Add backlight module

Monitor the backlight level via udev. Poll every `interval` as well,
in case backlight udev events aren't supported.

include/factory.hpp

@@ -19,6 +19,7 @@
 #ifdef HAVE_LIBPULSE
 #include "modules/pulseaudio.hpp"
 #endif
+#include "modules/backlight.hpp"
 #include "modules/custom.hpp"
 
 namespace waybar {

include/modules/backlight.hpp

@@ -0,0 +1,65 @@
+#pragma once
+
+#include <optional>
+#include <string>
+#include <string_view>
+#include <vector>
+
+#include "ALabel.hpp"
+#include "util/json.hpp"
+#include "util/sleeper_thread.hpp"
+
+struct udev;
+struct udev_device;
+
+namespace waybar::modules {
+
+class Backlight : public ALabel {
+  class BacklightDev {
+  public:
+    BacklightDev() = default;
+    BacklightDev(std::string name, int actual, int max);
+    std::string_view name() const;
+    int get_actual() const;
+    void set_actual(int actual);
+    int get_max() const;
+    void set_max(int max);
+    friend inline bool operator==(const BacklightDev &lhs,
+                                  const BacklightDev &rhs) {
+      return lhs.name_ == rhs.name_ && lhs.actual_ == rhs.actual_ &&
+             lhs.max_ == rhs.max_;
+    }
+
+  private:
+    std::string name_;
+    int actual_ = 1;
+    int max_ = 1;
+  };
+
+public:
+  Backlight(const std::string &, const Json::Value &);
+  ~Backlight();
+  auto update() -> void;
+
+private:
+  template <class ForwardIt>
+  static const BacklightDev *best_device(ForwardIt first, ForwardIt last,
+                                         std::string_view);
+  template <class ForwardIt, class Inserter>
+  static void upsert_device(ForwardIt first, ForwardIt last, Inserter inserter,
+                            udev_device *dev);
+  template <class ForwardIt, class Inserter>
+  static void enumerate_devices(ForwardIt first, ForwardIt last,
+                                Inserter inserter, udev *udev);
+
+  const std::string name_;
+  const std::string preferred_device_;
+  static constexpr int EPOLL_MAX_EVENTS = 16;
+
+  waybar::util::SleeperThread udev_thread_;
+  std::mutex udev_thread_mutex_;
+  std::vector<BacklightDev> devices_;
+
+  std::optional<BacklightDev> previous_best_;
+};
+} // namespace waybar::modules

meson.build

@@ -55,6 +55,7 @@ sigcpp = dependency('sigc++-2.0')
 libnl = dependency('libnl-3.0', required: get_option('libnl'))
 libnlgen = dependency('libnl-genl-3.0', required: get_option('libnl'))
 libpulse = dependency('libpulse', required: get_option('pulseaudio'))
+libudev = dependency('libudev')
 
 src_files = files(
     'src/factory.cpp',
@@ -64,6 +65,7 @@ src_files = files(
     'src/modules/clock.cpp',
     'src/modules/custom.cpp',
     'src/modules/cpu.cpp',
+    'src/modules/backlight.cpp',
     'src/main.cpp',
     'src/bar.cpp',
     'src/client.cpp'
@@ -119,7 +121,8 @@ executable(
         giounix,
         libnl,
         libnlgen,
-        libpulse
+        libpulse,
+        libudev
     ],
     include_directories: [include_directories('include')],
     install: true,

resources/config

@@ -6,7 +6,7 @@
     // Choose the order of the modules
     "modules-left": ["sway/workspaces", "sway/mode", "custom/spotify"],
     "modules-center": ["sway/window"],
-    "modules-right": ["pulseaudio", "network", "cpu", "memory", "battery", "battery#bat2", "clock", "tray"],
+    "modules-right": ["pulseaudio", "network", "cpu", "memory", "backlight", "battery", "battery#bat2", "clock", "tray"],
     // Modules configuration
     // "sway/workspaces": {
     //     "disable-scroll": true,
@@ -39,6 +39,11 @@
     "memory": {
         "format": "{}% "
     },
+    "backlight": {
+        // "device": "acpi_video1",
+        "format": "{percent}% {icon}",
+        "format-icons": ["", ""]
+    },
     "battery": {
         "states": {
             // "good": 95,

resources/style.css

@@ -29,7 +29,7 @@ window#waybar {
     border-bottom: 3px solid white;
 }
 
-#clock, #battery, #cpu, #memory, #network, #pulseaudio, #custom-spotify, #tray, #mode {
+#clock, #battery, #cpu, #memory, #backlight, #network, #pulseaudio, #custom-spotify, #tray, #mode {
     padding: 0 10px;
     margin: 0 5px;
 }
@@ -74,6 +74,10 @@ window#waybar {
     background: #9b59b6;
 }
 
+#backlight {
+    background: #90b1b1;
+}
+
 #network {
     background: #2980b9;
 }

src/factory.cpp

@@ -48,6 +48,9 @@ waybar::IModule* waybar::Factory::makeModule(const std::string &name) const
       return new waybar::modules::Pulseaudio(id, config_[name]);
     }
     #endif
+    if (ref == "backlight") {
+      return new waybar::modules::Backlight(id, config_[name]);
+    }
     if (ref.compare(0, 7, "custom/") == 0 && ref.size() > 7) {
       return new waybar::modules::Custom(ref.substr(7), config_[name]);
     }

src/modules/backlight.cpp

@@ -0,0 +1,285 @@
+#include "modules/backlight.hpp"
+
+#include <algorithm>
+#include <chrono>
+#include <memory>
+
+#include <libudev.h>
+
+#include <sys/epoll.h>
+#include <unistd.h>
+
+#include <fmt/format.h>
+
+namespace {
+class FileDescriptor {
+public:
+  explicit FileDescriptor(int fd) : fd_(fd) {}
+  FileDescriptor(const FileDescriptor &other) = delete;
+  FileDescriptor(FileDescriptor &&other) noexcept = delete;
+  FileDescriptor &operator=(const FileDescriptor &other) = delete;
+  FileDescriptor &operator=(FileDescriptor &&other) noexcept = delete;
+  ~FileDescriptor() {
+    if (fd_ != -1) {
+      if (close(fd_) != 0) {
+        fmt::print(stderr, "Failed to close fd: {}\n", errno);
+      }
+    }
+  }
+  int get() const { return fd_; }
+
+private:
+  int fd_;
+};
+
+struct UdevDeleter {
+  void operator()(udev *ptr) { udev_unref(ptr); }
+};
+
+struct UdevDeviceDeleter {
+  void operator()(udev_device *ptr) { udev_device_unref(ptr); }
+};
+
+struct UdevEnumerateDeleter {
+  void operator()(udev_enumerate *ptr) { udev_enumerate_unref(ptr); }
+};
+
+struct UdevMonitorDeleter {
+  void operator()(udev_monitor *ptr) { udev_monitor_unref(ptr); }
+};
+
+void check_eq(int rc, int expected, const char *message = "eq, rc was: ") {
+  if (rc != expected) {
+    throw std::runtime_error(fmt::format(message, rc));
+  }
+}
+
+void check_neq(int rc, int bad_rc, const char *message = "neq, rc was: ") {
+  if (rc == bad_rc) {
+    throw std::runtime_error(fmt::format(message, rc));
+  }
+}
+
+void check0(int rc, const char *message = "rc wasn't 0") {
+  check_eq(rc, 0, message);
+}
+
+void check_gte(int rc, int gte, const char *message = "rc was: ") {
+  if (rc < gte) {
+    throw std::runtime_error(fmt::format(message, rc));
+  }
+}
+
+void check_nn(const void *ptr, const char *message = "ptr was null") {
+  if (ptr == nullptr) {
+    throw std::runtime_error(message);
+  }
+}
+} // namespace
+
+waybar::modules::Backlight::BacklightDev::BacklightDev(std::string name,
+                                                       int actual, int max)
+    : name_(std::move(name)), actual_(actual), max_(max) {}
+
+std::string_view waybar::modules::Backlight::BacklightDev::name() const {
+  return name_;
+}
+
+int waybar::modules::Backlight::BacklightDev::get_actual() const {
+  return actual_;
+}
+
+void waybar::modules::Backlight::BacklightDev::set_actual(int actual) {
+  actual_ = actual;
+}
+
+int waybar::modules::Backlight::BacklightDev::get_max() const { return max_; }
+
+void waybar::modules::Backlight::BacklightDev::set_max(int max) { max_ = max; }
+
+waybar::modules::Backlight::Backlight(const std::string &name,
+                                      const Json::Value &config)
+    : ALabel(config, "{}", 2), name_(name),
+      preferred_device_(
+          config["device"].isString() ? config["device"].asString() : "") {
+  label_.set_name("backlight");
+
+  udev_thread_ = [this] {
+    std::unique_ptr<udev, UdevDeleter> udev{udev_new()};
+    check_nn(udev.get(), "Udev new failed");
+
+    std::unique_ptr<udev_monitor, UdevMonitorDeleter> mon{
+        udev_monitor_new_from_netlink(udev.get(), "udev")};
+    check_nn(mon.get(), "udev monitor new failed");
+    check_gte(udev_monitor_filter_add_match_subsystem_devtype(
+                  mon.get(), "backlight", nullptr),
+              0, "udev failed to add monitor filter: ");
+    udev_monitor_enable_receiving(mon.get());
+
+    auto udev_fd = udev_monitor_get_fd(mon.get());
+
+    auto epoll_fd = FileDescriptor{epoll_create1(0)};
+    check_neq(epoll_fd.get(), -1, "epoll init failed: ");
+    epoll_event ctl_event;
+    ctl_event.events = EPOLLIN;
+    ctl_event.data.fd = udev_fd;
+
+    check0(
+        epoll_ctl(epoll_fd.get(), EPOLL_CTL_ADD, ctl_event.data.fd, &ctl_event),
+        "epoll_ctl failed: {}");
+    epoll_event events[EPOLL_MAX_EVENTS];
+
+    // Get initial state
+    {
+      decltype(devices_) devices;
+      {
+        std::scoped_lock<std::mutex> lock(udev_thread_mutex_);
+        devices = devices_;
+      }
+      enumerate_devices(devices.begin(), devices.end(),
+                        std::back_inserter(devices), udev.get());
+      {
+        std::scoped_lock<std::mutex> lock(udev_thread_mutex_);
+        devices_ = devices;
+      }
+      dp.emit();
+    }
+
+    while (udev_thread_.isRunning()) {
+      const int event_count =
+          epoll_wait(epoll_fd.get(), events, EPOLL_MAX_EVENTS,
+                     std::chrono::milliseconds{interval_}.count());
+      decltype(devices_) devices;
+      {
+        std::scoped_lock<std::mutex> lock(udev_thread_mutex_);
+        devices = devices_;
+      }
+      for (int i = 0; i < event_count; ++i) {
+        const auto &event = events[i];
+        check_eq(event.data.fd, udev_fd, "unexpected udev fd");
+        std::unique_ptr<udev_device, UdevDeviceDeleter> dev{
+            udev_monitor_receive_device(mon.get())};
+        check_nn(dev.get(), "epoll dev was null");
+        upsert_device(devices.begin(), devices.end(),
+                      std::back_inserter(devices), dev.get());
+      }
+
+      // Refresh state if timed out
+      if (event_count == 0) {
+        enumerate_devices(devices.begin(), devices.end(),
+                          std::back_inserter(devices), udev.get());
+      }
+      {
+        std::scoped_lock<std::mutex> lock(udev_thread_mutex_);
+        devices_ = devices;
+      }
+      dp.emit();
+    }
+  };
+}
+
+waybar::modules::Backlight::~Backlight() = default;
+
+auto waybar::modules::Backlight::update() -> void {
+  decltype(devices_) devices;
+  {
+    std::scoped_lock<std::mutex> lock(udev_thread_mutex_);
+    devices = devices_;
+  }
+
+  std::string markup_fmt;
+  if (config_["format"].isString()) {
+    markup_fmt = config_["format"].asString();
+  }
+
+  if (markup_fmt.empty()) {
+    markup_fmt = "{percent}%";
+  }
+
+  const auto best =
+      best_device(devices.cbegin(), devices.cend(), preferred_device_);
+  if (best != nullptr) {
+    if (previous_best_.has_value() && previous_best_.value() == *best) {
+      return;
+    }
+    const auto percent =
+        best->get_max() == 0 ? 100 : best->get_actual() * 100 / best->get_max();
+    label_.set_markup(fmt::format(markup_fmt,
+                                  fmt::arg("percent", std::to_string(percent)),
+                                  fmt::arg("icon", getIcon(percent))));
+  } else {
+    if (!previous_best_.has_value()) {
+      return;
+    }
+    label_.set_markup("");
+  }
+  previous_best_ = best == nullptr ? std::nullopt : std::optional{*best};
+}
+
+template <class ForwardIt>
+const waybar::modules::Backlight::BacklightDev *
+waybar::modules::Backlight::best_device(ForwardIt first, ForwardIt last,
+                                        std::string_view preferred_device) {
+  const auto found =
+      std::find_if(first, last, [preferred_device](const auto &dev) {
+        return dev.name() == preferred_device;
+      });
+  if (found != last) {
+    return &(*found);
+  }
+
+  const auto max =
+      std::max_element(first, last, [](const auto &l, const auto &r) {
+        return l.get_max() < r.get_max();
+      });
+
+  return max == last ? nullptr : &(*max);
+}
+
+template <class ForwardIt, class Inserter>
+void waybar::modules::Backlight::upsert_device(ForwardIt first, ForwardIt last,
+                                               Inserter inserter,
+                                               udev_device *dev) {
+  const char *name = udev_device_get_sysname(dev);
+  check_nn(name);
+
+  const char *actual = udev_device_get_sysattr_value(dev, "actual_brightness");
+  check_nn(actual);
+  const int actual_int = std::stoi(actual);
+
+  const char *max = udev_device_get_sysattr_value(dev, "max_brightness");
+  check_nn(max);
+  const int max_int = std::stoi(max);
+
+  auto found = std::find_if(first, last, [name](const auto &device) {
+    return device.name() == name;
+  });
+  if (found != last) {
+    found->set_actual(actual_int);
+    found->set_max(max_int);
+  } else {
+    *inserter = BacklightDev{name, actual_int, max_int};
+    ++inserter;
+  }
+}
+
+template <class ForwardIt, class Inserter>
+void waybar::modules::Backlight::enumerate_devices(ForwardIt first,
+                                                   ForwardIt last,
+                                                   Inserter inserter,
+                                                   udev *udev) {
+  std::unique_ptr<udev_enumerate, UdevEnumerateDeleter> enumerate{
+      udev_enumerate_new(udev)};
+  udev_enumerate_add_match_subsystem(enumerate.get(), "backlight");
+  udev_enumerate_scan_devices(enumerate.get());
+  udev_list_entry *enum_devices =
+      udev_enumerate_get_list_entry(enumerate.get());
+  udev_list_entry *dev_list_entry;
+  udev_list_entry_foreach(dev_list_entry, enum_devices) {
+    const char *path = udev_list_entry_get_name(dev_list_entry);
+    std::unique_ptr<udev_device, UdevDeviceDeleter> dev{
+        udev_device_new_from_syspath(udev, path)};
+    check_nn(dev.get(), "dev new failed");
+    upsert_device(first, last, inserter, dev.get());
+  }
+}