fix: Added missing up/down button labels (#935)

## Summary

**What is the goal of this PR?**

In some places, button labels are omitted intentionally because the
button has no purpose in the activity. I noticed a few obvious cases,
like Home > File Transfer and Settings > System > Language, where the up
and down button labels were missing. This change fixes those and all
similar instances I could find.

---

### AI Usage

While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.

Did you use AI tools to help write this code? _**NO**_

lib/GfxRenderer/GfxRenderer.cpp

@@ -74,13 +74,14 @@ void GfxRenderer::drawPixel(const int x, const int y, const bool state) const {
 }
 
 int GfxRenderer::getTextWidth(const int fontId, const char* text, const EpdFontFamily::Style style) const {
-  if (fontMap.count(fontId) == 0) {
+  const auto fontIt = fontMap.find(fontId);
+  if (fontIt == fontMap.end()) {
     LOG_ERR("GFX", "Font %d not found", fontId);
     return 0;
   }
 
   int w = 0, h = 0;
-  fontMap.at(fontId).getTextDimensions(text, &w, &h, style);
+  fontIt->second.getTextDimensions(text, &w, &h, style);
   return w;
 }
 
@@ -100,11 +101,12 @@ void GfxRenderer::drawText(const int fontId, const int x, const int y, const cha
     return;
   }
 
-  if (fontMap.count(fontId) == 0) {
+  const auto fontIt = fontMap.find(fontId);
+  if (fontIt == fontMap.end()) {
     LOG_ERR("GFX", "Font %d not found", fontId);
     return;
   }
-  const auto font = fontMap.at(fontId);
+  const auto& font = fontIt->second;
 
   // no printable characters
   if (!font.hasPrintableChars(text, style)) {
@@ -709,52 +711,58 @@ int GfxRenderer::getScreenHeight() const {
 }
 
 int GfxRenderer::getSpaceWidth(const int fontId) const {
-  if (fontMap.count(fontId) == 0) {
+  const auto fontIt = fontMap.find(fontId);
+  if (fontIt == fontMap.end()) {
     LOG_ERR("GFX", "Font %d not found", fontId);
     return 0;
   }
 
-  return fontMap.at(fontId).getGlyph(' ', EpdFontFamily::REGULAR)->advanceX;
+  return fontIt->second.getGlyph(' ', EpdFontFamily::REGULAR)->advanceX;
 }
 
 int GfxRenderer::getTextAdvanceX(const int fontId, const char* text) const {
-  if (fontMap.count(fontId) == 0) {
+  const auto fontIt = fontMap.find(fontId);
+  if (fontIt == fontMap.end()) {
     LOG_ERR("GFX", "Font %d not found", fontId);
     return 0;
   }
 
   uint32_t cp;
   int width = 0;
+  const auto& font = fontIt->second;
   while ((cp = utf8NextCodepoint(reinterpret_cast<const uint8_t**>(&text)))) {
-    width += fontMap.at(fontId).getGlyph(cp, EpdFontFamily::REGULAR)->advanceX;
+    width += font.getGlyph(cp, EpdFontFamily::REGULAR)->advanceX;
   }
   return width;
 }
 
 int GfxRenderer::getFontAscenderSize(const int fontId) const {
-  if (fontMap.count(fontId) == 0) {
+  const auto fontIt = fontMap.find(fontId);
+  if (fontIt == fontMap.end()) {
     LOG_ERR("GFX", "Font %d not found", fontId);
     return 0;
   }
 
-  return fontMap.at(fontId).getData(EpdFontFamily::REGULAR)->ascender;
+  return fontIt->second.getData(EpdFontFamily::REGULAR)->ascender;
 }
 
 int GfxRenderer::getLineHeight(const int fontId) const {
-  if (fontMap.count(fontId) == 0) {
+  const auto fontIt = fontMap.find(fontId);
+  if (fontIt == fontMap.end()) {
     LOG_ERR("GFX", "Font %d not found", fontId);
     return 0;
   }
 
-  return fontMap.at(fontId).getData(EpdFontFamily::REGULAR)->advanceY;
+  return fontIt->second.getData(EpdFontFamily::REGULAR)->advanceY;
 }
 
 int GfxRenderer::getTextHeight(const int fontId) const {
-  if (fontMap.count(fontId) == 0) {
+  const auto fontIt = fontMap.find(fontId);
+  if (fontIt == fontMap.end()) {
     LOG_ERR("GFX", "Font %d not found", fontId);
     return 0;
   }
-  return fontMap.at(fontId).getData(EpdFontFamily::REGULAR)->ascender;
+  return fontIt->second.getData(EpdFontFamily::REGULAR)->ascender;
 }
 
 void GfxRenderer::drawTextRotated90CW(const int fontId, const int x, const int y, const char* text, const bool black,
@@ -764,11 +772,13 @@ void GfxRenderer::drawTextRotated90CW(const int fontId, const int x, const int y
     return;
   }
 
-  if (fontMap.count(fontId) == 0) {
+  const auto fontIt = fontMap.find(fontId);
+  if (fontIt == fontMap.end()) {
     LOG_ERR("GFX", "Font %d not found", fontId);
     return;
   }
-  const auto font = fontMap.at(fontId);
+
+  const auto& font = fontIt->second;
 
   // No printable characters
   if (!font.hasPrintableChars(text, style)) {

lib/hal/HalGPIO.cpp

@@ -1,11 +1,9 @@
 #include <HalGPIO.h>
 #include <SPI.h>
-#include <esp_sleep.h>
 
 void HalGPIO::begin() {
   inputMgr.begin();
   SPI.begin(EPD_SCLK, SPI_MISO, EPD_MOSI, EPD_CS);
-  pinMode(BAT_GPIO0, INPUT);
   pinMode(UART0_RXD, INPUT);
 }
 
@@ -23,23 +21,6 @@ bool HalGPIO::wasAnyReleased() const { return inputMgr.wasAnyReleased(); }
 
 unsigned long HalGPIO::getHeldTime() const { return inputMgr.getHeldTime(); }
 
-void HalGPIO::startDeepSleep() {
-  // Ensure that the power button has been released to avoid immediately turning back on if you're holding it
-  while (inputMgr.isPressed(BTN_POWER)) {
-    delay(50);
-    inputMgr.update();
-  }
-  // Arm the wakeup trigger *after* the button is released
-  esp_deep_sleep_enable_gpio_wakeup(1ULL << InputManager::POWER_BUTTON_PIN, ESP_GPIO_WAKEUP_GPIO_LOW);
-  // Enter Deep Sleep
-  esp_deep_sleep_start();
-}
-
-int HalGPIO::getBatteryPercentage() const {
-  static const BatteryMonitor battery = BatteryMonitor(BAT_GPIO0);
-  return battery.readPercentage();
-}
-
 bool HalGPIO::isUsbConnected() const {
   // U0RXD/GPIO20 reads HIGH when USB is connected
   return digitalRead(UART0_RXD) == HIGH;

lib/hal/HalGPIO.h

@@ -38,12 +38,6 @@ class HalGPIO {
   bool wasAnyReleased() const;
   unsigned long getHeldTime() const;
 
-  // Setup wake up GPIO and enter deep sleep
-  void startDeepSleep();
-
-  // Get battery percentage (range 0-100)
-  int getBatteryPercentage() const;
-
   // Check if USB is connected
   bool isUsbConnected() const;
 

lib/hal/HalPowerManager.cpp

@@ -0,0 +1,95 @@
+#include "HalPowerManager.h"
+
+#include <Logging.h>
+#include <WiFi.h>
+#include <esp_sleep.h>
+
+#include <cassert>
+
+#include "HalGPIO.h"
+
+HalPowerManager powerManager;  // Singleton instance
+
+void HalPowerManager::begin() {
+  pinMode(BAT_GPIO0, INPUT);
+  normalFreq = getCpuFrequencyMhz();
+  modeMutex = xSemaphoreCreateMutex();
+  assert(modeMutex != nullptr);
+}
+
+void HalPowerManager::setPowerSaving(bool enabled) {
+  if (normalFreq <= 0) {
+    return;  // invalid state
+  }
+
+  auto wifiMode = WiFi.getMode();
+  if (wifiMode != WIFI_MODE_NULL) {
+    // Wifi is active, force disabling power saving
+    enabled = false;
+  }
+
+  // Note: We don't use mutex here to avoid too much overhead,
+  // it's not very important if we read a slightly stale value for currentLockMode
+  const LockMode mode = currentLockMode;
+
+  if (mode == None && enabled && !isLowPower) {
+    LOG_DBG("PWR", "Going to low-power mode");
+    if (!setCpuFrequencyMhz(LOW_POWER_FREQ)) {
+      LOG_DBG("PWR", "Failed to set CPU frequency = %d MHz", LOW_POWER_FREQ);
+      return;
+    }
+    isLowPower = true;
+
+  } else if ((!enabled || mode != None) && isLowPower) {
+    LOG_DBG("PWR", "Restoring normal CPU frequency");
+    if (!setCpuFrequencyMhz(normalFreq)) {
+      LOG_DBG("PWR", "Failed to set CPU frequency = %d MHz", normalFreq);
+      return;
+    }
+    isLowPower = false;
+  }
+
+  // Otherwise, no change needed
+}
+
+void HalPowerManager::startDeepSleep(HalGPIO& gpio) const {
+  // Ensure that the power button has been released to avoid immediately turning back on if you're holding it
+  while (gpio.isPressed(HalGPIO::BTN_POWER)) {
+    delay(50);
+    gpio.update();
+  }
+  // Arm the wakeup trigger *after* the button is released
+  esp_deep_sleep_enable_gpio_wakeup(1ULL << InputManager::POWER_BUTTON_PIN, ESP_GPIO_WAKEUP_GPIO_LOW);
+  // Enter Deep Sleep
+  esp_deep_sleep_start();
+}
+
+int HalPowerManager::getBatteryPercentage() const {
+  static const BatteryMonitor battery = BatteryMonitor(BAT_GPIO0);
+  return battery.readPercentage();
+}
+
+HalPowerManager::Lock::Lock() {
+  xSemaphoreTake(powerManager.modeMutex, portMAX_DELAY);
+  // Current limitation: only one lock at a time
+  if (powerManager.currentLockMode != None) {
+    LOG_ERR("PWR", "Lock already held, ignore");
+    valid = false;
+  } else {
+    powerManager.currentLockMode = NormalSpeed;
+    valid = true;
+  }
+  xSemaphoreGive(powerManager.modeMutex);
+  if (valid) {
+    // Immediately restore normal CPU frequency if currently in low-power mode
+    powerManager.setPowerSaving(false);
+  }
+}
+
+HalPowerManager::Lock::~Lock() {
+  xSemaphoreTake(powerManager.modeMutex, portMAX_DELAY);
+  if (valid) {
+    powerManager.currentLockMode = None;
+  }
+  xSemaphoreGive(powerManager.modeMutex);
+}

lib/hal/HalPowerManager.h

@@ -0,0 +1,56 @@
+#pragma once
+
+#include <Arduino.h>
+#include <InputManager.h>
+#include <Logging.h>
+#include <freertos/semphr.h>
+
+#include <cassert>
+
+#include "HalGPIO.h"
+
+class HalPowerManager;
+extern HalPowerManager powerManager;  // Singleton
+
+class HalPowerManager {
+  int normalFreq = 0;  // MHz
+  bool isLowPower = false;
+
+  enum LockMode { None, NormalSpeed };
+  LockMode currentLockMode = None;
+  SemaphoreHandle_t modeMutex = nullptr;  // Protect access to currentLockMode
+
+ public:
+  static constexpr int LOW_POWER_FREQ = 10;                    // MHz
+  static constexpr unsigned long IDLE_POWER_SAVING_MS = 3000;  // ms
+
+  void begin();
+
+  // Control CPU frequency for power saving
+  void setPowerSaving(bool enabled);
+
+  // Setup wake up GPIO and enter deep sleep
+  // Should be called inside main loop() to handle the currentLockMode
+  void startDeepSleep(HalGPIO& gpio) const;
+
+  // Get battery percentage (range 0-100)
+  int getBatteryPercentage() const;
+
+  // RAII helper class to manage power saving locks
+  // Usage: create an instance of Lock in a scope to disable power saving, for example when running a task that needs
+  // full performance. When the Lock instance is destroyed (goes out of scope), power saving will be re-enabled.
+  class Lock {
+    friend class HalPowerManager;
+    bool valid = false;
+
+   public:
+    explicit Lock();
+    ~Lock();
+
+    // Non-copyable and non-movable
+    Lock(const Lock&) = delete;
+    Lock& operator=(const Lock&) = delete;
+    Lock(Lock&&) = delete;
+    Lock& operator=(Lock&&) = delete;
+  };
+};

src/activities/Activity.cpp

@@ -1,5 +1,7 @@
 #include "Activity.h"
 
+#include <HalPowerManager.h>
+
 void Activity::renderTaskTrampoline(void* param) {
   auto* self = static_cast<Activity*>(param);
   self->renderTaskLoop();
@@ -9,6 +11,7 @@ void Activity::renderTaskLoop() {
   while (true) {
     ulTaskNotifyTake(pdTRUE, portMAX_DELAY);
     {
+      HalPowerManager::Lock powerLock;  // Ensure we don't go into low-power mode while rendering
       RenderLock lock(*this);
       render(std::move(lock));
     }

src/activities/ActivityWithSubactivity.cpp

@@ -1,9 +1,12 @@
 #include "ActivityWithSubactivity.h"
 
+#include <HalPowerManager.h>
+
 void ActivityWithSubactivity::renderTaskLoop() {
   while (true) {
     ulTaskNotifyTake(pdTRUE, portMAX_DELAY);
     {
+      HalPowerManager::Lock powerLock;  // Ensure we don't go into low-power mode while rendering
       RenderLock lock(*this);
       if (!subActivity) {
         render(std::move(lock));

src/activities/browser/OpdsBookBrowserActivity.cpp

@@ -189,7 +189,7 @@ void OpdsBookBrowserActivity::render(Activity::RenderLock&&) {
   if (!entries.empty() && entries[selectorIndex].type == OpdsEntryType::BOOK) {
     confirmLabel = tr(STR_DOWNLOAD);
   }
-  const auto labels = mappedInput.mapLabels(tr(STR_BACK), confirmLabel, "", "");
+  const auto labels = mappedInput.mapLabels(tr(STR_BACK), confirmLabel, tr(STR_DIR_UP), tr(STR_DIR_DOWN));
   GUI.drawButtonHints(renderer, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
 
   if (entries.empty()) {

src/activities/home/MyLibraryActivity.cpp

@@ -196,8 +196,8 @@ void MyLibraryActivity::render(Activity::RenderLock&&) {
   const auto pageHeight = renderer.getScreenHeight();
   auto metrics = UITheme::getInstance().getMetrics();
 
-  auto folderName = basepath == "/" ? tr(STR_SD_CARD) : basepath.substr(basepath.rfind('/') + 1).c_str();
+  std::string folderName = (basepath == "/") ? tr(STR_SD_CARD) : basepath.substr(basepath.rfind('/') + 1);
-  GUI.drawHeader(renderer, Rect{0, metrics.topPadding, pageWidth, metrics.headerHeight}, folderName);
+  GUI.drawHeader(renderer, Rect{0, metrics.topPadding, pageWidth, metrics.headerHeight}, folderName.c_str());
 
   const int contentTop = metrics.topPadding + metrics.headerHeight + metrics.verticalSpacing;
   const int contentHeight = pageHeight - contentTop - metrics.buttonHintsHeight - metrics.verticalSpacing;

src/activities/network/NetworkModeSelectionActivity.cpp

@@ -92,7 +92,7 @@ void NetworkModeSelectionActivity::render(Activity::RenderLock&&) {
   }
 
   // Draw help text at bottom
-  const auto labels = mappedInput.mapLabels(tr(STR_BACK), tr(STR_SELECT), "", "");
+  const auto labels = mappedInput.mapLabels(tr(STR_BACK), tr(STR_SELECT), tr(STR_DIR_UP), tr(STR_DIR_DOWN));
   GUI.drawButtonHints(renderer, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
 
   renderer.displayBuffer();

src/activities/reader/KOReaderSyncActivity.cpp

@@ -310,8 +310,8 @@ void KOReaderSyncActivity::render(Activity::RenderLock&&) {
     }
     renderer.drawText(UI_10_FONT_ID, 20, optionY + optionHeight, tr(STR_UPLOAD_LOCAL), selectedOption != 1);
 
-    // Bottom button hints: show Back and Select
+    // Bottom button hints
-    const auto labels = mappedInput.mapLabels(tr(STR_BACK), tr(STR_SELECT), "", "");
+    const auto labels = mappedInput.mapLabels(tr(STR_BACK), tr(STR_SELECT), tr(STR_DIR_UP), tr(STR_DIR_DOWN));
     GUI.drawButtonHints(renderer, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
     renderer.displayBuffer();
     return;

src/activities/settings/CalibreSettingsActivity.cpp

@@ -149,7 +149,7 @@ void CalibreSettingsActivity::render(Activity::RenderLock&&) {
   }
 
   // Draw button hints
-  const auto labels = mappedInput.mapLabels(tr(STR_BACK), tr(STR_SELECT), "", "");
+  const auto labels = mappedInput.mapLabels(tr(STR_BACK), tr(STR_SELECT), tr(STR_DIR_UP), tr(STR_DIR_DOWN));
   GUI.drawButtonHints(renderer, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
 
   renderer.displayBuffer();

src/activities/settings/ClearCacheActivity.h

@@ -13,6 +13,7 @@ class ClearCacheActivity final : public ActivityWithSubactivity {
   void onEnter() override;
   void onExit() override;
   void loop() override;
+  bool skipLoopDelay() override { return true; }  // Prevent power-saving mode
   void render(Activity::RenderLock&&) override;
 
  private:

src/activities/settings/KOReaderSettingsActivity.cpp

@@ -173,7 +173,7 @@ void KOReaderSettingsActivity::render(Activity::RenderLock&&) {
   }
 
   // Draw button hints
-  const auto labels = mappedInput.mapLabels(tr(STR_BACK), tr(STR_SELECT), "", "");
+  const auto labels = mappedInput.mapLabels(tr(STR_BACK), tr(STR_SELECT), tr(STR_DIR_UP), tr(STR_DIR_DOWN));
   GUI.drawButtonHints(renderer, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
 
   renderer.displayBuffer();

src/activities/settings/LanguageSelectActivity.cpp

@@ -87,7 +87,7 @@ void LanguageSelectActivity::render(Activity::RenderLock&&) {
   }
 
   // Button hints
-  const auto labels = mappedInput.mapLabels(tr(STR_BACK), tr(STR_SELECT), "", "");
+  const auto labels = mappedInput.mapLabels(tr(STR_BACK), tr(STR_SELECT), tr(STR_DIR_UP), tr(STR_DIR_DOWN));
   GUI.drawButtonHints(renderer, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
 
   renderer.displayBuffer();

src/activities/settings/OtaUpdateActivity.h

@@ -34,4 +34,5 @@ class OtaUpdateActivity : public ActivityWithSubactivity {
   void loop() override;
   void render(Activity::RenderLock&&) override;
   bool preventAutoSleep() override { return state == CHECKING_FOR_UPDATE || state == UPDATE_IN_PROGRESS; }
+  bool skipLoopDelay() override { return true; }  // Prevent power-saving mode
 };

src/main.cpp

@@ -3,6 +3,7 @@
 #include <GfxRenderer.h>
 #include <HalDisplay.h>
 #include <HalGPIO.h>
+#include <HalPowerManager.h>
 #include <HalStorage.h>
 #include <I18n.h>
 #include <Logging.h>
@@ -183,7 +184,7 @@ void verifyPowerButtonDuration() {
   if (abort) {
     // Button released too early. Returning to sleep.
     // IMPORTANT: Re-arm the wakeup trigger before sleeping again
-    gpio.startDeepSleep();
+    powerManager.startDeepSleep(gpio);
   }
 }
 
@@ -206,7 +207,7 @@ void enterDeepSleep() {
   LOG_DBG("MAIN", "Power button press calibration value: %lu ms", t2 - t1);
   LOG_DBG("MAIN", "Entering deep sleep");
 
-  gpio.startDeepSleep();
+  powerManager.startDeepSleep(gpio);
 }
 
 void onGoHome();
@@ -283,6 +284,7 @@ void setup() {
   t1 = millis();
 
   gpio.begin();
+  powerManager.begin();
 
   // Only start serial if USB connected
   if (gpio.isUsbConnected()) {
@@ -319,7 +321,7 @@ void setup() {
     case HalGPIO::WakeupReason::AfterUSBPower:
       // If USB power caused a cold boot, go back to sleep
       LOG_DBG("MAIN", "Wakeup reason: After USB Power");
-      gpio.startDeepSleep();
+      powerManager.startDeepSleep(gpio);
       break;
     case HalGPIO::WakeupReason::AfterFlash:
       // After flashing, just proceed to boot
@@ -392,6 +394,7 @@ void loop() {
   static unsigned long lastActivityTime = millis();
   if (gpio.wasAnyPressed() || gpio.wasAnyReleased() || (currentActivity && currentActivity->preventAutoSleep())) {
     lastActivityTime = millis();         // Reset inactivity timer
+    powerManager.setPowerSaving(false);  // Restore normal CPU frequency on user activity
   }
 
   const unsigned long sleepTimeoutMs = SETTINGS.getSleepTimeoutMs();
@@ -426,11 +429,12 @@ void loop() {
   // When an activity requests skip loop delay (e.g., webserver running), use yield() for faster response
   // Otherwise, use longer delay to save power
   if (currentActivity && currentActivity->skipLoopDelay()) {
+    powerManager.setPowerSaving(false);  // Make sure we're at full performance when skipLoopDelay is requested
     yield();                             // Give FreeRTOS a chance to run tasks, but return immediately
   } else {
-    static constexpr unsigned long IDLE_POWER_SAVING_MS = 3000;  // 3 seconds
+    if (millis() - lastActivityTime >= HalPowerManager::IDLE_POWER_SAVING_MS) {
-    if (millis() - lastActivityTime >= IDLE_POWER_SAVING_MS) {
       // If we've been inactive for a while, increase the delay to save power
+      powerManager.setPowerSaving(true);  // Lower CPU frequency after extended inactivity
       delay(50);
     } else {
       // Short delay to prevent tight loop while still being responsive