notice.h

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//
// Copyright 2021 Pixar
//
// Licensed under the terms set forth in the LICENSE.txt file available at
// https://openusd.org/license.
//
#ifndef PXR_USD_AR_NOTICE_H
#define PXR_USD_AR_NOTICE_H

#include "pxr/pxr.h"

#include "pxr/usd/ar/api.h"
#include "pxr/usd/ar/resolverContext.h"

#include "pxr/base/tf/notice.h"

#include <functional>

PXR_NAMESPACE_OPEN_SCOPE

template <class ContextObj>
bool Ar_ContextIsHolding(
    const ContextObj& contextObj, const ArResolverContext& ctx)
{
    const ContextObj* testObj = ctx.Get<ContextObj>();
    return testObj && *testObj == contextObj;
}

/// \class ArNotice
///
class ArNotice
{
public:
    /// \class ResolverNotice
    /// Base class for all ArResolver-related notices.
    class ResolverNotice
        : public TfNotice
    {
    public:
        AR_API virtual ~ResolverNotice();
    protected:
        AR_API ResolverNotice();
    };

    /// \class ResolverChanged
    /// Notice sent when asset paths may resolve to a different path than
    /// before due to a change in the resolver.
    class ResolverChanged 
        : public ResolverNotice
    {
    public:
        /// Create a notice indicating that the results of asset resolution
        /// might have changed, regardless of what ArResolverContext object
        /// is bound.
        AR_API
        ResolverChanged();

        /// Create a notice using \p affectsFn to determine the
        /// ArResolverContext objects that are affected by this resolver
        /// change. If \p affectsFn returns true, it means the results of asset
        /// resolution when the given ArResolverContext is bound might have
        /// changed.
        AR_API
        ResolverChanged(
            const std::function<bool(const ArResolverContext&)>& affectsFn);

        /// Create a notice indicating that the results of asset resolution when
        /// any ArResolverContext containing \p contextObj is bound might have
        /// changed.
        template <
            class ContextObj,
            typename std::enable_if<ArIsContextObject<ContextObj>::value>::type*
                = nullptr>
        ResolverChanged(
            const ContextObj& contextObj)
            // XXX: Ideally this would just use a lambda and forward it to
            // the other c'tor. Both of those cause issues in MSVC 2015; the
            // first causes an unspecified type error and the second causes
            // odd linker errors.
            : _affects(std::bind(&Ar_ContextIsHolding<ContextObj>, contextObj, 
                    std::placeholders::_1))
        {
        }
 
        AR_API
        virtual ~ResolverChanged();

        /// Returns true if the results of asset resolution when \p ctx
        /// is bound may be affected by this resolver change.
        AR_API 
        bool AffectsContext(const ArResolverContext& ctx) const;

    private:
        std::function<bool(const ArResolverContext&)> _affects;
    };

};

PXR_NAMESPACE_CLOSE_SCOPE

#endif