fix(bar): reduce keyboard layout CPU usage

src/compositors/hyprland/hyprland_keyboard_backend.cpp

@@ -3,6 +3,7 @@
 #include "core/process.h"
 #include "util/string_utils.h"
 
+#include <chrono>
 #include <cstdlib>
 #include <json.hpp>
 #include <sys/wait.h>
@@ -11,6 +12,21 @@
 
 namespace {
 
+  constexpr auto kCurrentLayoutCacheTtl = std::chrono::seconds(1);
+
+  struct CurrentLayoutCache {
+    std::optional<std::string> value;
+    std::chrono::steady_clock::time_point fetchedAt{};
+    bool valid = false;
+  };
+
+  CurrentLayoutCache& currentLayoutCache() {
+    static CurrentLayoutCache cache;
+    return cache;
+  }
+
+  void invalidateCurrentLayoutCache() { currentLayoutCache() = CurrentLayoutCache{}; }
+
   [[nodiscard]] std::optional<std::string> runAndCapture(const std::vector<std::string>& args) {
     if (args.empty() || args.front().empty()) {
       return std::nullopt;
@@ -75,7 +91,11 @@ bool HyprlandKeyboardBackend::cycleLayout() const {
   if (!m_enabled) {
     return false;
   }
-  return process::runSync({"hyprctl", "switchxkblayout", "all", "next"});
+  const bool ok = process::runSync({"hyprctl", "switchxkblayout", "all", "next"});
+  if (ok) {
+    invalidateCurrentLayoutCache();
+  }
+  return ok;
 }
 
 std::optional<KeyboardLayoutState> HyprlandKeyboardBackend::layoutState() const {
@@ -91,16 +111,29 @@ std::optional<std::string> HyprlandKeyboardBackend::currentLayoutName() const {
     return std::nullopt;
   }
 
+  const auto now = std::chrono::steady_clock::now();
+  auto& cache = currentLayoutCache();
+  if (cache.valid && now - cache.fetchedAt < kCurrentLayoutCacheTtl) {
+    return cache.value;
+  }
+
+  auto finish = [&](std::optional<std::string> value) {
+    cache.value = std::move(value);
+    cache.fetchedAt = now;
+    cache.valid = true;
+    return cache.value;
+  };
+
   const auto payload = runAndCapture({"hyprctl", "devices", "-j"});
   if (!payload.has_value() || payload->empty()) {
-    return std::nullopt;
+    return finish(std::nullopt);
   }
 
   try {
     const auto json = nlohmann::json::parse(*payload);
     const auto keyboardsIt = json.find("keyboards");
     if (keyboardsIt == json.end() || !keyboardsIt->is_array()) {
-      return std::nullopt;
+      return finish(std::nullopt);
     }
     for (const auto& keyboard : *keyboardsIt) {
       if (!keyboard.is_object()) {
@@ -111,12 +144,12 @@ std::optional<std::string> HyprlandKeyboardBackend::currentLayoutName() const {
       }
       const std::string layout = keyboard.value("active_keymap", "");
       if (!layout.empty() && layout != "error") {
-        return layout;
+        return finish(layout);
       }
     }
   } catch (const nlohmann::json::exception&) {
-    return std::nullopt;
+    return finish(std::nullopt);
   }
 
-  return std::nullopt;
+  return finish(std::nullopt);
 }

src/compositors/sway/sway_keyboard_backend.cpp

@@ -3,6 +3,7 @@
 #include "core/process.h"
 #include "util/string_utils.h"
 
+#include <chrono>
 #include <cstdlib>
 #include <json.hpp>
 #include <sys/wait.h>
@@ -11,6 +12,21 @@
 
 namespace {
 
+  constexpr auto kCurrentLayoutCacheTtl = std::chrono::seconds(1);
+
+  struct CurrentLayoutCache {
+    std::optional<std::string> value;
+    std::chrono::steady_clock::time_point fetchedAt{};
+    bool valid = false;
+  };
+
+  CurrentLayoutCache& currentLayoutCache() {
+    static CurrentLayoutCache cache;
+    return cache;
+  }
+
+  void invalidateCurrentLayoutCache() { currentLayoutCache() = CurrentLayoutCache{}; }
+
   [[nodiscard]] std::optional<std::string> runAndCapture(const std::vector<std::string>& args) {
     if (args.empty() || args.front().empty()) {
       return std::nullopt;
@@ -75,7 +91,11 @@ bool SwayKeyboardBackend::cycleLayout() const {
   if (!isAvailable()) {
     return false;
   }
-  return process::runSync({m_msgCommand, "input", "type:keyboard", "xkb_switch_layout", "next"});
+  const bool ok = process::runSync({m_msgCommand, "input", "type:keyboard", "xkb_switch_layout", "next"});
+  if (ok) {
+    invalidateCurrentLayoutCache();
+  }
+  return ok;
 }
 
 std::optional<KeyboardLayoutState> SwayKeyboardBackend::layoutState() const {
@@ -91,15 +111,28 @@ std::optional<std::string> SwayKeyboardBackend::currentLayoutName() const {
     return std::nullopt;
   }
 
+  const auto now = std::chrono::steady_clock::now();
+  auto& cache = currentLayoutCache();
+  if (cache.valid && now - cache.fetchedAt < kCurrentLayoutCacheTtl) {
+    return cache.value;
+  }
+
+  auto finish = [&](std::optional<std::string> value) {
+    cache.value = std::move(value);
+    cache.fetchedAt = now;
+    cache.valid = true;
+    return cache.value;
+  };
+
   const auto payload = runAndCapture({m_msgCommand, "-t", "get_inputs", "--raw"});
   if (!payload.has_value() || payload->empty()) {
-    return std::nullopt;
+    return finish(std::nullopt);
   }
 
   try {
     const auto json = nlohmann::json::parse(*payload);
     if (!json.is_array()) {
-      return std::nullopt;
+      return finish(std::nullopt);
     }
     for (const auto& input : json) {
       if (!input.is_object()) {
@@ -110,12 +143,12 @@ std::optional<std::string> SwayKeyboardBackend::currentLayoutName() const {
       }
       const std::string layout = input.value("xkb_active_layout_name", "");
       if (!layout.empty()) {
-        return layout;
+        return finish(layout);
       }
     }
   } catch (const nlohmann::json::exception&) {
-    return std::nullopt;
+    return finish(std::nullopt);
   }
 
-  return std::nullopt;
+  return finish(std::nullopt);
 }

src/shell/bar/widgets/keyboard_layout_widget.cpp

@@ -23,7 +23,6 @@ namespace {
   constexpr Logger kLog("keyboard_layout_widget");
   constexpr auto kRefreshTickInterval = std::chrono::milliseconds(40);
   constexpr int kRefreshBurstAttempts = 8;
-  constexpr auto kIdleProbeInterval = std::chrono::milliseconds(350);
   constexpr std::string_view kUnknownLabel = "--";
   constexpr std::string_view kVerticalStableLabel = "WWW";
 
@@ -327,14 +326,8 @@ void KeyboardLayoutWidget::create() {
 
   setRoot(std::move(area));
 
-  // Keyboard layout changes are not event-pushed for all compositor backends.
-  // Keep a low-frequency idle probe so passive switches are reflected promptly.
-  m_idleRefreshTimer.startRepeating(kIdleProbeInterval, [this]() {
-    if (m_refreshAttemptsRemaining > 0) {
-      return;
-    }
-    requestUpdate();
-  });
+  // The bar's normal second tick refreshes passive compositor-side layout changes.
+  // Click-initiated switches still use the short burst timer below for responsive feedback.
 }
 
 void KeyboardLayoutWidget::doLayout(Renderer& renderer, float containerWidth, float containerHeight) {

src/shell/bar/widgets/keyboard_layout_widget.h

@@ -44,7 +44,6 @@ private:
   bool m_clickArmed = false;
   int m_refreshAttemptsRemaining = 0;
   Timer m_refreshTimer;
-  Timer m_idleRefreshTimer;
   bool m_isVertical = false;
   bool m_lastVertical = false;
 };