task.h

//
// Copyright 2016 Pixar
//
// Licensed under the terms set forth in the LICENSE.txt file available at
// https://openusd.org/license.
//
#ifndef PXR_IMAGING_HD_TASK_H
#define PXR_IMAGING_HD_TASK_H

#include "pxr/pxr.h"
#include "pxr/imaging/hd/api.h"
#include "pxr/imaging/hd/driver.h"
#include "pxr/imaging/hd/version.h"

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

#include "pxr/usd/sdf/path.h"
#include "pxr/base/tf/hashmap.h"
#include "pxr/base/vt/value.h"
#include "pxr/base/vt/dictionary.h"

#include <memory>
#include <vector>
#include <unordered_map>

PXR_NAMESPACE_OPEN_SCOPE


using HdTaskSharedPtr = std::shared_ptr<class HdTask>;
using HdTaskSharedPtrVector = std::vector<HdTaskSharedPtr>;

// We want to use token as a key not std::string, so use an unordered_map over
// VtDictionary
using HdTaskContext = 
    std::unordered_map<TfToken, VtValue, TfToken::HashFunctor>;

class HdTask
{
public:
    HD_API
    HdTask(SdfPath const& id);

    HD_API
    virtual ~HdTask();

    HD_API
    virtual bool IsConverged() const;


    virtual void Sync(HdSceneDelegate* delegate,
                      HdTaskContext* ctx,
                      HdDirtyBits* dirtyBits) = 0;

    virtual void Prepare(HdTaskContext* ctx,
                         HdRenderIndex* renderIndex) = 0;

    virtual void Execute(HdTaskContext* ctx) = 0;

    HD_API
    virtual const TfTokenVector &GetRenderTags() const;

    SdfPath const& GetId() const { return _id; }

    HD_API
    virtual HdDirtyBits GetInitialDirtyBitsMask() const;


protected:
    HD_API
    static bool _HasTaskContextData(HdTaskContext const* ctx,
                                    TfToken const& id);

    template <class T>
    static bool _GetTaskContextData(HdTaskContext const* ctx,
                                    TfToken const& id,
                                    T* outValue);

    template <class T>
    bool _GetTaskParams(HdSceneDelegate* delegate,
                        T* outValue);

    HD_API
    TfTokenVector _GetTaskRenderTags(HdSceneDelegate* delegate);

    template <class T>
    static T _GetDriver(
        HdTaskContext const* ctx,
        TfToken const& driverName);

private:
    SdfPath _id;

    HdTask()                           = delete;
    HdTask(const HdTask &)             = delete;
    HdTask &operator =(const HdTask &) = delete;
};

// Inline template body
template <class T>
bool
HdTask::_GetTaskContextData(HdTaskContext const* ctx,
                            TfToken const& id,
                            T* outValue)
{
    TF_DEV_AXIOM(outValue != nullptr);

    if (!ctx) {
        return false;
    }

    HdTaskContext::const_iterator valueIt = ctx->find(id);
    if (valueIt == ctx->cend()) {
        TF_CODING_ERROR("Token %s missing from task context", id.GetText());
        return false;
    }

    const VtValue &valueVt = (valueIt->second);
    if (!valueVt.IsHolding<T>()) {
        TF_CODING_ERROR("Token %s in task context is of mismatched type",
                        id.GetText());
        return false;
    }

    *outValue = valueVt.UncheckedGet<T>();

    return true;
}

template <class T>
bool
HdTask::_GetTaskParams(HdSceneDelegate* delegate,
                       T*               outValue)
{
    TF_DEV_AXIOM(outValue != nullptr);

    SdfPath const& taskId = GetId();

    VtValue valueVt = delegate->Get(taskId, HdTokens->params);
    if (!valueVt.IsHolding<T>()) {
        TF_CODING_ERROR("Task params for %s is of unexpected type",
                        taskId.GetText());
        return false;
    }

    *outValue = valueVt.UncheckedGet<T>();

    return true;
}

template <class T>
T
HdTask::_GetDriver(
    HdTaskContext const* ctx,
    TfToken const& driverName)
{
    auto it = ctx->find(HdTokens->drivers);
    if (it != ctx->end()) {
        VtValue const& value = it->second;
        if (value.IsHolding<HdDriverVector>()) {
            HdDriverVector const& drivers= value.UncheckedGet<HdDriverVector>();
            for (HdDriver* hdDriver : drivers) {
                if (hdDriver->name == driverName) {
                    if (hdDriver->driver.IsHolding<T>()) {
                        return hdDriver->driver.UncheckedGet<T>();
                    }
                }
            }
        }
    }

    return nullptr;
}

PXR_NAMESPACE_CLOSE_SCOPE

#endif  // PXR_IMAGING_HD_TASK_H