APropertyPrecomputed.h

/*
 * AUI Framework - Declarative UI toolkit for modern C++20
 * Copyright (C) 2020-2024 Alex2772 and Contributors
 *
 * SPDX-License-Identifier: MPL-2.0
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */
 
#pragma once
 
#include "AObjectBase.h"
#include "ASignal.h"
 
namespace aui::property_precomputed {
namespace detail {
struct DependencyObserver : AObjectBase {
public:
    virtual void invalidate() = 0;
};
 
struct API_AUI_CORE DependencyObserverRegistrar {
    explicit DependencyObserverRegistrar(DependencyObserver& observer);
    ~DependencyObserverRegistrar();
 
private:
    DependencyObserver* mPrevObserver;
};
}   // namespace detail

API_AUI_CORE void addDependency(const AAbstractSignal& signal);
 
}   // namespace aui::property_precomputed

template<typename T>
struct APropertyPrecomputed final : aui::property_precomputed::detail::DependencyObserver {
    using Underlying = T;
    using Factory = std::function<T()>;
 
    template<aui::factory<T> Factory>
    APropertyPrecomputed(Factory&& expression): mCurrentValue([this, expression = std::forward<Factory>(expression)] { // NOLINT(*-explicit-constructor)
      clearSignals();
      aui::property_precomputed::detail::DependencyObserverRegistrar r(*this);
      return expression();
    }) {
 
    }
 
    APropertyPrecomputed(const APropertyPrecomputed&) = delete;
    APropertyPrecomputed(APropertyPrecomputed&&) noexcept = delete;
 
    template <ASignalInvokable SignalInvokable>
    void operator^(SignalInvokable&& t) {
        t.invokeSignal(nullptr);
    }
 
    void invalidate() override {
        mCurrentValue.reset();
        if (this->changed) {
            emit this->changed(value());
        }
    }
 
    AObjectBase* boundObject() {
        return this;
    }
 
    [[nodiscard]]
    const T& value() const {
        return mCurrentValue;
    }
 
    [[nodiscard]]
    operator const T&() const {
        return value();
    }
 
    [[nodiscard]]
    const T& operator*() const {
        return value();
    }
 
signals:
    emits<T> changed;
 
private:
    aui::lazy<T> mCurrentValue;
};
 
template<aui::invocable<> Factory>
APropertyPrecomputed(Factory&& f) -> APropertyPrecomputed<std::decay_t<std::invoke_result_t<Factory>>>;
 
static_assert(APropertyReadable<APropertyPrecomputed<int>>, "APropertyPrecomputed must be a APropertyReadable");

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