sceneIndexPluginRegistry.h

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//
// Copyright 2021 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_SCENE_INDEX_PLUGIN_REGISTRY_H
#define PXR_IMAGING_HD_SCENE_INDEX_PLUGIN_REGISTRY_H

#include "pxr/pxr.h"
#include "pxr/base/tf/singleton.h"
#include "pxr/base/tf/staticTokens.h"
#include "pxr/imaging/hf/pluginRegistry.h"
#include "pxr/imaging/hd/api.h"
#include "pxr/imaging/hd/sceneIndex.h"

PXR_NAMESPACE_OPEN_SCOPE

#define HDSCENEINDEXPLUGINREGISTRY_TOKENS \
    ((rendererDisplayName, "__rendererDisplayName")) \


TF_DECLARE_PUBLIC_TOKENS(HdSceneIndexPluginRegistryTokens, HD_API,
    HDSCENEINDEXPLUGINREGISTRY_TOKENS);



class HdSceneIndexPlugin;

class HdSceneIndexPluginRegistry final  : public HfPluginRegistry
{
public:
    ///
    /// Returns the singleton registry for \c HdSceneIndexPlugin
    ///
    HD_API
    static HdSceneIndexPluginRegistry &GetInstance();

    ///
    /// Entry point for defining an HdSceneIndexPlugin plugin.
    ///
    template<typename T, typename... Bases>
    static void Define();

    ///
    /// Given a specific scene index plug-in id, give the plug-in a chance
    /// to add scene indices to the end of the chain. Return value is the
    /// last scene index -- or inputScene if the plug-in chooses not to act.
    /// Input arguments may be nullptr if not relevant to this plug-in.
    HD_API
    HdSceneIndexBaseRefPtr AppendSceneIndex(
        const TfToken &sceneIndexPluginId,
        const HdSceneIndexBaseRefPtr &inputScene,
        const HdContainerDataSourceHandle &inputArgs);

    ///
    /// Append scene indices generated by plug-ins registered (via 
    /// RegisterSceneIndexForRenderer) for this renderer. Return value is the
    /// last scene index -- or inputScene if no plugins are registered or
    /// taking action. This also includes plug-ins registered for all
    /// renderers (via an empty rendererDisplayName) to be added in advance
    /// of any registered for the specified rendeer.
    HD_API
    HdSceneIndexBaseRefPtr AppendSceneIndicesForRenderer(
        const std::string &rendererDisplayName,
        const HdSceneIndexBaseRefPtr &inputScene,
        const std::string &renderInstanceId=std::string());

    enum InsertionOrder
    {
        InsertionOrderAtStart,
        InsertionOrderAtEnd,
    };

    using InsertionPhase = int;

    ///
    /// Register a scene index to be instantiated for a specified 
    /// renderer (or all renderers if rendererDisplayName is empty).
    /// 
    /// Insertion phase is a broad ordering value with lower values indicating
    /// earlier instantiation (possibly given render plugin-specific meaning
    /// via enum values). Insertion order indicates whether this entry
    /// should go at the start or end of the specified phase.
    HD_API
    void RegisterSceneIndexForRenderer(
        const std::string &rendererDisplayName,
        const TfToken &sceneIndexPluginId,
        const HdContainerDataSourceHandle &inputArgs,
        InsertionPhase insertionPhase,
        InsertionOrder insertionOrder);


    using SceneIndexAppendCallback = 
        std::function<
            HdSceneIndexBaseRefPtr(
                const std::string &renderInstanceId,
                const HdSceneIndexBaseRefPtr &inputScene,
                const HdContainerDataSourceHandle &inputArgs)>;

    ///
    /// Register a scene index to be instantiated via a callback for a
    /// specified renderer (or all renderers if rendererDisplayName is empty).
    ///
    /// This is most useful for application-specific behavior which wants to
    /// append and manage scene index instances associated with a specific
    /// render. To aid in that association, the callback is provided a
    /// renderInstanceId value typically defined by the application itself.
    ///
    /// Insertion phase is a broad ordering value with lower values indicating
    /// earlier instantiation (possibly given render plugin-specific meaning
    /// via enum values). Insertion order indicates whether this entry
    /// should go at the start or end of the specified phase.
    ///
    /// \note This method should be invoked *before* render index construction
    ///       when Hydra scene index emulation is enabled.
    ///
    HD_API
    void RegisterSceneIndexForRenderer(
        const std::string &rendererDisplayName,
        SceneIndexAppendCallback callback,
        const HdContainerDataSourceHandle &inputArgs,
        InsertionPhase insertionPhase,
        InsertionOrder insertionOrder);



protected:

     void _CollectAdditionalMetadata(
        const PlugRegistry &plugRegistry, const TfType &pluginType) override;

private:
    friend class TfSingleton<HdSceneIndexPluginRegistry>;
    
    // Singleton gets private constructed
    HdSceneIndexPluginRegistry();
    ~HdSceneIndexPluginRegistry() override;

    HdSceneIndexPlugin *_GetSceneIndexPlugin(const TfToken &pluginId);

    struct _Entry
    {
        _Entry(const TfToken &sceneIndexPluginId,
                const HdContainerDataSourceHandle &args)
        : sceneIndexPluginId(sceneIndexPluginId)
        , args(args)
        {}

        _Entry(SceneIndexAppendCallback callback,
                const HdContainerDataSourceHandle &args)
        : args(args)
        , callback(callback)
        {}

        TfToken sceneIndexPluginId;
        HdContainerDataSourceHandle args;
        SceneIndexAppendCallback callback;
    };

    using _EntryList = std::vector<_Entry>;
    using _PhasesMap = std::map<InsertionPhase, _EntryList>;
    using _RenderersMap = std::map<std::string, _PhasesMap>;

    HdSceneIndexBaseRefPtr _AppendForPhases(
        const HdSceneIndexBaseRefPtr &inputScene,
        const _PhasesMap &phasesMap,
        const HdContainerDataSourceHandle &argsUnderlay,
        const std::string &renderInstanceId);

    _RenderersMap _sceneIndicesForRenderers;

    // Used to track plugins whose plugInfo entries contain "loadWithRenderer"
    // values to load when the specified renderer or renderers are used.
    // Loading the plug-in allows for further registration code to run when
    // a plug-in wouldn't be loaded elsewhere.
    using _PreloadMap = std::map<std::string, TfTokenVector>;
    _PreloadMap _preloadsForRenderer;

};

template<typename T, typename... Bases>
void HdSceneIndexPluginRegistry::Define()
{
    HfPluginRegistry::Define<T, HdSceneIndexPlugin, Bases...>();
}

PXR_NAMESPACE_CLOSE_SCOPE

#endif // PXR_IMAGING_HD_SCENE_INDEX_PLUGIN_REGISTRY_H