sceneIndex.h

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

#include "pxr/pxr.h"

#include <set>
#include <unordered_map>

#include "pxr/base/tf/declarePtrs.h"
#include "pxr/base/tf/singleton.h"
#include "pxr/base/tf/denseHashSet.h"


#include "pxr/usd/sdf/path.h"

#include "pxr/imaging/hd/api.h"
#include "pxr/imaging/hd/dataSource.h"
#include "pxr/imaging/hd/dataSourceLocator.h"
#include "pxr/imaging/hd/sceneIndexObserver.h"

PXR_NAMESPACE_OPEN_SCOPE

TF_DECLARE_WEAK_AND_REF_PTRS(HdSceneIndexBase);

struct HdSceneIndexPrim
{
    TfToken primType;
    HdContainerDataSourceHandle dataSource;

    bool IsDefined() const { return bool(dataSource); }
    explicit operator bool() const { return IsDefined(); }
};

class HdSceneIndexBase : public TfRefBase, public TfWeakBase
{
public:
    HD_API
    HdSceneIndexBase();

    HD_API
    ~HdSceneIndexBase() override;

    // ------------------------------------------------------------------------
    // Scene Observer API
    // ------------------------------------------------------------------------

    HD_API
    void AddObserver(const HdSceneIndexObserverPtr &observer);

    HD_API
    void RemoveObserver(const HdSceneIndexObserverPtr &observer);

    // ------------------------------------------------------------------------
    // Scene Data API
    // ------------------------------------------------------------------------

    virtual HdSceneIndexPrim GetPrim(const SdfPath &primPath) const = 0;

    virtual SdfPathVector GetChildPrimPaths(const SdfPath &primPath) const = 0;

    HdDataSourceBaseHandle GetDataSource(
            const SdfPath &primPath,
            const HdDataSourceLocator &locator) const
    {
        return HdContainerDataSource::Get(
                GetPrim(primPath).dataSource, locator);
    }

    // ------------------------------------------------------------------------
    // System-wide API
    // ------------------------------------------------------------------------

    HD_API
    void SystemMessage(
        const TfToken &messageType,
        const HdDataSourceBaseHandle &args);

    // ------------------------------------------------------------------------
    // User Interface Utilities
    // ------------------------------------------------------------------------

    HD_API
    std::string GetDisplayName() const;

    HD_API
    void SetDisplayName(const std::string &n);

    HD_API
    void AddTag(const TfToken &tag);

    HD_API
    void RemoveTag(const TfToken &tag);

    HD_API
    bool HasTag(const TfToken &tag) const;

    HD_API
    TfTokenVector GetTags() const;

protected:

    HD_API
    void _SendPrimsAdded(
        const HdSceneIndexObserver::AddedPrimEntries &entries);

    HD_API
    void _SendPrimsRemoved(
        const HdSceneIndexObserver::RemovedPrimEntries &entries);

    HD_API
    void _SendPrimsDirtied(
        const HdSceneIndexObserver::DirtiedPrimEntries &entries);


    HD_API
    void _SendPrimsRenamed(
        const HdSceneIndexObserver::RenamedPrimEntries &entries);


    HD_API
    bool _IsObserved() const;

    HD_API
    virtual void _SystemMessage(
        const TfToken &messageType,
        const HdDataSourceBaseHandle &args);

private:
    void _RemoveExpiredObservers();

    // Scoped (RAII) helper to manage tracking recursion depth,
    // and to remove expired observers after completing delivery.
    struct _NotifyScope;

    // Registered observers, in order of registration.
    using _Observers = std::vector<HdSceneIndexObserverPtr>;
    _Observers _observers;

    // Count of in-flight observer notifications
    int _notifyDepth;

    // Flag hinting that expired observers may exist.
    bool _shouldRemoveExpiredObservers;

    // User-visible label for this scene index
    std::string _displayName;

    // Tags used to categorize this scene index
    using _TagSet = TfDenseHashSet<TfToken, TfHash, std::equal_to<TfToken>, 8>;
    _TagSet _tags;
};


class HdSceneIndexNameRegistry
    : public TfSingleton<HdSceneIndexNameRegistry> 
{
    friend class TfSingleton<HdSceneIndexNameRegistry>;

    HdSceneIndexNameRegistry() = default;

public:

    HD_API
    static HdSceneIndexNameRegistry &GetInstance()  {
        return TfSingleton<HdSceneIndexNameRegistry>::GetInstance();
    }

    HD_API
    void RegisterNamedSceneIndex(
        const std::string &name, HdSceneIndexBasePtr instance);

    HD_API
    std::vector<std::string> GetRegisteredNames();

    HD_API
    HdSceneIndexBaseRefPtr GetNamedSceneIndex(const std::string &name);

private:

    using _NamedInstanceMap =
        std::unordered_map<std::string, HdSceneIndexBasePtr>;

    _NamedInstanceMap _namedInstances;
};

PXR_NAMESPACE_CLOSE_SCOPE

#endif // PXR_IMAGING_HD_SCENE_INDEX_H