Merge pull request #1244 from alebastr/swaybar-ipc

Yet another swaybar ipc implementation

.github/workflows/freebsd.yml

@@ -13,6 +13,7 @@ jobs:
     - name: Test in FreeBSD VM
       uses: vmactions/freebsd-vm@v0.1.5 # aka FreeBSD 13.0
       with:
+        mem: 2048
         usesh: true
         prepare: |
           export CPPFLAGS=-isystem/usr/local/include LDFLAGS=-L/usr/local/lib # sndio

include/bar.hpp

@@ -8,6 +8,9 @@
 #include <gtkmm/window.h>
 #include <json/json.h>
 
+#include <memory>
+#include <vector>
+
 #include "AModule.hpp"
 #include "xdg-output-unstable-v1-client-protocol.h"
 
@@ -36,6 +39,19 @@ struct bar_margins {
   int left = 0;
 };
 
+struct bar_mode {
+  bar_layer layer;
+  bool      exclusive;
+  bool      passthrough;
+  bool      visible;
+};
+
+#ifdef HAVE_SWAY
+namespace modules::sway {
+class BarIpcClient;
+}
+#endif  // HAVE_SWAY
+
 class BarSurface {
  protected:
   BarSurface() = default;
@@ -54,31 +70,44 @@ class BarSurface {
 
 class Bar {
  public:
+  using bar_mode_map = std::map<std::string_view, struct bar_mode>;
+  static const bar_mode_map     PRESET_MODES;
+  static const std::string_view MODE_DEFAULT;
+  static const std::string_view MODE_INVISIBLE;
+
   Bar(struct waybar_output *w_output, const Json::Value &);
   Bar(const Bar &) = delete;
-  ~Bar() = default;
+  ~Bar();
 
+  void setMode(const std::string_view &);
   void setVisible(bool visible);
   void toggle();
   void handleSignal(int);
 
   struct waybar_output *output;
   Json::Value           config;
-  struct wl_surface *   surface;
-  bool                  exclusive = true;
+  struct wl_surface    *surface;
   bool                  visible = true;
   bool                  vertical = false;
   Gtk::Window           window;
 
+#ifdef HAVE_SWAY
+  std::string bar_id;
+#endif
+
  private:
   void onMap(GdkEventAny *);
   auto setupWidgets() -> void;
   void getModules(const Factory &, const std::string &, Gtk::Box*);
   void setupAltFormatKeyForModule(const std::string &module_name);
   void setupAltFormatKeyForModuleList(const char *module_list_name);
+  void setMode(const bar_mode &);
+
+  /* Copy initial set of modes to allow customization */
+  bar_mode_map configured_modes = PRESET_MODES;
+  std::string  last_mode_{MODE_DEFAULT};
 
   std::unique_ptr<BarSurface>                   surface_impl_;
-  bar_layer                                     layer_;
   Gtk::Box                                      left_;
   Gtk::Box                                      center_;
   Gtk::Box                                      right_;
@@ -86,6 +115,10 @@ class Bar {
   std::vector<std::unique_ptr<waybar::AModule>> modules_left_;
   std::vector<std::unique_ptr<waybar::AModule>> modules_center_;
   std::vector<std::unique_ptr<waybar::AModule>> modules_right_;
+#ifdef HAVE_SWAY
+  using BarIpcClient = modules::sway::BarIpcClient;
+  std::unique_ptr<BarIpcClient> _ipc_client;
+#endif
   std::vector<std::unique_ptr<waybar::AModule>> modules_all_;
 };
 

include/client.hpp

@@ -29,6 +29,7 @@ class Client {
   struct zwp_idle_inhibit_manager_v1 *idle_inhibit_manager = nullptr;
   std::vector<std::unique_ptr<Bar>>   bars;
   Config                              config;
+  std::string                         bar_id;
 
  private:
   Client() = default;

include/modules/sway/bar.hpp

@@ -0,0 +1,49 @@
+#pragma once
+#include <string>
+
+#include "modules/sway/ipc/client.hpp"
+#include "util/SafeSignal.hpp"
+#include "util/json.hpp"
+
+namespace waybar {
+
+class Bar;
+
+namespace modules::sway {
+
+/*
+ * Supported subset of i3/sway IPC barconfig object
+ */
+struct swaybar_config {
+  std::string id;
+  std::string mode;
+  std::string hidden_state;
+};
+
+/**
+ * swaybar IPC client
+ */
+class BarIpcClient {
+ public:
+  BarIpcClient(waybar::Bar& bar);
+
+ private:
+  void onInitialConfig(const struct Ipc::ipc_response& res);
+  void onIpcEvent(const struct Ipc::ipc_response&);
+  void onConfigUpdate(const swaybar_config& config);
+  void onVisibilityUpdate(bool visible_by_modifier);
+  void update();
+
+  Bar&             bar_;
+  util::JsonParser parser_;
+  Ipc              ipc_;
+
+  swaybar_config bar_config_;
+  bool           visible_by_modifier_ = false;
+
+  SafeSignal<bool>           signal_visible_;
+  SafeSignal<swaybar_config> signal_config_;
+};
+
+}  // namespace modules::sway
+}  // namespace waybar

include/util/SafeSignal.hpp

@@ -0,0 +1,75 @@
+#pragma once
+
+#include <glibmm/dispatcher.h>
+#include <sigc++/signal.h>
+
+#include <functional>
+#include <mutex>
+#include <queue>
+#include <thread>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+namespace waybar {
+
+/**
+ * Thread-safe signal wrapper.
+ * Uses Glib::Dispatcher to pass events to another thread and locked queue to pass the arguments.
+ */
+template <typename... Args>
+struct SafeSignal : sigc::signal<void(std::decay_t<Args>...)> {
+ public:
+  SafeSignal() { dp_.connect(sigc::mem_fun(*this, &SafeSignal::handle_event)); }
+
+  template <typename... EmitArgs>
+  void emit(EmitArgs&&... args) {
+    if (main_tid_ == std::this_thread::get_id()) {
+      /*
+       * Bypass the queue if the method is called the main thread.
+       * Ensures that events emitted from the main thread are processed synchronously and saves a
+       * few CPU cycles on locking/queuing.
+       * As a downside, this makes main thread events prioritized over the other threads and
+       * disrupts chronological order.
+       */
+      signal_t::emit(std::forward<EmitArgs>(args)...);
+    } else {
+      {
+        std::unique_lock lock(mutex_);
+        queue_.emplace(std::forward<EmitArgs>(args)...);
+      }
+      dp_.emit();
+    }
+  }
+
+  template <typename... EmitArgs>
+  inline void operator()(EmitArgs&&... args) {
+    emit(std::forward<EmitArgs>(args)...);
+  }
+
+ protected:
+  using signal_t = sigc::signal<void(std::decay_t<Args>...)>;
+  using slot_t = decltype(std::declval<signal_t>().make_slot());
+  using arg_tuple_t = std::tuple<std::decay_t<Args>...>;
+  // ensure that unwrapped methods are not accessible
+  using signal_t::emit_reverse;
+  using signal_t::make_slot;
+
+  void handle_event() {
+    for (std::unique_lock lock(mutex_); !queue_.empty(); lock.lock()) {
+      auto args = queue_.front();
+      queue_.pop();
+      lock.unlock();
+      std::apply(cached_fn_, args);
+    }
+  }
+
+  Glib::Dispatcher        dp_;
+  std::mutex              mutex_;
+  std::queue<arg_tuple_t> queue_;
+  const std::thread::id   main_tid_ = std::this_thread::get_id();
+  // cache functor for signal emission to avoid recreating it on each event
+  const slot_t cached_fn_ = make_slot();
+};
+
+}  // namespace waybar

man/waybar.5.scd.in

@@ -72,14 +72,19 @@ Also a minimal example configuration can be found on the at the bottom of this m
 	typeof: string ++
 	Optional name added as a CSS class, for styling multiple waybars.
 
+*mode* ++
+	typeof: string ++
+	Selects one of the preconfigured display modes. This is an equivalent of the sway-bar(5) *mode* command and supports the same values: *dock*, *hide*, *invisible*, *overlay*. ++
+	Note: *hide* and *invisible* modes may be not as useful without Sway IPC.
+
 *exclusive* ++
 	typeof: bool ++
-	default: *true* unless the layer is set to *overlay* ++
+	default: *true* ++
 	Option to request an exclusive zone from the compositor. Disable this to allow drawing application windows underneath or on top of the bar.
 
 *passthrough* ++
 	typeof: bool ++
-	default: *false* unless the layer is set to *overlay* ++
+	default: *false* ++
 	Option to pass any pointer events to the window under the bar.
 	Intended to be used with either *top* or *overlay* layers and without exclusive zone.
 
@@ -89,6 +94,16 @@ Also a minimal example configuration can be found on the at the bottom of this m
 	Option to disable the use of gtk-layer-shell for popups.
 	Only functional if compiled with gtk-layer-shell support.
 
+*ipc* ++
+	typeof: bool ++
+	default: false ++
+	Option to subscribe to the Sway IPC bar configuration and visibility events and control waybar with *swaymsg bar* commands. ++
+	Requires *bar_id* value from sway configuration to be either passed with the *-b* commandline argument or specified with the *id* option.
+
+*id* ++
+	typeof: string ++
+	*bar_id* for the Sway IPC. Use this if you need to override the value passed with the *-b bar_id* commandline argument for the specific bar instance.
+
 *include* ++
 	typeof: string|array ++
 	Paths to additional configuration files.

meson.build

@@ -178,6 +178,7 @@ endif
 add_project_arguments('-DHAVE_SWAY', language: 'cpp')
 src_files += [
     'src/modules/sway/ipc/client.cpp',
+    'src/modules/sway/bar.cpp',
     'src/modules/sway/mode.cpp',
     'src/modules/sway/language.cpp',
     'src/modules/sway/window.cpp',

src/bar.cpp

@@ -12,6 +12,10 @@
 #include "group.hpp"
 #include "wlr-layer-shell-unstable-v1-client-protocol.h"
 
+#ifdef HAVE_SWAY
+#include "modules/sway/bar.hpp"
+#endif
+
 namespace waybar {
 static constexpr const char* MIN_HEIGHT_MSG =
     "Requested height: {} is less than the minimum height: {} required by the modules";
@@ -24,6 +28,84 @@ static constexpr const char* BAR_SIZE_MSG = "Bar configured (width: {}, height:
 static constexpr const char* SIZE_DEFINED =
     "{} size is defined in the config file so it will stay like that";
 
+const Bar::bar_mode_map Bar::PRESET_MODES = {  //
+    {"default",
+     {// Special mode to hold the global bar configuration
+      .layer = bar_layer::BOTTOM,
+      .exclusive = true,
+      .passthrough = false,
+      .visible = true}},
+    {"dock",
+     {// Modes supported by the sway config; see man sway-bar(5)
+      .layer = bar_layer::BOTTOM,
+      .exclusive = true,
+      .passthrough = false,
+      .visible = true}},
+    {"hide",
+     {//
+      .layer = bar_layer::TOP,
+      .exclusive = false,
+      .passthrough = false,
+      .visible = true}},
+    {"invisible",
+     {//
+      .layer = bar_layer::BOTTOM,
+      .exclusive = false,
+      .passthrough = true,
+      .visible = false}},
+    {"overlay",
+     {//
+      .layer = bar_layer::TOP,
+      .exclusive = false,
+      .passthrough = true,
+      .visible = true}}};
+
+const std::string_view Bar::MODE_DEFAULT = "default";
+const std::string_view Bar::MODE_INVISIBLE = "invisible";
+const std::string_view DEFAULT_BAR_ID = "bar-0";
+
+/* Deserializer for enum bar_layer */
+void from_json(const Json::Value& j, bar_layer& l) {
+  if (j == "bottom") {
+    l = bar_layer::BOTTOM;
+  } else if (j == "top") {
+    l = bar_layer::TOP;
+  } else if (j == "overlay") {
+    l = bar_layer::OVERLAY;
+  }
+}
+
+/* Deserializer for struct bar_mode */
+void from_json(const Json::Value& j, bar_mode& m) {
+  if (j.isObject()) {
+    if (auto v = j["layer"]; v.isString()) {
+      from_json(v, m.layer);
+    }
+    if (auto v = j["exclusive"]; v.isBool()) {
+      m.exclusive = v.asBool();
+    }
+    if (auto v = j["passthrough"]; v.isBool()) {
+      m.passthrough = v.asBool();
+    }
+    if (auto v = j["visible"]; v.isBool()) {
+      m.visible = v.asBool();
+    }
+  }
+}
+
+/* Deserializer for JSON Object -> map<string compatible type, Value>
+ * Assumes that all the values in the object are deserializable to the same type.
+ */
+template <typename Key, typename Value,
+          typename = std::enable_if_t<std::is_convertible<std::string_view, Key>::value>>
+void from_json(const Json::Value& j, std::map<Key, Value>& m) {
+  if (j.isObject()) {
+    for (auto it = j.begin(); it != j.end(); ++it) {
+      from_json(*it, m[it.key().asString()]);
+    }
+  }
+}
+
 #ifdef HAVE_GTK_LAYER_SHELL
 struct GLSSurfaceImpl : public BarSurface, public sigc::trackable {
   GLSSurfaceImpl(Gtk::Window& window, struct waybar_output& output) : window_{window} {
@@ -392,7 +474,6 @@ waybar::Bar::Bar(struct waybar_output* w_output, const Json::Value& w_config)
     : output(w_output),
       config(w_config),
       window{Gtk::WindowType::WINDOW_TOPLEVEL},
-      layer_{bar_layer::BOTTOM},
       left_(Gtk::ORIENTATION_HORIZONTAL, 0),
       center_(Gtk::ORIENTATION_HORIZONTAL, 0),
       right_(Gtk::ORIENTATION_HORIZONTAL, 0),
@@ -404,27 +485,6 @@ waybar::Bar::Bar(struct waybar_output* w_output, const Json::Value& w_config)
   window.get_style_context()->add_class(config["name"].asString());
   window.get_style_context()->add_class(config["position"].asString());
 
-  if (config["layer"] == "top") {
-    layer_ = bar_layer::TOP;
-  } else if (config["layer"] == "overlay") {
-    layer_ = bar_layer::OVERLAY;
-  }
-
-  if (config["exclusive"].isBool()) {
-    exclusive = config["exclusive"].asBool();
-  } else if (layer_ == bar_layer::OVERLAY) {
-    // swaybar defaults: overlay mode does not reserve an exclusive zone
-    exclusive = false;
-  }
-
-  bool passthrough = false;
-  if (config["passthrough"].isBool()) {
-    passthrough = config["passthrough"].asBool();
-  } else if (layer_ == bar_layer::OVERLAY) {
-    // swaybar defaults: overlay mode does not accept pointer events.
-    passthrough = true;
-  }
-
   auto position = config["position"].asString();
 
   if (position == "right" || position == "left") {
@@ -506,15 +566,43 @@ waybar::Bar::Bar(struct waybar_output* w_output, const Json::Value& w_config)
     surface_impl_ = std::make_unique<RawSurfaceImpl>(window, *output);
   }
 
-  surface_impl_->setLayer(layer_);
-  surface_impl_->setExclusiveZone(exclusive);
   surface_impl_->setMargins(margins_);
-  surface_impl_->setPassThrough(passthrough);
   surface_impl_->setPosition(position);
   surface_impl_->setSize(width, height);
 
+  /* Read custom modes if available */
+  if (auto modes = config.get("modes", {}); modes.isObject()) {
+    from_json(modes, configured_modes);
+  }
+
+  /* Update "default" mode with the global bar options */
+  from_json(config, configured_modes[MODE_DEFAULT]);
+
+  if (auto mode = config.get("mode", {}); mode.isString()) {
+    setMode(config["mode"].asString());
+  } else {
+    setMode(MODE_DEFAULT);
+  }
+
   window.signal_map_event().connect_notify(sigc::mem_fun(*this, &Bar::onMap));
 
+#if HAVE_SWAY
+  if (auto ipc = config["ipc"]; ipc.isBool() && ipc.asBool()) {
+    bar_id = Client::inst()->bar_id;
+    if (auto id = config["id"]; id.isString()) {
+      bar_id = id.asString();
+    }
+    if (bar_id.empty()) {
+      bar_id = DEFAULT_BAR_ID;
+    }
+    try {
+      _ipc_client = std::make_unique<BarIpcClient>(*this);
+    } catch (const std::exception& exc) {
+      spdlog::warn("Failed to open bar ipc connection: {}", exc.what());
+    }
+  }
+#endif
+
   setupWidgets();
   window.show_all();
 
@@ -529,6 +617,44 @@ waybar::Bar::Bar(struct waybar_output* w_output, const Json::Value& w_config)
   }
 }
 
+/* Need to define it here because of forward declared members */
+waybar::Bar::~Bar() = default;
+
+void waybar::Bar::setMode(const std::string_view& mode) {
+  using namespace std::literals::string_literals;
+
+  auto style = window.get_style_context();
+  /* remove styles added by previous setMode calls */
+  style->remove_class("mode-"s + last_mode_);
+
+  auto it = configured_modes.find(mode);
+  if (it != configured_modes.end()) {
+    last_mode_ = mode;
+    style->add_class("mode-"s + last_mode_);
+    setMode(it->second);
+  } else {
+    spdlog::warn("Unknown mode \"{}\" requested", mode);
+    last_mode_ = MODE_DEFAULT;
+    style->add_class("mode-"s + last_mode_);
+    setMode(configured_modes.at(MODE_DEFAULT));
+  }
+}
+
+void waybar::Bar::setMode(const struct bar_mode& mode) {
+  surface_impl_->setLayer(mode.layer);
+  surface_impl_->setExclusiveZone(mode.exclusive);
+  surface_impl_->setPassThrough(mode.passthrough);
+
+  if (mode.visible) {
+    window.get_style_context()->remove_class("hidden");
+    window.set_opacity(1);
+  } else {
+    window.get_style_context()->add_class("hidden");
+    window.set_opacity(0);
+  }
+  surface_impl_->commit();
+}
+
 void waybar::Bar::onMap(GdkEventAny*) {
   /*
    * Obtain a pointer to the custom layer surface for modules that require it (idle_inhibitor).
@@ -539,17 +665,7 @@ void waybar::Bar::onMap(GdkEventAny*) {
 
 void waybar::Bar::setVisible(bool value) {
   visible = value;
-  if (!visible) {
-    window.get_style_context()->add_class("hidden");
-    window.set_opacity(0);
-    surface_impl_->setLayer(bar_layer::BOTTOM);
-  } else {
-    window.get_style_context()->remove_class("hidden");
-    window.set_opacity(1);
-    surface_impl_->setLayer(layer_);
-  }
-  surface_impl_->setExclusiveZone(exclusive && visible);
-  surface_impl_->commit();
+  setMode(visible ? MODE_DEFAULT : MODE_INVISIBLE);
 }
 
 void waybar::Bar::toggle() { setVisible(!visible); }

src/client.cpp

@@ -199,7 +199,6 @@ int waybar::Client::main(int argc, char *argv[]) {
   bool        show_version = false;
   std::string config_opt;
   std::string style_opt;
-  std::string bar_id;
   std::string log_level;
   auto        cli = clara::detail::Help(show_help) |
              clara::detail::Opt(show_version)["-v"]["--version"]("Show version") |

src/modules/sway/bar.cpp

@@ -0,0 +1,107 @@
+#include "modules/sway/bar.hpp"
+
+#include <fmt/ostream.h>
+#include <spdlog/spdlog.h>
+
+#include <stdexcept>
+
+#include "bar.hpp"
+#include "modules/sway/ipc/ipc.hpp"
+
+namespace waybar::modules::sway {
+
+BarIpcClient::BarIpcClient(waybar::Bar& bar) : bar_{bar} {
+  {
+    sigc::connection handle =
+        ipc_.signal_cmd.connect(sigc::mem_fun(*this, &BarIpcClient::onInitialConfig));
+    ipc_.sendCmd(IPC_GET_BAR_CONFIG, bar_.bar_id);
+
+    handle.disconnect();
+  }
+
+  signal_config_.connect(sigc::mem_fun(*this, &BarIpcClient::onConfigUpdate));
+  signal_visible_.connect(sigc::mem_fun(*this, &BarIpcClient::onVisibilityUpdate));
+
+  ipc_.subscribe(R"(["bar_state_update", "barconfig_update"])");
+  ipc_.signal_event.connect(sigc::mem_fun(*this, &BarIpcClient::onIpcEvent));
+  // Launch worker
+  ipc_.setWorker([this] {
+    try {
+      ipc_.handleEvent();
+    } catch (const std::exception& e) {
+      spdlog::error("BarIpcClient::handleEvent {}", e.what());
+    }
+  });
+}
+
+struct swaybar_config parseConfig(const Json::Value& payload) {
+  swaybar_config conf;
+  if (auto id = payload["id"]; id.isString()) {
+    conf.id = id.asString();
+  }
+  if (auto mode = payload["mode"]; mode.isString()) {
+    conf.mode = mode.asString();
+  }
+  if (auto hs = payload["hidden_state"]; hs.isString()) {
+    conf.hidden_state = hs.asString();
+  }
+  return conf;
+}
+
+void BarIpcClient::onInitialConfig(const struct Ipc::ipc_response& res) {
+  auto payload = parser_.parse(res.payload);
+  if (auto success = payload.get("success", true); !success.asBool()) {
+    auto err = payload.get("error", "Unknown error");
+    throw std::runtime_error(err.asString());
+  }
+  auto config = parseConfig(payload);
+  onConfigUpdate(config);
+}
+
+void BarIpcClient::onIpcEvent(const struct Ipc::ipc_response& res) {
+  try {
+    auto payload = parser_.parse(res.payload);
+    if (auto id = payload["id"]; id.isString() && id.asString() != bar_.bar_id) {
+      spdlog::trace("swaybar ipc: ignore event for {}", id.asString());
+      return;
+    }
+    if (payload.isMember("visible_by_modifier")) {
+      // visibility change for hidden bar
+      signal_visible_(payload["visible_by_modifier"].asBool());
+    } else {
+      // configuration update
+      auto config = parseConfig(payload);
+      signal_config_(std::move(config));
+    }
+  } catch (const std::exception& e) {
+    spdlog::error("BarIpcClient::onEvent {}", e.what());
+  }
+}
+
+void BarIpcClient::onConfigUpdate(const swaybar_config& config) {
+  spdlog::info("config update for {}: id {}, mode {}, hidden_state {}",
+               bar_.bar_id,
+               config.id,
+               config.mode,
+               config.hidden_state);
+  bar_config_ = config;
+  update();
+}
+
+void BarIpcClient::onVisibilityUpdate(bool visible_by_modifier) {
+  spdlog::debug("visiblity update for {}: {}", bar_.bar_id, visible_by_modifier);
+  visible_by_modifier_ = visible_by_modifier;
+  update();
+}
+
+void BarIpcClient::update() {
+  bool visible = visible_by_modifier_;
+  if (bar_config_.mode == "invisible") {
+    visible = false;
+  } else if (bar_config_.mode != "hide" || bar_config_.hidden_state != "hide") {
+    visible = true;
+  }
+  bar_.setMode(visible ? bar_config_.mode : Bar::MODE_INVISIBLE);
+}
+
+}  // namespace waybar::modules::sway

test/GlibTestsFixture.hpp

@@ -0,0 +1,24 @@
+#pragma once
+#include <glibmm/main.h>
+/**
+ * Minimal Glib application to be used for tests that require Glib main loop
+ */
+class GlibTestsFixture : public sigc::trackable {
+ public:
+  GlibTestsFixture() : main_loop_{Glib::MainLoop::create()} {}
+
+  void setTimeout(int timeout) {
+    Glib::signal_timeout().connect_once([]() { throw std::runtime_error("Test timed out"); },
+                                        timeout);
+  }
+
+  void run(std::function<void()> fn) {
+    Glib::signal_idle().connect_once(fn);
+    main_loop_->run();
+  }
+
+  void quit() { main_loop_->quit(); }
+
+ protected:
+  Glib::RefPtr<Glib::MainLoop> main_loop_;
+};

test/SafeSignal.cpp

@@ -0,0 +1,145 @@
+#define CATCH_CONFIG_RUNNER
+#include "util/SafeSignal.hpp"
+
+#include <glibmm.h>
+
+#include <catch2/catch.hpp>
+#include <thread>
+#include <type_traits>
+
+#include "GlibTestsFixture.hpp"
+
+using namespace waybar;
+
+template <typename T>
+using remove_cvref_t = typename std::remove_cv<typename std::remove_reference<T>::type>::type;
+
+/**
+ * Basic sanity test for SafeSignal:
+ * check that type deduction works, events are delivered and the order is right
+ * Running this with -fsanitize=thread should not fail
+ */
+TEST_CASE_METHOD(GlibTestsFixture, "SafeSignal basic functionality", "[signal][thread][util]") {
+  const int NUM_EVENTS = 100;
+  int       count = 0;
+  int       last_value = 0;
+
+  SafeSignal<int, std::string> test_signal;
+
+  const auto  main_tid = std::this_thread::get_id();
+  std::thread producer;
+
+  // timeout the test in 500ms
+  setTimeout(500);
+
+  test_signal.connect([&](auto val, auto str) {
+    static_assert(std::is_same<int, decltype(val)>::value);
+    static_assert(std::is_same<std::string, decltype(str)>::value);
+    // check that we're in the same thread as the main loop
+    REQUIRE(std::this_thread::get_id() == main_tid);
+    // check event order
+    REQUIRE(val == last_value + 1);
+
+    last_value = val;
+    if (++count >= NUM_EVENTS) {
+      this->quit();
+    };
+  });
+
+  run([&]() {
+    // check that events from the same thread are delivered and processed synchronously
+    test_signal.emit(1, "test");
+    REQUIRE(count == 1);
+
+    // start another thread and generate events
+    producer = std::thread([&]() {
+      for (auto i = 2; i <= NUM_EVENTS; ++i) {
+        test_signal.emit(i, "test");
+      }
+    });
+  });
+  producer.join();
+  REQUIRE(count == NUM_EVENTS);
+}
+
+template <typename T>
+struct TestObject {
+  T        value;
+  unsigned copied = 0;
+  unsigned moved = 0;
+
+  TestObject(const T& v) : value(v){};
+  ~TestObject() = default;
+
+  TestObject(const TestObject& other)
+      : value(other.value), copied(other.copied + 1), moved(other.moved) {}
+
+  TestObject(TestObject&& other) noexcept
+      : value(std::move(other.value)),
+        copied(std::exchange(other.copied, 0)),
+        moved(std::exchange(other.moved, 0) + 1) {}
+
+  TestObject& operator=(const TestObject& other) {
+    value = other.value;
+    copied = other.copied + 1;
+    moved = other.moved;
+    return *this;
+  }
+
+  TestObject& operator=(TestObject&& other) noexcept {
+    value = std::move(other.value);
+    copied = std::exchange(other.copied, 0);
+    moved = std::exchange(other.moved, 0) + 1;
+    return *this;
+  }
+
+  bool operator==(T other) const { return value == other; }
+       operator T() const { return value; }
+};
+
+/*
+ * Check the number of copies/moves performed on the object passed through SafeSignal
+ */
+TEST_CASE_METHOD(GlibTestsFixture, "SafeSignal copy/move counter", "[signal][thread][util]") {
+  const int NUM_EVENTS = 3;
+  int       count = 0;
+
+  SafeSignal<TestObject<int>> test_signal;
+
+  std::thread producer;
+
+  // timeout the test in 500ms
+  setTimeout(500);
+
+  test_signal.connect([&](auto& val) {
+    static_assert(std::is_same<TestObject<int>, remove_cvref_t<decltype(val)>>::value);
+
+    /* explicit move in the producer thread */
+    REQUIRE(val.moved <= 1);
+    /* copy within the SafeSignal queuing code */
+    REQUIRE(val.copied <= 1);
+
+    if (++count >= NUM_EVENTS) {
+      this->quit();
+    };
+  });
+
+  run([&]() {
+    test_signal.emit(1);
+    REQUIRE(count == 1);
+    producer = std::thread([&]() {
+      for (auto i = 2; i <= NUM_EVENTS; ++i) {
+        TestObject<int> t{i};
+        // check that signal.emit accepts moved objects
+        test_signal.emit(std::move(t));
+      }
+    });
+  });
+  producer.join();
+  REQUIRE(count == NUM_EVENTS);
+}
+
+int main(int argc, char* argv[]) {
+  Glib::init();
+  return Catch::Session().run(argc, argv);
+}

test/meson.build

@@ -2,6 +2,7 @@ test_inc = include_directories('../include')
 test_dep = [
     catch2,
     fmt,
+    gtkmm,
     jsoncpp,
     spdlog,
 ]
@@ -14,8 +15,21 @@ config_test = executable(
     include_directories: test_inc,
 )
 
+safesignal_test = executable(
+    'safesignal_test',
+    'SafeSignal.cpp',
+    dependencies: test_dep,
+    include_directories: test_inc,
+)
+
 test(
     'Configuration test',
     config_test,
     workdir: meson.source_root(),
 )
+
+test(
+    'SafeSignal test',
+    safesignal_test,
+    workdir: meson.source_root(),
+)