73 lines
2.2 KiB
C++
73 lines
2.2 KiB
C++
// Copyright (c) 2023 Dominic Masters
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//
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// This software is released under the MIT License.
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// https://opensource.org/licenses/MIT
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#pragma once
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#include "assert/assert.hpp"
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namespace Dawn {
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template<class V>
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class StateProperty;
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class StateOwner {
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private:
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std::map<void*, std::vector<std::function<void()>>> effects;
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public:
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/**
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* Invoked event listener for the subclass that listens for all changes
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* to any part of this state updated.
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*/
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virtual void onStateUpdate() = 0;
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/**
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* Creates a new state property and listens for its change.
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*
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* @tparam V The type of the state that is held.
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* @param initial The initial value of this state.
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* @return The state that can then be listened for.
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*/
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template<class V>
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StateProperty<V> useState(V initial) {
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auto property = StateProperty<V>();
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property.value = initial;
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property.owner = this;
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return property;
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}
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/**
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* Listen for changees to a state property and involke the provided func
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* when the value is changed.
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*
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* @tparam V The type of the state property.
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* @param property Property to listen for affect changees to.
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* @param fn The callback to be invoked when the state value changes.
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*/
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template<class V>
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void useEffect(StateProperty<V> &property, const std::function<void()> &fn) {
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this->effects[(void*)&property].push_back(fn);
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}
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/**
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* Internal method (that has to be exposed) to listen for changes for when
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* a state property that belongs to this state owner is updated.
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*
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* @tparam V The value type of the state property.
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* @param prop The property that has its value changed in question.
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* @param n The new, current value of the property.
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* @param o The old, previous value of the property.
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*/
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template<class V>
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void onStatePropertyUpdated(StateProperty<V> *prop, V n, V o) {
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this->onStateUpdate();
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auto eff = &this->effects[prop];
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auto itEff = eff->begin();
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while(itEff != eff->end()) {
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(*itEff)();
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++itEff;
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}
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}
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};
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} |