binding_evaluator.h

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/*
  This file is part of KDBindings.
 
  SPDX-FileCopyrightText: 2021 Klarälvdalens Datakonsult AB, a KDAB Group company <info@kdab.com>
  Author: Sean Harmer <sean.harmer@kdab.com>
 
  SPDX-License-Identifier: MIT
 
  Contact KDAB at <info@kdab.com> for commercial licensing options.
*/
 
#pragma once
 
#include <functional>
#include <map>
#include <memory>
 
namespace KDBindings {
 
class BindingEvaluator
{
    // We use pimpl here so that we can pass evaluators around by value (copies)
    // yet each copy refers to the same set of data
    struct Private {
        // TODO: Use std::vector here?
        std::map<int, std::function<void()>> m_bindingEvalFunctions;
        int m_currentId;
    };
 
public:
    BindingEvaluator() = default;
 
    BindingEvaluator(const BindingEvaluator &) noexcept = default;
 
    BindingEvaluator &operator=(const BindingEvaluator &) noexcept = default;
 
    BindingEvaluator(BindingEvaluator &&other) noexcept = delete;
 
    BindingEvaluator &operator=(BindingEvaluator &&other) noexcept = delete;
 
    void evaluateAll() const
    {
        // a std::map's ordering is deterministic, so the bindings are evaluated
        // in the order they were inserted, ensuring correct transitive dependency
        // evaluation.
        for (auto &[id, func] : m_d->m_bindingEvalFunctions)
            func();
    }
 
private:
    template<typename BindingType>
    int insert(BindingType *binding)
    {
        m_d->m_bindingEvalFunctions.insert({ ++(m_d->m_currentId),
                                             [=]() { binding->evaluate(); } });
        return m_d->m_currentId;
    }
 
    void remove(int id)
    {
        m_d->m_bindingEvalFunctions.erase(id);
    }
 
    std::shared_ptr<Private> m_d{ std::make_shared<Private>() };
 
    template<typename T, typename UpdaterT>
    friend class Binding;
};
 
class ImmediateBindingEvaluator final : public BindingEvaluator
{
public:
    static inline ImmediateBindingEvaluator instance()
    {
        static ImmediateBindingEvaluator evaluator;
        return evaluator;
    }
};
 
} // namespace KDBindings