_)
#define SDF_DEFINE_TYPED_GET_SET_HAS_CLEAR(name_, key_, getType_, setType_) \
SDF_DEFINE_TYPED_GET_SET(name_, key_, getType_, setType_) \
SDF_DEFINE_HAS(name_, key_) \
SDF_DEFINE_CLEAR(name_, key_)
#define SDF_DEFINE_GET_SET(name_, key_, type_) \
SDF_DEFINE_TYPED_GET_SET(name_, key_, type_, \
Sdf_SetParameter<type_>::type)
#define SDF_DEFINE_GET_SET_HAS_CLEAR(name_, key_, type_) \
SDF_DEFINE_TYPED_GET_SET_HAS_CLEAR(name_, key_, type_, \
Sdf_SetParameter<type_>::type)
#define SDF_DEFINE_IS_SET(name_, key_) \
SDF_DEFINE_IS(name_, key_) \
SDF_DEFINE_SET(name_, key_, bool)
#define SDF_DEFINE_DICTIONARY_GET_SET(getName_, setName_, key_) \
SDF_DEFINE_DICTIONARY_GET(getName_, key_) \
SDF_DEFINE_DICTIONARY_SET(setName_, key_)
// Implementation details
// The helper macros above can be used in the implementation of a spec
// class or a spec API class (see declareSpec.h for details). Both cases
// access data in a different way -- spec classes can query their data
// members directly, while spec API classes need to query their associated
// spec. These templates capture those differences.
template <class T,
bool IsForSpec = std::is_base_of<SdfSpec, T>::value>
struct Sdf_AccessorHelpers;
template <class T>
struct Sdf_AccessorHelpers<T, true>
{
static const SdfSchemaBase& GetSchema(const T* spec)
{ return spec->GetSchema(); }
static VtValue GetField(const T* spec, const TfToken& key)
{ return spec->GetField(key); }
template <class V>
static bool SetField(T* spec, const TfToken& key, const V& value)
{ return spec->SetField(key, value); }
static bool HasField(const T* spec, const TfToken& key)
{ return spec->HasField(key); }
static void ClearField(T* spec, const TfToken& key)
{ spec->ClearField(key); }
static SdfSpecHandle GetSpecHandle(const T* spec)
{ return SdfCreateNonConstHandle(spec); }
};
template <class T>
struct Sdf_AccessorHelpers<T, false>
{
static const SdfSchemaBase& GetSchema(const T* spec)
{ return spec->_GetSpec().GetSchema(); }
static VtValue GetField(const T* spec, const TfToken& key)
{ return spec->_GetSpec().GetField(key); }
template <class V>
static bool SetField(T* spec, const TfToken& key, const V& value)
{ return spec->_GetSpec().SetField(key, value); }
static bool HasField(const T* spec, const TfToken& key)
{ return spec->_GetSpec().HasField(key); }
static void ClearField(T* spec, const TfToken& key)
{ spec->_GetSpec().ClearField(key); }
static SdfSpecHandle GetSpecHandle(const T* spec)
{ return SdfCreateNonConstHandle(&(spec->_GetSpec())); }
};
PXR_NAMESPACE_CLOSE_SCOPE
#endif // #ifndef PXR_USD_SDF_ACCESSOR_HELPERS_H