Attempt at supporting locale and timezones (#1)

include/modules/clock.hpp

@@ -20,6 +20,9 @@ class Clock : public ALabel {
 
  private:
   util::SleeperThread thread_;
+  std::locale locale_;
+  const date::time_zone* time_zone_;
+  bool fixed_time_zone_;
 };
 
 }  // namespace waybar::modules

man/waybar-clock.5.scd

@@ -18,13 +18,19 @@ The *clock* module displays the current date and time.
 *format*: ++
 	typeof: string ++
 	default: {:%H:%M} ++
-	The format, how the date and time should be displayed.
+	The format, how the date and time should be displayed. ++
+	It uses the format of the date library. See https://howardhinnant.github.io/date/date.html#to_stream_formatting for details.
 
 *timezone*: ++
 	typeof: string ++
 	default: inferred local timezone ++
 	The timezone to display the time in, e.g. America/New_York.
 
+*locale*: ++
+	typeof: string ++
+	default: inferred from current locale ++
+	A locale to be used to display the time. Intended to render times in custom timezones with the proper language and format.
+
 *max-length*: ++
 	typeof: integer ++
 	The maximum length in character the module should display.

src/modules/clock.cpp

@@ -1,7 +1,20 @@
 #include "modules/clock.hpp"
 
 waybar::modules::Clock::Clock(const std::string& id, const Json::Value& config)
-    : ALabel(config, "clock", id, "{:%H:%M}", 60) {
+    : ALabel(config, "clock", id, "{:%H:%M}", 60)
+    , fixed_time_zone_(false)
+{
+  if (config_["timezone"].isString()) {
+    time_zone_ = date::locate_zone(config_["timezone"].asString());
+    fixed_time_zone_ = true;
+  }
+
+  if (config_["locale"].isString()) {
+    locale_ = std::locale(config_["locale"].asString());
+  } else {
+    locale_ = std::locale("");
+  }
+
   thread_ = [this] {
     dp.emit();
     auto now = std::chrono::system_clock::now();
@@ -11,23 +24,28 @@ waybar::modules::Clock::Clock(const std::string& id, const Json::Value& config)
   };
 }
 
+using zoned_time = date::zoned_time<std::chrono::system_clock::duration>;
+
+struct waybar_time {
+  std::locale locale;
+  zoned_time ztime;
+};
+
 auto waybar::modules::Clock::update() -> void {
-  tzset(); // Update timezone information
-  const date::time_zone* zone;
-  auto now = std::chrono::floor<std::chrono::seconds>(std::chrono::system_clock::now());
-  if (config_["timezone"].isString()) {
-    zone = date::locate_zone(config_["timezone"].asString());
-  } else {
-    zone = date::current_zone();
+  if (!fixed_time_zone_) {
+    // Time zone can change. Be sure to pick that.
+    time_zone_ = date::current_zone();
   }
-  auto localtime = date::make_zoned(zone, now);
-  auto text = fmt::format(format_, localtime);
+  auto now = std::chrono::system_clock::now();
+  waybar_time wtime = {locale_, date::make_zoned(time_zone_, now)};
+
+  auto text = fmt::format(format_, wtime);
   label_.set_markup(text);
 
   if (tooltipEnabled()) {
     if (config_["tooltip-format"].isString()) {
       auto tooltip_format = config_["tooltip-format"].asString();
-      auto tooltip_text = fmt::format(tooltip_format, localtime);
+      auto tooltip_text = fmt::format(tooltip_format, wtime);
       label_.set_tooltip_text(tooltip_text);
     } else {
       label_.set_tooltip_text(text);
@@ -35,22 +53,10 @@ auto waybar::modules::Clock::update() -> void {
   }
 }
 
-template <typename ZonedTimeInner>
-struct fmt::formatter<date::zoned_time<ZonedTimeInner>> {
-
-  std::string *format_string;
-
-  constexpr auto parse(format_parse_context& ctx) {
-    format_string = new std::string[1];
-    auto it = ctx.begin(), end = ctx.end();
-    while (it != (end - 1)) {
-      *format_string += *it++;
-    }
-    return it;
-  }
-
+template <>
+struct fmt::formatter<waybar_time> : fmt::formatter<std::tm> {
   template <typename FormatContext>
-  auto format(const date::zoned_time<ZonedTimeInner>& d, FormatContext& ctx) {
-    return format_to(ctx.out(), "{}", date::format(std::locale(""), *format_string, d));
+  auto format(const waybar_time& t, FormatContext& ctx) {
+    return format_to(ctx.out(), "{}", date::format(t.locale, fmt::to_string(tm_format), t.ztime));
   }
 };