Implement shared execs for custom modules

For more complicated configurations with several actions activated
through clicks on various connected modules, it is currently necessary
to have each of those connected modules exec their own subprocess to
produce the wanted output. This is problematic because it greatly
increases CPU usage.

Implement a new configuration option for bars, "custom-execs", which
contains an array of subprocess specifications ("exec", "exec_if",
"interval", "restart-interval"). The bar runs each of these executables
and reads their output. The output is in the form of a JSON object with
module names as keys and either strings (for "raw" type output) or
objects (for "json" type output) as values. These values are forwarded
to the custom modules named by the keys.

include/bar.hpp

@@ -9,6 +9,9 @@
 #include <json/json.h>
 
 #include "AModule.hpp"
+#include "modules/custom.hpp"
+#include "util/json.hpp"
+#include "util/worker_thread.hpp"
 #include "xdg-output-unstable-v1-client-protocol.h"
 
 namespace waybar {
@@ -76,6 +79,7 @@ class Bar {
   void getModules(const Factory &, const std::string &);
   void setupAltFormatKeyForModule(const std::string &module_name);
   void setupAltFormatKeyForModuleList(const char *module_list_name);
+  void customExecOutputCallback(std::string output);
 
   std::unique_ptr<BarSurface>                   surface_impl_;
   bar_layer                                     layer_;
@@ -86,6 +90,10 @@ 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_;
+  waybar::util::JsonParser                      parser_;
+  // Contains pointers to modules in modules_left_, etc.
+  std::map<std::string, waybar::modules::Custom *>         custom_modules_;
+  std::vector<std::unique_ptr<waybar::util::WorkerThread>> custom_threads_;
 };
 
 }  // namespace waybar

include/modules/custom.hpp

@@ -3,7 +3,9 @@
 #include <fmt/format.h>
 
 #include <csignal>
+#include <mutex>
 #include <string>
+#include <variant>
 
 #include "ALabel.hpp"
 #include "util/command.hpp"
@@ -15,6 +17,7 @@ namespace waybar::modules {
 class Custom : public ALabel {
  public:
   Custom(const std::string&, const std::string&, const Json::Value&);
+  void injectOutput(Json::Value);
   auto update() -> void;
   void refresh(int /*signal*/);
 
@@ -23,6 +26,7 @@ class Custom : public ALabel {
   void workerOutputCallback(std::string);
   void parseOutputRaw(const std::string&);
   void parseOutputJson(const std::string&);
+  void handleOutputJson(const Json::Value&);
   void handleEvent();
   bool handleScroll(GdkEventScroll* e);
   bool handleToggle(GdkEventButton* const& e);
@@ -33,9 +37,12 @@ class Custom : public ALabel {
   std::string              tooltip_;
   std::vector<std::string> class_;
   int                      percentage_;
-  util::command::res       output_;
+  // Worker exit code, worker raw output, or injected JSON.
+  // Injected JSON is string for raw output, object for JSON output.
+  std::variant<std::monostate, int, std::string, Json::Value> output_;
   util::JsonParser                                            parser_;
-
+  // Protects output_ since it is accessed from many threads.
+  std::mutex                 output_mutex_;
   waybar::util::WorkerThread thread_;
 };
 

src/bar.cpp

@@ -508,6 +508,20 @@ waybar::Bar::Bar(struct waybar_output* w_output, const Json::Value& w_config)
   window.signal_map_event().connect_notify(sigc::mem_fun(*this, &Bar::onMap));
 
   setupWidgets();
+
+  if (config["custom-execs"].isArray()) {
+    Json::ArrayIndex size = config["custom-execs"].size();
+    for (Json::ArrayIndex i = 0; i < size; i++) {
+      custom_threads_.push_back(std::make_unique<waybar::util::WorkerThread>(
+          config["custom-execs"][i],
+          [this](std::string output) { customExecOutputCallback(output); },
+          [this](int exit_code) {
+            // Do nothing. We don't know which modules this was meant for.
+            spdlog::debug("Custom exec exited with code {}", exit_code);
+          }));
+    }
+  }
+
   window.show_all();
 
   if (spdlog::should_log(spdlog::level::debug)) {
@@ -521,6 +535,19 @@ waybar::Bar::Bar(struct waybar_output* w_output, const Json::Value& w_config)
   }
 }
 
+void waybar::Bar::customExecOutputCallback(std::string output) {
+  // parsed is an object with module names as keys and output (string or object) as values.
+  auto parsed = parser_.parse(output);
+  auto end = parsed.end();
+  for (Json::Value::const_iterator module_it = parsed.begin(); module_it != end; ++module_it) {
+    auto it = custom_modules_.find(module_it.name());
+    if (it != custom_modules_.end()) {
+      it->second->injectOutput(*module_it);
+    } else {
+    }
+  }
+}
+
 void waybar::Bar::onMap(GdkEventAny*) {
   /*
    * Obtain a pointer to the custom layer surface for modules that require it (idle_inhibitor).
@@ -612,6 +639,10 @@ void waybar::Bar::getModules(const Factory& factory, const std::string& pos) {
     for (const auto& name : config[pos]) {
       try {
         auto module = factory.makeModule(name.asString());
+        auto custom = dynamic_cast<waybar::modules::Custom*>(module);
+        if (custom != nullptr) {
+          custom_modules_[name.asString()] = custom;
+        }
         if (pos == "modules-left") {
           modules_left_.emplace_back(module);
         }

src/modules/custom.cpp

@@ -13,12 +13,26 @@ waybar::modules::Custom::Custom(const std::string& name, const std::string& id,
 }
 
 void waybar::modules::Custom::workerExitCallback(int exit_code) {
-  output_ = {exit_code, ""};
+  {
+    std::lock_guard<std::mutex> guard(output_mutex_);
+    output_ = exit_code;
+  }
   dp.emit();
 }
 
 void waybar::modules::Custom::workerOutputCallback(std::string output) {
-  output_ = {0, std::move(output)};
+  {
+    std::lock_guard<std::mutex> guard(output_mutex_);
+    output_ = std::move(output);
+  }
+  dp.emit();
+}
+
+void waybar::modules::Custom::injectOutput(Json::Value output) {
+  {
+    std::lock_guard<std::mutex> guard(output_mutex_);
+    output_ = std::move(output);
+  }
   dp.emit();
 }
 
@@ -47,23 +61,52 @@ bool waybar::modules::Custom::handleToggle(GdkEventButton* const& e) {
 }
 
 auto waybar::modules::Custom::update() -> void {
-  // Hide label if output is empty
+  std::variant<std::monostate, int, std::string, Json::Value> output;
-  if ((config_["exec"].isString() || config_["exec-if"].isString()) &&
+  {
-      (output_.out.empty() || output_.exit_code != 0)) {
+    std::lock_guard<std::mutex> guard(output_mutex_);
-    event_box_.hide();
+    output = std::move(output_);
-  } else {
+    output_ = std::monostate();
-    if (config_["return-type"].asString() == "json") {
-      parseOutputJson(output_.out);
-    } else {
-      parseOutputRaw(output_.out);
   }
+
+  // Hide label if output is empty
+  bool hide = config_["exec"].isString() || config_["exec-if"].isString();
+
+  if (std::holds_alternative<std::monostate>(output)) {
+    if (hide) {
+      // No changes since the last update, do nothing.
+      ALabel::update();
+      return;
+    }
+  } else if (std::holds_alternative<int>(output)) {
+    // The exit code is non-zero if we get here, so do nothing to hide the label.
+  } else if (std::holds_alternative<std::string>(output)) {
+    const std::string& s = std::get<std::string>(output);
+    if (!s.empty()) {
+      hide = false;
+      if (config_["return-type"].asString() == "json") {
+        parseOutputJson(s);
+      } else {
+        parseOutputRaw(s);
+      }
+    }
+  } else {
+    hide = false;
+    const Json::Value& value = std::get<Json::Value>(output);
+    if (value.isString()) {
+      parseOutputRaw(value.asString());
+    } else {
+      handleOutputJson(value);
+    }
+  }
+
+  if (!hide) {
     auto str = fmt::format(format_,
                            text_,
                            fmt::arg("alt", alt_),
                            fmt::arg("icon", getIcon(percentage_, alt_)),
                            fmt::arg("percentage", percentage_));
     if (str.empty()) {
-      event_box_.hide();
+      hide = true;
     } else {
       label_.set_markup(str);
       if (tooltipEnabled()) {
@@ -87,6 +130,11 @@ auto waybar::modules::Custom::update() -> void {
       event_box_.show();
     }
   }
+
+  if (hide) {
+    event_box_.hide();
+  }
+
   // Call parent update
   ALabel::update();
 }
@@ -121,29 +169,33 @@ void waybar::modules::Custom::parseOutputJson(const std::string& output_str) {
   class_.clear();
   while (getline(output, line)) {
     auto parsed = parser_.parse(line);
-    if (config_["escape"].isBool() && config_["escape"].asBool()) {
+    handleOutputJson(parsed);
-      text_ = Glib::Markup::escape_text(parsed["text"].asString());
-    } else {
-      text_ = parsed["text"].asString();
-    }
-    if (config_["escape"].isBool() && config_["escape"].asBool()) {
-      alt_ = Glib::Markup::escape_text(parsed["alt"].asString());
-    } else {
-      alt_ = parsed["alt"].asString();
-    }
-    tooltip_ = parsed["tooltip"].asString();
-    if (parsed["class"].isString()) {
-      class_.push_back(parsed["class"].asString());
-    } else if (parsed["class"].isArray()) {
-      for (auto const& c : parsed["class"]) {
-        class_.push_back(c.asString());
-      }
-    }
-    if (!parsed["percentage"].asString().empty() && parsed["percentage"].isUInt()) {
-      percentage_ = parsed["percentage"].asUInt();
-    } else {
-      percentage_ = 0;
-    }
     break;
   }
 }
+
+void waybar::modules::Custom::handleOutputJson(const Json::Value& value) {
+  if (config_["escape"].isBool() && config_["escape"].asBool()) {
+    text_ = Glib::Markup::escape_text(value["text"].asString());
+  } else {
+    text_ = value["text"].asString();
+  }
+  if (config_["escape"].isBool() && config_["escape"].asBool()) {
+    alt_ = Glib::Markup::escape_text(value["alt"].asString());
+  } else {
+    alt_ = value["alt"].asString();
+  }
+  tooltip_ = value["tooltip"].asString();
+  if (value["class"].isString()) {
+    class_.push_back(value["class"].asString());
+  } else if (value["class"].isArray()) {
+    for (auto const& c : value["class"]) {
+      class_.push_back(c.asString());
+    }
+  }
+  if (!value["percentage"].asString().empty() && value["percentage"].isUInt()) {
+    percentage_ = value["percentage"].asUInt();
+  } else {
+    percentage_ = 0;
+  }
+}