Allow libraries use their own langpacks.

gyp/sources.txt

@@ -130,6 +130,8 @@
 <(src_loc)/ui/main_queue_processor.cpp
 <(src_loc)/ui/main_queue_processor.h
 <(src_loc)/ui/painter.h
+<(src_loc)/ui/ph.cpp
+<(src_loc)/ui/ph.h
 <(src_loc)/ui/rect_part.h
 <(src_loc)/ui/round_rect.cpp
 <(src_loc)/ui/round_rect.h

ui/ph.cpp

@@ -0,0 +1,37 @@
+// 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
+//
+#include "ui/ph.h"
+
+namespace ph {
+namespace {
+
+int &PhraseCounter() {
+	static auto result = 0;
+	return result;
+}
+
+} // namespace
+
+phrase::phrase(const QString &initial) : value(initial) {
+	if (auto &counter = PhraseCounter()) {
+		++counter;
+	}
+}
+
+now_t start_phrase_count() {
+	PhraseCounter() = 1;
+	return now;
+}
+
+now_t check_phrase_count(int count) {
+	Expects(PhraseCounter() == count + 1);
+
+	PhraseCounter() = 0;
+	return now;
+}
+
+} // namespace ph

ui/ph.h

@@ -0,0 +1,60 @@
+// 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
+
+namespace ph {
+
+struct now_t {
+};
+
+inline constexpr auto now = now_t();
+
+struct I {
+	QString operator()(const QString &value) const { return value; };
+};
+
+template <typename P>
+using Result = decltype(std::declval<P>()(QString()));
+
+struct phrase {
+	phrase(const QString &initial);
+	template <std::size_t Size>
+	phrase(const char (&initial)[Size])
+	: phrase(QString::fromUtf8(initial, Size - 1)) {
+	}
+
+	template <typename P = I, typename = Result<P>>
+	Result<P> operator()(ph::now_t, P p = P()) const {
+		return p(value.current());
+	};
+	template <typename P = I, typename = Result<P>>
+	rpl::producer<Result<P>> operator()(P p = P()) const {
+		return value.value() | rpl::map(p);
+	};
+
+	rpl::variable<QString> value;
+};
+
+now_t start_phrase_count();
+now_t check_phrase_count(int count);
+
+namespace details {
+
+template <int Count>
+using phrase_value_array = std::array<
+	std::pair<not_null<phrase*>, rpl::producer<QString>>,
+	Count>;
+
+template <int Count>
+void set_values(phrase_value_array<Count> &&data) {
+	for (auto &[single, value] : data) {
+		single->value = std::move(value);
+	}
+}
+
+} // namespace details
+} // namespace ph