lazyContainerDataSource.h

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//
// Copyright 2022 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.
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#ifndef PXR_IMAGING_HD_LAZY_CONTAINER_DATA_SOURCE_H
#define PXR_IMAGING_HD_LAZY_CONTAINER_DATA_SOURCE_H

#include "pxr/imaging/hd/dataSource.h"

PXR_NAMESPACE_OPEN_SCOPE

/// \class HdLazyContainerDataSource
///
/// A container data source lazily evaluating the given thunk to
/// forward all calls to the container data source computed by the thunk.
///
class HdLazyContainerDataSource : public HdContainerDataSource
{
public:
    HD_DECLARE_DATASOURCE(HdLazyContainerDataSource);

    using Thunk = std::function<HdContainerDataSourceHandle()>;

    HD_API
    TfTokenVector GetNames() override;
    HD_API
    HdDataSourceBaseHandle Get(const TfToken &name) override;

    HD_API
    ~HdLazyContainerDataSource();

protected:
    HD_API
    HdLazyContainerDataSource(const Thunk &thunk);

private:
    HdContainerDataSourceHandle _GetSrc();

    Thunk _thunk;
    HdContainerDataSourceAtomicHandle _src;
};

PXR_NAMESPACE_CLOSE_SCOPE

#endif