Add qt_signal_producer.h to git.

Telegram/SourceFiles/core/qt_signal_producer.h

@@ -0,0 +1,82 @@
+/*
+This file is part of Telegram Desktop,
+the official desktop application for the Telegram messaging service.
+
+For license and copyright information please follow this link:
+https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
+*/
+#pragma once
+
+#include "core/sandbox.h"
+
+namespace Core {
+
+// This method allows to create an rpl::producer from a Qt object
+// and a signal with none or one reported value.
+//
+// QtSignalProducer(qtWindow, &QWindow::activeChanged) | rpl::start_
+//
+// This producer values construct a custom event loop leave point.
+// This means that all postponeCall's will be invoked right after
+// the value processing by the current consumer finishes.
+template <typename Object, typename Signal>
+auto QtSignalProducer(Object *object, Signal signal);
+
+namespace details {
+
+template <typename Signal>
+struct QtSignalArgument;
+
+template <typename Class, typename Return, typename Value>
+struct QtSignalArgument<Return(Class::*)(Value)> {
+	using type = Value;
+};
+
+template <typename Class, typename Return>
+struct QtSignalArgument<Return(Class::*)()> {
+	using type = void;
+};
+
+} // namespace details
+
+template <typename Object, typename Signal>
+auto QtSignalProducer(Object *object, Signal signal) {
+	using Value = typename details::QtSignalArgument<Signal>::type;
+	static constexpr auto NoArgument = std::is_same_v<Value, void>;
+	using Produced = std::conditional_t<
+		NoArgument,
+		rpl::empty_value,
+		std::remove_const_t<std::decay_t<Value>>>;
+	const auto guarded = make_weak(object);
+	return rpl::make_producer<Produced>([=](auto consumer) {
+		if (!guarded) {
+			return rpl::lifetime();
+		}
+		const auto connect = [&](auto &&handler) {
+			const auto listener = new QObject(guarded.data());
+			QObject::connect(
+				guarded,
+				signal,
+				listener,
+				std::forward<decltype(handler)>(handler));
+			const auto weak = make_weak(listener);
+			return rpl::lifetime([=] {
+				if (weak) {
+					delete weak;
+				}
+			});
+		};
+		auto put = [=](const Produced &value) {
+			Sandbox::Instance().customEnterFromEventLoop([&] {
+				consumer.put_next_copy(value);
+			});
+		};
+		if constexpr (NoArgument) {
+			return connect([put = std::move(put)] { put({}); });
+		} else {
+			return connect(std::move(put));
+		}
+	});
+}
+
+} // namespace Core