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Telegram/lib_base/base/invoke_queued.h

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+// This file is part of Desktop App Toolkit,
+// a set of libraries for developing nice desktop applications.
+//
+// For license and copyright information please follow this link:
+// https://github.com/desktop-app/legal/blob/master/LEGAL
+//
+#pragma once
+
+#include <QtCore/QEvent>
+#include <QtCore/QCoreApplication>
+
+#include "base/basic_types.h"
+
+namespace base {
+
+class InvokeQueuedEvent : public QEvent {
+public:
+	static auto Type() {
+		static const auto Result = QEvent::Type(QEvent::registerEventType());
+		return Result;
+	}
+
+	explicit InvokeQueuedEvent(FnMut<void()> &&method)
+	: QEvent(Type())
+	, _method(std::move(method)) {
+	}
+
+	void invoke() {
+		_method();
+	}
+
+private:
+	FnMut<void()> _method;
+
+};
+
+} // namespace base
+
+template <typename Lambda>
+inline void InvokeQueued(const QObject *context, Lambda &&lambda) {
+	QCoreApplication::postEvent(
+		const_cast<QObject*>(context),
+		new base::InvokeQueuedEvent(std::forward<Lambda>(lambda)));
+}
+
+class SingleQueuedInvokation : public QObject {
+public:
+	SingleQueuedInvokation(Fn<void()> callback) : _callback(callback) {
+	}
+	void call() {
+		if (_pending.testAndSetAcquire(0, 1)) {
+			InvokeQueued(this, [this] {
+				if (_pending.testAndSetRelease(1, 0)) {
+					_callback();
+				}
+			});
+		}
+	}
+
+private:
+	Fn<void()> _callback;
+	QAtomicInt _pending = { 0 };
+
+};