76 lines
2.2 KiB
C++
76 lines
2.2 KiB
C++
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#pragma once
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#include <glibmm/dispatcher.h>
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#include <sigc++/signal.h>
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#include <functional>
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#include <mutex>
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#include <queue>
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#include <thread>
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#include <tuple>
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#include <type_traits>
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#include <utility>
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namespace waybar {
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/**
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* Thread-safe signal wrapper.
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* Uses Glib::Dispatcher to pass events to another thread and locked queue to pass the arguments.
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*/
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template <typename... Args>
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struct SafeSignal : sigc::signal<void(std::decay_t<Args>...)> {
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public:
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SafeSignal() { dp_.connect(sigc::mem_fun(*this, &SafeSignal::handle_event)); }
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template <typename... EmitArgs>
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void emit(EmitArgs&&... args) {
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if (main_tid_ == std::this_thread::get_id()) {
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/*
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* Bypass the queue if the method is called the main thread.
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* Ensures that events emitted from the main thread are processed synchronously and saves a
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* few CPU cycles on locking/queuing.
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* As a downside, this makes main thread events prioritized over the other threads and
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* disrupts chronological order.
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*/
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signal_t::emit(std::forward<EmitArgs>(args)...);
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} else {
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{
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std::unique_lock lock(mutex_);
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queue_.emplace(std::forward<EmitArgs>(args)...);
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}
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dp_.emit();
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}
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}
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template <typename... EmitArgs>
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inline void operator()(EmitArgs&&... args) {
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emit(std::forward<EmitArgs>(args)...);
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}
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protected:
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using signal_t = sigc::signal<void(std::decay_t<Args>...)>;
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using slot_t = decltype(std::declval<signal_t>().make_slot());
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using arg_tuple_t = std::tuple<std::decay_t<Args>...>;
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// ensure that unwrapped methods are not accessible
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using signal_t::emit_reverse;
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using signal_t::make_slot;
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void handle_event() {
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for (std::unique_lock lock(mutex_); !queue_.empty(); lock.lock()) {
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auto args = queue_.front();
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queue_.pop();
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lock.unlock();
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std::apply(cached_fn_, args);
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}
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}
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Glib::Dispatcher dp_;
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std::mutex mutex_;
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std::queue<arg_tuple_t> queue_;
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const std::thread::id main_tid_ = std::this_thread::get_id();
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// cache functor for signal emission to avoid recreating it on each event
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const slot_t cached_fn_ = make_slot();
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};
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} // namespace waybar
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