perf(memory): eliminate deep copies in range-based for loops and lambdas

This commit addresses memory churn caused by implicit deep copies during traversal and allocation of complex structures:

- Replaced pass-by-value 'Json::Value' in std::ranges and range-based for loops with 'const auto&' or 'const Json::Value&' in Hyprland modules, preventing large JSON tree duplications on every update.

- Fixed implicit string and pair copies in UPower and CPU Frequency loops by converting 'auto' to 'const auto&' where possible.

- Added 'std::vector::reserve' calls before 'push_back' loops in MPRIS, Niri, and CFFI modules to prevent exponential vector reallocation during initialization.

Signed-off-by: Austin Horstman <khaneliman12@gmail.com>

src/modules/cffi.cpp

@@ -71,6 +71,7 @@ CFFI::CFFI(const std::string& name, const std::string& id, const Json::Value& co
 
   // Prepare config_entries array
   std::vector<ffi::wbcffi_config_entry> config_entries;
+  config_entries.reserve(keys.size());
   for (size_t i = 0; i < keys.size(); i++) {
     config_entries.push_back({keys[i].c_str(), config_entries_stringstor[i].c_str()});
   }

src/modules/cpu_frequency/linux.cpp

@@ -26,7 +26,7 @@ std::vector<float> waybar::modules::CpuFrequency::parseCpuFrequencies() {
     if (std::filesystem::exists(cpufreq_dir)) {
       std::vector<std::string> frequency_files = {"/cpuinfo_min_freq", "/cpuinfo_max_freq"};
       for (auto& p : std::filesystem::directory_iterator(cpufreq_dir)) {
-        for (auto freq_file : frequency_files) {
+        for (const auto& freq_file : frequency_files) {
           std::string freq_file_path = p.path().string() + freq_file;
           if (std::filesystem::exists(freq_file_path)) {
             std::string freq_value;

src/modules/hyprland/window.cpp

@@ -124,7 +124,7 @@ auto Window::getActiveWorkspace(const std::string& monitorName) -> Workspace {
   const auto monitors = IPC::inst().getSocket1JsonReply("monitors");
   if (monitors.isArray()) {
     auto monitor = std::ranges::find_if(
-        monitors, [&](Json::Value monitor) { return monitor["name"] == monitorName; });
+        monitors, [&](const Json::Value& monitor) { return monitor["name"] == monitorName; });
     if (monitor == std::end(monitors)) {
       spdlog::warn("Monitor not found: {}", monitorName);
       return Workspace{
@@ -139,7 +139,7 @@ auto Window::getActiveWorkspace(const std::string& monitorName) -> Workspace {
     const auto workspaces = IPC::inst().getSocket1JsonReply("workspaces");
     if (workspaces.isArray()) {
       auto workspace = std::ranges::find_if(
-          workspaces, [&](Json::Value workspace) { return workspace["id"] == id; });
+          workspaces, [&](const Json::Value& workspace) { return workspace["id"] == id; });
       if (workspace == std::end(workspaces)) {
         spdlog::warn("No workspace with id {}", id);
         return Workspace{
@@ -190,7 +190,7 @@ void Window::queryActiveWorkspace() {
     const auto clients = m_ipc.getSocket1JsonReply("clients");
     if (clients.isArray()) {
       auto activeWindow = std::ranges::find_if(
-          clients, [&](Json::Value window) { return window["address"] == workspace_.last_window; });
+          clients, [&](const Json::Value& window) { return window["address"] == workspace_.last_window; });
 
       if (activeWindow == std::end(clients)) {
         focused_ = false;
@@ -200,19 +200,19 @@ void Window::queryActiveWorkspace() {
       windowData_ = WindowData::parse(*activeWindow);
       updateAppIconName(windowData_.class_name, windowData_.initial_class_name);
       std::vector<Json::Value> workspaceWindows;
-      std::ranges::copy_if(clients, std::back_inserter(workspaceWindows), [&](Json::Value window) {
+      std::ranges::copy_if(clients, std::back_inserter(workspaceWindows), [&](const Json::Value& window) {
         return window["workspace"]["id"] == workspace_.id && window["mapped"].asBool();
       });
-      swallowing_ = std::ranges::any_of(workspaceWindows, [&](Json::Value window) {
+      swallowing_ = std::ranges::any_of(workspaceWindows, [&](const Json::Value& window) {
         return !window["swallowing"].isNull() && window["swallowing"].asString() != "0x0";
       });
       std::vector<Json::Value> visibleWindows;
       std::ranges::copy_if(workspaceWindows, std::back_inserter(visibleWindows),
-                           [&](Json::Value window) { return !window["hidden"].asBool(); });
+                           [&](const Json::Value& window) { return !window["hidden"].asBool(); });
       solo_ = 1 == std::count_if(visibleWindows.begin(), visibleWindows.end(),
-                                 [&](Json::Value window) { return !window["floating"].asBool(); });
+                                 [&](const Json::Value& window) { return !window["floating"].asBool(); });
       allFloating_ = std::ranges::all_of(
-          visibleWindows, [&](Json::Value window) { return window["floating"].asBool(); });
+          visibleWindows, [&](const Json::Value& window) { return window["floating"].asBool(); });
       fullscreen_ = windowData_.fullscreen;
 
       // Fullscreen windows look like they are solo

src/modules/hyprland/windowcount.cpp

@@ -79,7 +79,7 @@ auto WindowCount::getActiveWorkspace(const std::string& monitorName) -> Workspac
   const auto monitors = m_ipc.getSocket1JsonReply("monitors");
   if (monitors.isArray()) {
     auto monitor = std::ranges::find_if(
-        monitors, [&](Json::Value monitor) { return monitor["name"] == monitorName; });
+        monitors, [&](const Json::Value& monitor) { return monitor["name"] == monitorName; });
     if (monitor == std::end(monitors)) {
       spdlog::warn("Monitor not found: {}", monitorName);
       return Workspace{
@@ -93,7 +93,7 @@ auto WindowCount::getActiveWorkspace(const std::string& monitorName) -> Workspac
     const auto workspaces = m_ipc.getSocket1JsonReply("workspaces");
     if (workspaces.isArray()) {
       auto workspace = std::ranges::find_if(
-          workspaces, [&](Json::Value workspace) { return workspace["id"] == id; });
+          workspaces, [&](const Json::Value& workspace) { return workspace["id"] == id; });
       if (workspace == std::end(workspaces)) {
         spdlog::warn("No workspace with id {}", id);
         return Workspace{

src/modules/hyprland/workspace.cpp

@@ -96,7 +96,7 @@ bool Workspace::handleClicked(GdkEventButton* bt) const {
 
 void Workspace::initializeWindowMap(const Json::Value& clients_data) {
   m_windowMap.clear();
-  for (auto client : clients_data) {
+  for (const auto& client : clients_data) {
     if (client["workspace"]["id"].asInt() == id()) {
       insertWindow({client});
     }

src/modules/hyprland/workspaces.cpp

@@ -197,7 +197,7 @@ void Workspaces::initializeWorkspaces() {
   auto const workspacesJson = m_ipc.getSocket1JsonReply("workspaces");
   auto const clientsJson = m_ipc.getSocket1JsonReply("clients");
 
-  for (Json::Value workspaceJson : workspacesJson) {
+  for (const auto& workspaceJson : workspacesJson) {
     std::string workspaceName = workspaceJson["name"].asString();
     if ((allOutputs() || m_bar.output->name == workspaceJson["monitor"].asString()) &&
         (!workspaceName.starts_with("special") || showSpecial()) &&
@@ -401,7 +401,7 @@ void Workspaces::onWorkspaceCreated(std::string const& payload, Json::Value cons
   auto const workspaceRules = m_ipc.getSocket1JsonReply("workspacerules");
   auto const workspacesJson = m_ipc.getSocket1JsonReply("workspaces");
 
-  for (Json::Value workspaceJson : workspacesJson) {
+  for (auto workspaceJson : workspacesJson) {
     const auto currentId = workspaceJson["id"].asInt();
     if (currentId == *workspaceId) {
       std::string workspaceName = workspaceJson["name"].asString();
@@ -1004,7 +1004,7 @@ void Workspaces::setUrgentWorkspace(std::string const& windowaddress) {
   const Json::Value clientsJson = m_ipc.getSocket1JsonReply("clients");
   int workspaceId = -1;
 
-  for (Json::Value clientJson : clientsJson) {
+  for (const auto& clientJson : clientsJson) {
     if (clientJson["address"].asString().ends_with(windowaddress)) {
       workspaceId = clientJson["workspace"]["id"].asInt();
       break;

src/modules/mpris/mpris.cpp

@@ -109,6 +109,7 @@ Mpris::Mpris(const std::string& id, const Json::Value& config)
     player_ = config_["player"].asString();
   }
   if (config_["ignored-players"].isArray()) {
+    ignored_players_.reserve(config_["ignored-players"].size());
     for (const auto& item : config_["ignored-players"]) {
       if (item.isString()) {
         ignored_players_.push_back(item.asString());

src/modules/niri/language.cpp

@@ -32,6 +32,7 @@ void Language::updateFromIPC() {
   auto ipcLock = gIPC->lockData();
 
   layouts_.clear();
+  layouts_.reserve(gIPC->keyboardLayoutNames().size());
   for (const auto& fullName : gIPC->keyboardLayoutNames()) layouts_.push_back(getLayout(fullName));
 
   current_idx_ = gIPC->keyboardLayoutCurrent();