[Light Switch] Refactor + cleaner behavior (#43159)

<!-- Enter a brief description/summary of your PR here. What does it
fix/what does it change/how was it tested (even manually, if necessary)?
-->
## Summary of the Pull Request
This PR also includes a refactor to the light switch service. The
refactor will help me make cleaner updates in the future and makes the
"state" easier to track through the service.

## Validation
Completed the following steps as testing for normal behavior and edge
cases:

1. Start up
- Check defaults (delete settings.json files)
- Ensure PowerToys properly starts/does not start the module
- Ensure turning the module on and off starts/terminates the service
- Ensure the settings in the settings file are reflected in the front
end
2. Manual Override Activation
- Ensure that pressing the shortcut key triggers an update
- Ensure that pressing the shortcut key triggers a block in the schedule
(Should see logs Skipping schedule due to manual override)
- Ensure that changing windows settings triggers a manual override (at
the next minute)
- Ensure in both scenarios that the schedule is ignored until a boundary
is met
- Ensure that the schedule resumes following the boundary clearance.
4. New Day Detection / Sun Time Recalculation
- Keep service running past midnight (or simulate date change)
- Verify the last updated day is updated
- Verify new sun times are accurate and set in settings.
5. Coordinates / Mode Change
- Ensure that updates occur when the coordinates or mode changes. These
updates should reflect the new settings.
6. Schedule Mode OFF
- Turn the schedule off, check logs for notice
- Ensure the shortcut still works
- Ensure the schedule resumes as expected once turned back on.
8. Sleep / Hibernate Resume
- Set your schedule to change themes in the next 2 minutes.
- Send your machine to hibernate shutdown /h 
- Wake your machine after your theme should have changed and ensure
Light Switch catches itself up
- Repeat steps above but with a manual override triggered prior to the
theme change.Ensure manual override is flushed and schedule resumes.
9. Stop and Restart behavior
- Stop and restart the module. Ensure it behaves as expected. No reset
settings, etc.

src/modules/LightSwitch/LightSwitchService/LightSwitchService.cpp

@@ -11,7 +11,6 @@
 #include <logger/logger_settings.h>
 #include <logger/logger.h>
 #include <utils/logger_helper.h>
-#include <LightSwitchServiceObserver.h>
 
 SERVICE_STATUS g_ServiceStatus = {};
 SERVICE_STATUS_HANDLE g_StatusHandle = nullptr;
@@ -20,6 +19,7 @@ extern int g_lastUpdatedDay = -1;
 static ScheduleMode prevMode = ScheduleMode::Off;
 static std::wstring prevLat, prevLon;
 static int prevMinutes = -1;
+static bool lastOverrideStatus = false;
 
 VOID WINAPI ServiceMain(DWORD argc, LPTSTR* argv);
 VOID WINAPI ServiceCtrlHandler(DWORD dwCtrl);
@@ -164,48 +164,8 @@ DWORD WINAPI ServiceWorkerThread(LPVOID lpParam)
 
     LightSwitchSettings::instance().InitFileWatcher();
 
-    LightSwitchServiceObserver observer({ SettingId::LightTime,
-                                          SettingId::DarkTime,
-                                          SettingId::ScheduleMode,
-                                          SettingId::Sunrise_Offset,
-                                          SettingId::Sunset_Offset });
-
     HANDLE hManualOverride = OpenEventW(SYNCHRONIZE | EVENT_MODIFY_STATE, FALSE, L"POWERTOYS_LIGHTSWITCH_MANUAL_OVERRIDE");
 
-    auto applyTheme = [](int nowMinutes, int lightMinutes, int darkMinutes, const auto& settings) {
-        bool isLightActive = (lightMinutes < darkMinutes) ? (nowMinutes >= lightMinutes && nowMinutes < darkMinutes) : (nowMinutes >= lightMinutes || nowMinutes < darkMinutes);
-
-        bool isSystemCurrentlyLight = GetCurrentSystemTheme();
-        bool isAppsCurrentlyLight = GetCurrentAppsTheme();
-
-        if (isLightActive)
-        {
-            if (settings.changeSystem && !isSystemCurrentlyLight)
-            {
-                SetSystemTheme(true);
-                Logger::info(L"[LightSwitchService] Changing system theme to light mode.");
-            }
-            if (settings.changeApps && !isAppsCurrentlyLight)
-            {
-                SetAppsTheme(true);
-                Logger::info(L"[LightSwitchService] Changing apps theme to light mode.");
-            }
-        }
-        else
-        {
-            if (settings.changeSystem && isSystemCurrentlyLight)
-            {
-                SetSystemTheme(false);
-                Logger::info(L"[LightSwitchService] Changing system theme to dark mode.");
-            }
-            if (settings.changeApps && isAppsCurrentlyLight)
-            {
-                SetAppsTheme(false);
-                Logger::info(L"[LightSwitchService] Changing apps theme to dark mode.");
-            }
-        }
-    };
-
     LightSwitchSettings::instance().LoadSettings();
     auto& settings = LightSwitchSettings::instance().settings();
 
@@ -213,22 +173,22 @@ DWORD WINAPI ServiceWorkerThread(LPVOID lpParam)
     GetLocalTime(&st);
     int nowMinutes = st.wHour * 60 + st.wMinute;
 
+    // Handle initial theme application if necessary
     if (settings.scheduleMode != ScheduleMode::Off)
     {
-        applyTheme(nowMinutes,
+        Logger::info(L"[LightSwitchService] Schedule mode is set to {}. Applying theme if necessary.", settings.scheduleMode);
-                   settings.lightTime + settings.sunrise_offset,
+        LightSwitchSettings::instance().ApplyThemeIfNecessary();
-                   settings.darkTime + settings.sunset_offset,
-                   settings);
-        Logger::trace(L"[LightSwitchService] Initialized g_lastUpdatedDay = {}", g_lastUpdatedDay);
     }
     else
     {
-        Logger::info(L"[LightSwitchService] Schedule mode is OFF - ticker suspended, waiting for manual action or mode change.");
+        Logger::info(L"[LightSwitchService] Schedule mode is set to Off.");
     }
 
     g_lastUpdatedDay = st.wDay;
+    Logger::info(L"[LightSwitchService] Initializing g_lastUpdatedDay to {}.", g_lastUpdatedDay);
     ULONGLONG lastSettingsReload = 0;
 
+    // ticker loop
     for (;;)
     {
         HANDLE waits[2] = { g_ServiceStopEvent, hParent };
@@ -237,13 +197,10 @@ DWORD WINAPI ServiceWorkerThread(LPVOID lpParam)
 
         const auto& settings = LightSwitchSettings::instance().settings();
 
-        bool scheduleJustEnabled = (prevMode == ScheduleMode::Off && settings.scheduleMode != ScheduleMode::Off);
+        // If the mode is set to Off, suspend the scheduler and avoid extra work
-        prevMode = settings.scheduleMode;
-
-        // ─── Handle "Schedule Off" Mode ─────────────────────────────────────────────
         if (settings.scheduleMode == ScheduleMode::Off)
         {
-            Logger::info(L"[LightSwitchService] Schedule mode OFF - suspending scheduler but keeping service alive.");
+            Logger::info(L"[LightSwitchService] Schedule mode is OFF - suspending scheduler but keeping service alive.");
 
             if (!hManualOverride)
                 hManualOverride = OpenEventW(SYNCHRONIZE | EVENT_MODIFY_STATE, FALSE, L"POWERTOYS_LIGHTSWITCH_MANUAL_OVERRIDE");
@@ -283,7 +240,6 @@ DWORD WINAPI ServiceWorkerThread(LPVOID lpParam)
                 {
                     Logger::trace(L"[LightSwitchService] Settings change event triggered, reloading settings...");
                     ResetEvent(LightSwitchSettings::instance().GetSettingsChangedEvent());
-                    LightSwitchSettings::instance().LoadSettings();
                     const auto& newSettings = LightSwitchSettings::instance().settings();
                     lastSettingsReload = GetTickCount64();
 
@@ -298,73 +254,150 @@ DWORD WINAPI ServiceWorkerThread(LPVOID lpParam)
             continue;
         }
 
-        // ─── Normal Schedule Loop ───────────────────────────────────────────────────
+        bool scheduleJustEnabled = (prevMode == ScheduleMode::Off && settings.scheduleMode != ScheduleMode::Off);
+        prevMode = settings.scheduleMode;
+
         ULONGLONG nowTick = GetTickCount64();
-        bool recentSettingsReload = (nowTick - lastSettingsReload < 5000);
+        bool recentSettingsReload = (nowTick - lastSettingsReload < 2000);
 
-        if (g_lastUpdatedDay != -1)
+        Logger::debug(L"[LightSwitchService] Current g_lastUpdatedDay value = {}.", g_lastUpdatedDay);
+
+        // Manual Override Detection Logic
+        bool manualOverrideActive = (hManualOverride && WaitForSingleObject(hManualOverride, 0) == WAIT_OBJECT_0);
+
+        if (manualOverrideActive != lastOverrideStatus)
         {
-            bool manualOverrideActive = (hManualOverride && WaitForSingleObject(hManualOverride, 0) == WAIT_OBJECT_0);
+            Logger::debug(L"[LightSwitchService] Manual override active = {}", manualOverrideActive);
+            lastOverrideStatus = manualOverrideActive;
+        }
 
-            if (settings.scheduleMode != ScheduleMode::Off && !recentSettingsReload && !scheduleJustEnabled)
+        if (settings.scheduleMode != ScheduleMode::Off && !recentSettingsReload && !scheduleJustEnabled && !manualOverrideActive)
+        {
+            bool currentSystemTheme = GetCurrentSystemTheme();
+            bool currentAppsTheme = GetCurrentAppsTheme();
+
+            SYSTEMTIME st;
+            GetLocalTime(&st);
+            int nowMinutes = st.wHour * 60 + st.wMinute;
+
+            int lightBoundary = 0;
+            int darkBoundary = 0;
+
+            if (settings.scheduleMode == ScheduleMode::SunsetToSunrise)
             {
-                Logger::debug(L"[LightSwitchService] Checking if manual override is active...");
+                lightBoundary = (settings.lightTime + settings.sunrise_offset) % 1440;
-                bool manualOverrideActive = (hManualOverride && WaitForSingleObject(hManualOverride, 0) == WAIT_OBJECT_0);
+                darkBoundary = (settings.darkTime + settings.sunset_offset) % 1440;
-                Logger::debug(L"[LightSwitchService] Manual override active = {}", manualOverrideActive);
-
-                if (!manualOverrideActive)
-                {
-                    bool currentSystemTheme = GetCurrentSystemTheme();
-                    bool currentAppsTheme = GetCurrentAppsTheme();
-
-                    SYSTEMTIME st;
-                    GetLocalTime(&st);
-                    int nowMinutes = st.wHour * 60 + st.wMinute;
-
-                    bool shouldBeLight = (settings.lightTime < settings.darkTime) ? (nowMinutes >= settings.lightTime && nowMinutes < settings.darkTime) : (nowMinutes >= settings.lightTime || nowMinutes < settings.darkTime);
-
-                    Logger::debug(L"[LightSwitchService] shouldBeLight = {}", shouldBeLight);
-
-                    if ((settings.changeSystem && (currentSystemTheme != shouldBeLight)) ||
-                        (settings.changeApps && (currentAppsTheme != shouldBeLight)))
-                    {
-                        Logger::debug(L"[LightSwitchService] External theme change detected - enabling manual override");
-
-                        if (!hManualOverride)
-                        {
-                            hManualOverride = OpenEventW(SYNCHRONIZE | EVENT_MODIFY_STATE, FALSE, L"POWERTOYS_LIGHTSWITCH_MANUAL_OVERRIDE");
-                            if (!hManualOverride)
-                                hManualOverride = CreateEventW(nullptr, TRUE, FALSE, L"POWERTOYS_LIGHTSWITCH_MANUAL_OVERRIDE");
-                        }
-
-                        if (hManualOverride)
-                        {
-                            SetEvent(hManualOverride);
-                            Logger::info(L"[LightSwitchService] Detected manual theme change outside of LightSwitch. Triggering manual override.");
-                            skipRest = true;
-                        }
-                    }
-                }
             }
             else
             {
-                Logger::debug(L"[LightSwitchService] Skipping external-change detection (schedule off, recent reload, or just enabled).");
+                lightBoundary = settings.lightTime;
+                darkBoundary = settings.darkTime;
+            }
+
+            bool shouldBeLight = (lightBoundary < darkBoundary) ? (nowMinutes >= lightBoundary && nowMinutes < darkBoundary) : (nowMinutes >= lightBoundary || nowMinutes < darkBoundary);
+
+            Logger::debug(L"[LightSwitchService] shouldBeLight = {}", shouldBeLight);
+
+            bool systemMismatch = settings.changeSystem && (currentSystemTheme != shouldBeLight);
+            bool appsMismatch = settings.changeApps && (currentAppsTheme != shouldBeLight);
+
+            if (systemMismatch || appsMismatch)
+            {
+              // Make sure this is not because we crossed a boundary
+              bool crossedBoundary = false;
+              if (prevMinutes != -1)
+              {
+                  if (nowMinutes < prevMinutes)
+                  {
+                      // wrapped around midnight
+                      crossedBoundary = (prevMinutes <= lightBoundary || nowMinutes >= lightBoundary) ||
+                                        (prevMinutes <= darkBoundary || nowMinutes >= darkBoundary);
+                  }
+                  else
+                  {
+                      crossedBoundary = (prevMinutes < lightBoundary && nowMinutes >= lightBoundary) ||
+                                        (prevMinutes < darkBoundary && nowMinutes >= darkBoundary);
+                  }
+              }
+
+              if (crossedBoundary)
+              {
+                  Logger::info(L"[LightSwitchService] Missed boundary detected. Applying theme instead of triggering manual override.");
+                  LightSwitchSettings::instance().ApplyThemeIfNecessary();
+              }
+              else
+              {
+                  Logger::info(L"[LightSwitchService] External {} theme change detected, enabling manual override.",
+                               systemMismatch && appsMismatch ? L"system/app" :
+                               systemMismatch                 ? L"system" :
+                                                                L"app");
+                  SetEvent(hManualOverride);
+                  skipRest = true;
+              }
+            }
+        }
+        else
+        {
+            Logger::debug(L"[LightSwitchService] Skipping external-change detection (schedule off, recent reload, or just enabled).");
+        }
+        
+        if (hManualOverride)
+            manualOverrideActive = (WaitForSingleObject(hManualOverride, 0) == WAIT_OBJECT_0);
+
+        if (manualOverrideActive)
+        {
+            int lightBoundary = (settings.lightTime + settings.sunrise_offset) % 1440;
+            int darkBoundary = (settings.darkTime + settings.sunset_offset) % 1440;
+
+            SYSTEMTIME st;
+            GetLocalTime(&st);
+            nowMinutes = st.wHour * 60 + st.wMinute;
+
+            bool crossedLight = false;
+            bool crossedDark = false;
+
+            if (prevMinutes != -1)
+            {
+                // this means we are in a new day cycle
+                if (nowMinutes < prevMinutes)
+                {
+                    crossedLight = (prevMinutes <= lightBoundary || nowMinutes >= lightBoundary);
+                    crossedDark = (prevMinutes <= darkBoundary || nowMinutes >= darkBoundary);
+                }
+                else
+                {
+                    crossedLight = (prevMinutes < lightBoundary && nowMinutes >= lightBoundary);
+                    crossedDark = (prevMinutes < darkBoundary && nowMinutes >= darkBoundary);
+                }
+            }
+
+            if (crossedLight || crossedDark)
+            {
+                ResetEvent(hManualOverride);
+                Logger::info(L"[LightSwitchService] Manual override cleared after crossing schedule boundary.");
+            }
+            else
+            {
+                Logger::debug(L"[LightSwitchService] Skipping schedule due to manual override");
+                skipRest = true;
             }
         }
 
-        // ─── Apply Schedule Logic ───────────────────────────────────────────────────
+        // Apply theme if nothing has made us skip
         if (!skipRest)
         {
+            // Next two conditionals check for any updates necessary to the sun times.
             bool modeChangedToSunset = (prevMode != settings.scheduleMode &&
                                         settings.scheduleMode == ScheduleMode::SunsetToSunrise);
             bool coordsChanged = (prevLat != settings.latitude || prevLon != settings.longitude);
 
             if ((modeChangedToSunset || coordsChanged) && settings.scheduleMode == ScheduleMode::SunsetToSunrise)
             {
-                Logger::info(L"[LightSwitchService] Mode or coordinates changed, recalculating sun times.");
-                update_sun_times(settings);
                 SYSTEMTIME st;
                 GetLocalTime(&st);
+
+                Logger::info(L"[LightSwitchService] Mode or coordinates changed, recalculating sun times.");
+                update_sun_times(settings);
                 g_lastUpdatedDay = st.wDay;
                 prevMode = settings.scheduleMode;
                 prevLat = settings.latitude;
@@ -383,70 +416,23 @@ DWORD WINAPI ServiceWorkerThread(LPVOID lpParam)
                 Logger::info(L"[LightSwitchService] Recalculated sun times at new day boundary.");
             }
 
+            // settings after any necessary updates.
             LightSwitchSettings::instance().LoadSettings();
             const auto& currentSettings = LightSwitchSettings::instance().settings();
 
             wchar_t msg[160];
             swprintf_s(msg,
-                       L"[LightSwitchService] now=%02d:%02d | light=%02d:%02d | dark=%02d:%02d | mode=%d",
+                       L"[LightSwitchService] now=%02d:%02d | light=%02d:%02d | dark=%02d:%02d | mode=%s",
                        st.wHour,
                        st.wMinute,
                        currentSettings.lightTime / 60,
                        currentSettings.lightTime % 60,
                        currentSettings.darkTime / 60,
                        currentSettings.darkTime % 60,
-                       static_cast<int>(currentSettings.scheduleMode));
+                       ToString(currentSettings.scheduleMode).c_str());
             Logger::info(msg);
 
-            bool manualOverrideActive = false;
+            LightSwitchSettings::instance().ApplyThemeIfNecessary();
-            if (hManualOverride)
-                manualOverrideActive = (WaitForSingleObject(hManualOverride, 0) == WAIT_OBJECT_0);
-
-            if (manualOverrideActive)
-            {
-                int lightBoundary = (currentSettings.lightTime + currentSettings.sunrise_offset) % 1440;
-                int darkBoundary = (currentSettings.darkTime + currentSettings.sunset_offset) % 1440;
-
-                bool crossedLight = false;
-                bool crossedDark = false;
-
-                if (prevMinutes != -1)
-                {
-                    if (nowMinutes < prevMinutes)
-                    {
-                        crossedLight = (prevMinutes <= lightBoundary || nowMinutes >= lightBoundary);
-                        crossedDark = (prevMinutes <= darkBoundary || nowMinutes >= darkBoundary);
-                    }
-                    else
-                    {
-                        crossedLight = (prevMinutes < lightBoundary && nowMinutes >= lightBoundary);
-                        crossedDark = (prevMinutes < darkBoundary && nowMinutes >= darkBoundary);
-                    }
-                }
-
-                Logger::debug(L"[LightSwitchService] prevMinutes={} nowMinutes={} light={} dark={}",
-                              prevMinutes,
-                              nowMinutes,
-                              lightBoundary,
-                              darkBoundary);
-
-                if (crossedLight || crossedDark)
-                {
-                    ResetEvent(hManualOverride);
-                    Logger::info(L"[LightSwitchService] Manual override cleared after crossing schedule boundary.");
-                }
-                else
-                {
-                    Logger::info(L"[LightSwitchService] Skipping schedule due to manual override");
-                    skipRest = true;
-                }
-            }
-
-            if (!skipRest)
-                applyTheme(nowMinutes,
-                           currentSettings.lightTime + currentSettings.sunrise_offset,
-                           currentSettings.darkTime + currentSettings.sunset_offset,
-                           currentSettings);
         }
 
         // ─── Wait For Next Minute Tick Or Stop Event ────────────────────────────────
@@ -480,54 +466,6 @@ cleanup:
     return 0;
 }
 
-void ApplyThemeNow()
-{
-    LightSwitchSettings::instance().LoadSettings();
-    const auto& settings = LightSwitchSettings::instance().settings();
-
-    SYSTEMTIME st;
-    GetLocalTime(&st);
-    int nowMinutes = st.wHour * 60 + st.wMinute;
-
-    bool shouldBeLight = false;
-    if (settings.lightTime < settings.darkTime)
-        shouldBeLight = (nowMinutes >= settings.lightTime && nowMinutes < settings.darkTime);
-    else
-        shouldBeLight = (nowMinutes >= settings.lightTime || nowMinutes < settings.darkTime);
-
-    bool isSystemCurrentlyLight = GetCurrentSystemTheme();
-    bool isAppsCurrentlyLight = GetCurrentAppsTheme();
-
-    Logger::info(L"[LightSwitchService] Applying (if needed) theme immediately due to schedule change.");
-
-    if (shouldBeLight)
-    {
-        if (settings.changeSystem && !isSystemCurrentlyLight)
-        {
-            SetSystemTheme(true);
-            Logger::info(L"[LightSwitchService] Changing system theme to light mode.");
-        }
-        if (settings.changeApps && !isAppsCurrentlyLight)
-        {
-            SetAppsTheme(true);
-            Logger::info(L"[LightSwitchService] Changing apps theme to light mode.");
-        }
-    }
-    else
-    {
-        if (settings.changeSystem && isSystemCurrentlyLight)
-        {
-            SetSystemTheme(false);
-            Logger::info(L"[LightSwitchService] Changing system theme to dark mode.");
-        }
-        if (settings.changeApps && isAppsCurrentlyLight)
-        {
-            SetAppsTheme(false);
-            Logger::info(L"[LightSwitchService] Changing apps theme to dark mode.");
-        }
-    }
-}
-
 int APIENTRY wWinMain(HINSTANCE, HINSTANCE, PWSTR, int)
 {
     if (powertoys_gpo::getConfiguredLightSwitchEnabledValue() == powertoys_gpo::gpo_rule_configured_disabled)

src/modules/LightSwitch/LightSwitchService/LightSwitchService.vcxproj

@@ -74,7 +74,6 @@
   </ItemDefinitionGroup>
   <ItemGroup>
     <ClCompile Include="LightSwitchService.cpp" />
-    <ClCompile Include="LightSwitchServiceObserver.cpp" />
     <ClCompile Include="LightSwitchSettings.cpp" />
     <ClCompile Include="SettingsConstants.cpp" />
     <ClCompile Include="ThemeHelper.cpp" />
@@ -85,7 +84,6 @@
     <ResourceCompile Include="LightSwitchService.rc" />
   </ItemGroup>
   <ItemGroup>
-    <ClInclude Include="LightSwitchServiceObserver.h" />
     <ClInclude Include="LightSwitchSettings.h" />
     <ClInclude Include="SettingsConstants.h" />
     <ClInclude Include="SettingsObserver.h" />

src/modules/LightSwitch/LightSwitchService/LightSwitchService.vcxproj.filters

@@ -33,9 +33,6 @@
     <ClCompile Include="WinHookEventIDs.cpp">
       <Filter>Source Files</Filter>
     </ClCompile>
-    <ClCompile Include="LightSwitchServiceObserver.cpp">
-      <Filter>Source Files</Filter>
-    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="ThemeScheduler.h">
@@ -56,9 +53,6 @@
     <ClInclude Include="WinHookEventIDs.h">
       <Filter>Header Files</Filter>
     </ClInclude>
-    <ClInclude Include="LightSwitchServiceObserver.h">
-      <Filter>Header Files</Filter>
-    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <Natvis Include="$(MSBuildThisFileDirectory)..\..\natvis\wil.natvis" />

src/modules/LightSwitch/LightSwitchService/LightSwitchServiceObserver.cpp

@@ -1,29 +0,0 @@
-#include "LightSwitchServiceObserver.h"
-#include <logger.h>
-#include "LightSwitchSettings.h"
-
-// These are defined elsewhere in your service module (ServiceWorkerThread.cpp)
-extern int g_lastUpdatedDay;
-void ApplyThemeNow();
-
-void LightSwitchServiceObserver::SettingsUpdate(SettingId id)
-{
-    Logger::info(L"[LightSwitchService] Setting changed: {}", static_cast<int>(id));
-    g_lastUpdatedDay = -1;
-    ApplyThemeNow();
-}
-
-bool LightSwitchServiceObserver::WantsToBeNotified(SettingId id) const noexcept
-{
-    switch (id)
-    {
-    case SettingId::LightTime:
-    case SettingId::DarkTime:
-    case SettingId::ScheduleMode:
-    case SettingId::Sunrise_Offset:
-    case SettingId::Sunset_Offset:
-        return true;
-    default:
-        return false;
-    }
-}

src/modules/LightSwitch/LightSwitchService/LightSwitchServiceObserver.h

@@ -1,16 +0,0 @@
-#pragma once
-
-#include "SettingsObserver.h"
-
-// The LightSwitchServiceObserver reacts when LightSwitchSettings changes.
-class LightSwitchServiceObserver : public SettingsObserver
-{
-public:
-    explicit LightSwitchServiceObserver(std::unordered_set<SettingId> observedSettings) :
-        SettingsObserver(std::move(observedSettings))
-    {
-    }
-
-    void SettingsUpdate(SettingId id) override;
-    bool WantsToBeNotified(SettingId id) const noexcept override;
-};

src/modules/LightSwitch/LightSwitchService/LightSwitchSettings.cpp

@@ -2,7 +2,7 @@
 #include <common/utils/json.h>
 #include <common/SettingsAPI/settings_helpers.h>
 #include "SettingsObserver.h"
-
+#include "ThemeHelper.h"
 #include <filesystem>
 #include <fstream>
 #include <WinHookEventIDs.h>
@@ -38,13 +38,80 @@ void LightSwitchSettings::InitFileWatcher()
         m_settingsFileWatcher = std::make_unique<FileWatcher>(
             GetSettingsFileName(),
             [this]() {
-                Logger::info(L"[LightSwitchSettings] Settings file changed, signaling event.");
+                using namespace std::chrono;
-                LoadSettings();
+
-                SetEvent(m_settingsChangedEvent);
+                {
+                    std::lock_guard<std::mutex> lock(m_debounceMutex);
+                    m_lastChangeTime = steady_clock::now();
+                    if (m_debouncePending)
+                        return;
+                    m_debouncePending = true;
+                }
+
+                m_debounceThread = std::jthread([this](std::stop_token stop) {
+                    using namespace std::chrono;
+                    while (!stop.stop_requested())
+                    {
+                        std::this_thread::sleep_for(seconds(3));
+
+                        auto elapsed = steady_clock::now() - m_lastChangeTime;
+                        if (elapsed >= seconds(1))
+                            break;
+                    }
+
+                    {
+                        std::lock_guard<std::mutex> lock(m_debounceMutex);
+                        m_debouncePending = false;
+                    }
+
+                    Logger::info(L"[LightSwitchSettings] Settings file stabilized, reloading.");
+
+                    try
+                    {
+                        LoadSettings();
+                        ApplyThemeIfNecessary();
+                        SetEvent(m_settingsChangedEvent);
+                    }
+                    catch (const std::exception& e)
+                    {
+                        std::wstring wmsg;
+                        wmsg.assign(e.what(), e.what() + strlen(e.what()));
+                        Logger::error(L"[LightSwitchSettings] Exception during debounced reload: {}", wmsg);
+                    }
+                });
             });
     }
 }
 
+LightSwitchSettings::~LightSwitchSettings()
+{
+    Logger::info(L"[LightSwitchSettings] Cleaning up settings resources...");
+
+    // Stop and join the debounce thread (std::jthread auto-joins, but we can signal stop too)
+    if (m_debounceThread.joinable())
+    {
+        m_debounceThread.request_stop();
+    }
+
+    // Release the file watcher so it closes file handles and background threads
+    if (m_settingsFileWatcher)
+    {
+        m_settingsFileWatcher.reset();
+        Logger::info(L"[LightSwitchSettings] File watcher stopped.");
+    }
+
+    // Close the Windows event handle
+    if (m_settingsChangedEvent)
+    {
+        CloseHandle(m_settingsChangedEvent);
+        m_settingsChangedEvent = nullptr;
+        Logger::info(L"[LightSwitchSettings] Settings changed event closed.");
+    }
+
+    Logger::info(L"[LightSwitchSettings] Cleanup complete.");
+}
+
+
 void LightSwitchSettings::AddObserver(SettingsObserver& observer)
 {
     m_observers.insert(&observer);
@@ -73,6 +140,7 @@ HANDLE LightSwitchSettings::GetSettingsChangedEvent() const
 
 void LightSwitchSettings::LoadSettings()
 {
+    std::lock_guard<std::mutex> guard(m_settingsMutex);
     try
     {
         PowerToysSettings::PowerToyValues values =
@@ -181,4 +249,49 @@ void LightSwitchSettings::LoadSettings()
     {
         // Keeps defaults if load fails
     }
+}
+
+void LightSwitchSettings::ApplyThemeIfNecessary()
+{
+    std::lock_guard<std::mutex> guard(m_settingsMutex);
+
+    SYSTEMTIME st;
+    GetLocalTime(&st);
+    int nowMinutes = st.wHour * 60 + st.wMinute;
+
+    bool shouldBeLight = false;
+    if (m_settings.lightTime < m_settings.darkTime)
+        shouldBeLight = (nowMinutes >= m_settings.lightTime && nowMinutes < m_settings.darkTime);
+    else
+        shouldBeLight = (nowMinutes >= m_settings.lightTime || nowMinutes < m_settings.darkTime);
+
+    bool isSystemCurrentlyLight = GetCurrentSystemTheme();
+    bool isAppsCurrentlyLight = GetCurrentAppsTheme();
+
+    if (shouldBeLight)
+    {
+        if (m_settings.changeSystem && !isSystemCurrentlyLight)
+        {
+            SetSystemTheme(true);
+            Logger::info(L"[LightSwitchService] Changing system theme to light mode.");
+        }
+        if (m_settings.changeApps && !isAppsCurrentlyLight)
+        {
+            SetAppsTheme(true);
+            Logger::info(L"[LightSwitchService] Changing apps theme to light mode.");
+        }
+    }
+    else
+    {
+        if (m_settings.changeSystem && isSystemCurrentlyLight)
+        {
+            SetSystemTheme(false);
+            Logger::info(L"[LightSwitchService] Changing system theme to dark mode.");
+        }
+        if (m_settings.changeApps && isAppsCurrentlyLight)
+        {
+            SetAppsTheme(false);
+            Logger::info(L"[LightSwitchService] Changing apps theme to dark mode.");
+        }
+    }
 }

src/modules/LightSwitch/LightSwitchService/LightSwitchSettings.h

@@ -5,7 +5,10 @@
 #include <vector>
 #include <memory>
 #include <windows.h>
-
+#include <mutex>
+#include <atomic>
+#include <thread>
+#include <chrono>
 #include <common/SettingsAPI/FileWatcher.h>
 #include <common/SettingsAPI/settings_objects.h>
 #include <SettingsConstants.h>
@@ -78,12 +81,13 @@ public:
     void RemoveObserver(SettingsObserver& observer);
 
     void LoadSettings();
+    void ApplyThemeIfNecessary();
 
     HANDLE GetSettingsChangedEvent() const;
 
 private:
     LightSwitchSettings();
-    ~LightSwitchSettings() = default;
+    ~LightSwitchSettings();
 
     LightSwitchConfig m_settings;
     std::unique_ptr<FileWatcher> m_settingsFileWatcher;
@@ -92,4 +96,11 @@ private:
     void NotifyObservers(SettingId id) const;
 
     HANDLE m_settingsChangedEvent = nullptr;
+    mutable std::mutex m_settingsMutex;
+
+    // Debounce state
+    std::atomic_bool m_debouncePending{ false };
+    std::mutex m_debounceMutex;
+    std::chrono::steady_clock::time_point m_lastChangeTime{};
+    std::jthread m_debounceThread;
 };