From 335dcbaae83c8ffb136958a39deceadca35154aa Mon Sep 17 00:00:00 2001
From: Jaylyn Barbee <51131738+Jaylyn-Barbee@users.noreply.github.com>
Date: Mon, 5 Jan 2026 20:54:37 -0500
Subject: [PATCH] [Light Switch] Adding telemetry events (#44241)

Adding events to track the following:
<table style="width:100%">
  <tr>
    <th>Event Name</th>
    <th>Description</th>
<th>Data collected</th>
  </tr>
  <tr>
    <td>Microsoft.PowerToys.LightSwitch_EnableLightSwitch</td>
    <td>Triggered when Light Switch is enabled or disabled.</td>
<td>Whether the module is enabled or disabled (bool)</td>
  </tr>
  <tr>
    <td>Microsoft.PowerToys.LightSwitch_ShortcutInvoked</td>
    <td>Occurs when the shortcut for Light Switch is invoked.</td>
<td></td>
  </tr>
  <tr>
    <td>Microsoft.PowerToys.LightSwitch_ScheduleModeToggled</td>
<td>Occurs when a new schedule mode is selected for Light Switch.</td>
<td>The new mode selected (string)</td>
  </tr>
  <tr>
    <td>Microsoft.PowerToys.LightSwitch_ThemeTargetChanged</td>
<td>Occurs when the options for targeting the system or apps is
updated.</td>
<td>The new options selected (two bools)</td>
  </tr>
</table>

The above events that are related to Light Switch settings are tracked
in the "LoadSettings" function inside the service but only if the value
has changed. The Enabled event as well as the Shortcut event are tracked
in the module interface.
---
 DATA_AND_PRIVACY.md                           | 24 +++++++++++
 .../LightSwitchModuleInterface/dllmain.cpp    |  6 ++-
 .../LightSwitchModuleInterface/trace.cpp      | 15 +++++--
 .../LightSwitchModuleInterface/trace.h        |  3 +-
 .../LightSwitchService/LightSwitchService.cpp |  7 ++-
 .../LightSwitchService.vcxproj                |  2 +
 .../LightSwitchService.vcxproj.filters        |  6 +++
 .../LightSwitchSettings.cpp                   | 12 ++++++
 .../LightSwitch/LightSwitchService/trace.cpp  | 43 +++++++++++++++++++
 .../LightSwitch/LightSwitchService/trace.h    | 17 ++++++++
 10 files changed, 129 insertions(+), 6 deletions(-)
 create mode 100644 src/modules/LightSwitch/LightSwitchService/trace.cpp
 create mode 100644 src/modules/LightSwitch/LightSwitchService/trace.h

diff --git a/DATA_AND_PRIVACY.md b/DATA_AND_PRIVACY.md
index 66a0daa1d8..07089e44c3 100644
--- a/DATA_AND_PRIVACY.md
+++ b/DATA_AND_PRIVACY.md
@@ -694,6 +694,30 @@ _If you want to find diagnostic data events in the source code, these two links
   </tr>
 </table>
 
+### Light Switch
+<table style="width:100%">
+  <tr>
+    <th>Event Name</th>
+    <th>Description</th>
+  </tr>
+  <tr>
+    <td>Microsoft.PowerToys.LightSwitch_EnableLightSwitch</td>
+    <td>Triggered when Light Switch is enabled or disabled.</td>
+  </tr>
+  <tr>
+    <td>Microsoft.PowerToys.LightSwitch_ShortcutInvoked</td>
+    <td>Occurs when the shortcut for Light Switch is invoked.</td>
+  </tr>
+  <tr>
+    <td>Microsoft.PowerToys.LightSwitch_ScheduleModeToggled</td>
+    <td>Occurs when a new schedule mode is selected for Light Switch.</td>
+  </tr>
+  <tr>
+    <td>Microsoft.PowerToys.LightSwitch_ThemeTargetChanged</td>
+    <td>Occurs when the options for targeting the system or apps is updated.</td>
+  </tr>
+</table>
+
 ### Mouse Highlighter
 <table style="width:100%">
   <tr>
diff --git a/src/modules/LightSwitch/LightSwitchModuleInterface/dllmain.cpp b/src/modules/LightSwitch/LightSwitchModuleInterface/dllmain.cpp
index 11cfd412b0..bab4e30797 100644
--- a/src/modules/LightSwitch/LightSwitchModuleInterface/dllmain.cpp
+++ b/src/modules/LightSwitch/LightSwitchModuleInterface/dllmain.cpp
@@ -405,6 +405,7 @@ public:
     {
         m_enabled = true;
         Logger::info(L"Enabling Light Switch module...");
+        Trace::Enable(true);
 
         unsigned long powertoys_pid = GetCurrentProcessId();
         std::wstring args = L"--pid " + std::to_wstring(powertoys_pid);
@@ -482,7 +483,8 @@ public:
             CloseHandle(m_process);
             m_process = nullptr;
         }
-
+        
+        Trace::Enable(false);
         StopToggleListener();
     }
 
@@ -539,6 +541,8 @@ public:
         if (m_enabled)
         {
             Logger::trace(L"Light Switch hotkey pressed");
+            Trace::ShortcutInvoked();
+
             if (!is_process_running())
             {
                 enable();
diff --git a/src/modules/LightSwitch/LightSwitchModuleInterface/trace.cpp b/src/modules/LightSwitch/LightSwitchModuleInterface/trace.cpp
index 57fa1921f7..40fc67e679 100644
--- a/src/modules/LightSwitch/LightSwitchModuleInterface/trace.cpp
+++ b/src/modules/LightSwitch/LightSwitchModuleInterface/trace.cpp
@@ -19,12 +19,21 @@ void Trace::UnregisterProvider()
     TraceLoggingUnregister(g_hProvider);
 }
 
-void Trace::MyEvent()
+void Trace::Enable(bool enabled) noexcept
 {
     TraceLoggingWrite(
         g_hProvider,
-        "PowerToyName_MyEvent",
+        "LightSwitch_EnableLightSwitch",
+        ProjectTelemetryPrivacyDataTag(ProjectTelemetryTag_ProductAndServicePerformance),
+        TraceLoggingKeyword(PROJECT_KEYWORD_MEASURE),
+        TraceLoggingBoolean(enabled, "Enabled"));
+}
+
+void Trace::ShortcutInvoked() noexcept
+{
+    TraceLoggingWrite(
+        g_hProvider,
+        "LightSwitch_ShortcutInvoked",
         ProjectTelemetryPrivacyDataTag(ProjectTelemetryTag_ProductAndServicePerformance),
-        TraceLoggingBoolean(TRUE, "UTCReplace_AppSessionGuid"),
         TraceLoggingKeyword(PROJECT_KEYWORD_MEASURE));
 }
diff --git a/src/modules/LightSwitch/LightSwitchModuleInterface/trace.h b/src/modules/LightSwitch/LightSwitchModuleInterface/trace.h
index 55cdedb2ee..bfa32062b9 100644
--- a/src/modules/LightSwitch/LightSwitchModuleInterface/trace.h
+++ b/src/modules/LightSwitch/LightSwitchModuleInterface/trace.h
@@ -11,5 +11,6 @@ class Trace
 public:
     static void RegisterProvider();
     static void UnregisterProvider();
-    static void MyEvent();
+    static void Enable(bool enabled) noexcept;
+    static void ShortcutInvoked() noexcept;
 };
diff --git a/src/modules/LightSwitch/LightSwitchService/LightSwitchService.cpp b/src/modules/LightSwitch/LightSwitchService/LightSwitchService.cpp
index b6684da54e..8919f4274b 100644
--- a/src/modules/LightSwitch/LightSwitchService/LightSwitchService.cpp
+++ b/src/modules/LightSwitch/LightSwitchService/LightSwitchService.cpp
@@ -14,6 +14,7 @@
 #include "LightSwitchStateManager.h"
 #include <LightSwitchUtils.h>
 #include <NightLightRegistryObserver.h>
+#include <trace.h>
 
 SERVICE_STATUS g_ServiceStatus = {};
 SERVICE_STATUS_HANDLE g_StatusHandle = nullptr;
@@ -357,6 +358,8 @@ DWORD WINAPI ServiceWorkerThread(LPVOID lpParam)
 
 int APIENTRY wWinMain(HINSTANCE, HINSTANCE, PWSTR, int)
 {
+    Trace::LightSwitch::RegisterProvider();
+
     if (powertoys_gpo::getConfiguredLightSwitchEnabledValue() == powertoys_gpo::gpo_rule_configured_disabled)
     {
         wchar_t msg[160];
@@ -364,12 +367,14 @@ int APIENTRY wWinMain(HINSTANCE, HINSTANCE, PWSTR, int)
             msg,
             L"Tried to start with a GPO policy setting the utility to always be disabled. Please contact your systems administrator.");
         Logger::info(msg);
+        Trace::LightSwitch::UnregisterProvider();
         return 0;
     }
-
     int argc = 0;
     LPWSTR* argv = CommandLineToArgvW(GetCommandLineW(), &argc);
     int rc = _tmain(argc, argv); // reuse your existing logic
     LocalFree(argv);
+
+    Trace::LightSwitch::UnregisterProvider();
     return rc;
 }
\ No newline at end of file
diff --git a/src/modules/LightSwitch/LightSwitchService/LightSwitchService.vcxproj b/src/modules/LightSwitch/LightSwitchService/LightSwitchService.vcxproj
index e1c8052de6..b8e51ee489 100644
--- a/src/modules/LightSwitch/LightSwitchService/LightSwitchService.vcxproj
+++ b/src/modules/LightSwitch/LightSwitchService/LightSwitchService.vcxproj
@@ -80,6 +80,7 @@
     <ClCompile Include="SettingsConstants.cpp" />
     <ClCompile Include="ThemeHelper.cpp" />
     <ClCompile Include="ThemeScheduler.cpp" />
+    <ClCompile Include="trace.cpp" />
     <ClCompile Include="WinHookEventIDs.cpp" />
   </ItemGroup>
   <ItemGroup>
@@ -94,6 +95,7 @@
     <ClInclude Include="SettingsObserver.h" />
     <ClInclude Include="ThemeHelper.h" />
     <ClInclude Include="ThemeScheduler.h" />
+    <ClInclude Include="trace.h" />
     <ClInclude Include="WinHookEventIDs.h" />
   </ItemGroup>
   <ItemGroup>
diff --git a/src/modules/LightSwitch/LightSwitchService/LightSwitchService.vcxproj.filters b/src/modules/LightSwitch/LightSwitchService/LightSwitchService.vcxproj.filters
index 55c7bde39b..a704e87073 100644
--- a/src/modules/LightSwitch/LightSwitchService/LightSwitchService.vcxproj.filters
+++ b/src/modules/LightSwitch/LightSwitchService/LightSwitchService.vcxproj.filters
@@ -39,6 +39,9 @@
     <ClCompile Include="NightLightRegistryObserver.cpp">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="trace.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="ThemeScheduler.h">
@@ -68,6 +71,9 @@
     <ClInclude Include="NightLightRegistryObserver.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="trace.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <Natvis Include="$(MSBuildThisFileDirectory)..\..\natvis\wil.natvis" />
diff --git a/src/modules/LightSwitch/LightSwitchService/LightSwitchSettings.cpp b/src/modules/LightSwitch/LightSwitchService/LightSwitchSettings.cpp
index 5221a197fe..488142b95b 100644
--- a/src/modules/LightSwitch/LightSwitchService/LightSwitchSettings.cpp
+++ b/src/modules/LightSwitch/LightSwitchService/LightSwitchSettings.cpp
@@ -5,6 +5,7 @@
 #include <filesystem>
 #include <fstream>
 #include <logger.h>
+#include <LightSwitchService/trace.h>
 
 using namespace std;
 
@@ -151,6 +152,7 @@ void LightSwitchSettings::LoadSettings()
             if (m_settings.scheduleMode != newMode)
             {
                 m_settings.scheduleMode = newMode;
+                Trace::LightSwitch::ScheduleModeToggled(val);
                 NotifyObservers(SettingId::ScheduleMode);
             }
         }
@@ -220,6 +222,8 @@ void LightSwitchSettings::LoadSettings()
             }
         }
 
+        bool themeTargetChanged = false;
+
         // ChangeSystem
         if (const auto jsonVal = values.get_bool_value(L"changeSystem"))
         {
@@ -227,6 +231,7 @@ void LightSwitchSettings::LoadSettings()
             if (m_settings.changeSystem != val)
             {
                 m_settings.changeSystem = val;
+                themeTargetChanged = true;
                 NotifyObservers(SettingId::ChangeSystem);
             }
         }
@@ -238,9 +243,16 @@ void LightSwitchSettings::LoadSettings()
             if (m_settings.changeApps != val)
             {
                 m_settings.changeApps = val;
+                themeTargetChanged = true;
                 NotifyObservers(SettingId::ChangeApps);
             }
         }
+
+        // For ChangeSystem/ChangeApps changes, log telemetry
+        if (themeTargetChanged)
+        {
+            Trace::LightSwitch::ThemeTargetChanged(m_settings.changeApps, m_settings.changeSystem);
+        }
     }
     catch (...)
     {
diff --git a/src/modules/LightSwitch/LightSwitchService/trace.cpp b/src/modules/LightSwitch/LightSwitchService/trace.cpp
new file mode 100644
index 0000000000..99afe7a95d
--- /dev/null
+++ b/src/modules/LightSwitch/LightSwitchService/trace.cpp
@@ -0,0 +1,43 @@
+#include "pch.h"
+#include "trace.h"
+
+// Telemetry strings should not be localized.
+#define LoggingProviderKey "Microsoft.PowerToys"
+
+TRACELOGGING_DEFINE_PROVIDER(
+    g_hProvider,
+    LoggingProviderKey,
+    // {38e8889b-9731-53f5-e901-e8a7c1753074}
+    (0x38e8889b, 0x9731, 0x53f5, 0xe9, 0x01, 0xe8, 0xa7, 0xc1, 0x75, 0x30, 0x74),
+    TraceLoggingOptionProjectTelemetry());
+
+void Trace::LightSwitch::RegisterProvider()
+{
+    TraceLoggingRegister(g_hProvider);
+}
+
+void Trace::LightSwitch::UnregisterProvider()
+{
+    TraceLoggingUnregister(g_hProvider);
+}
+
+void Trace::LightSwitch::ScheduleModeToggled(const std::wstring& newMode) noexcept
+{
+    TraceLoggingWriteWrapper(
+        g_hProvider,
+        "LightSwitch_ScheduleModeToggled",
+        ProjectTelemetryPrivacyDataTag(ProjectTelemetryTag_ProductAndServicePerformance),
+        TraceLoggingKeyword(PROJECT_KEYWORD_MEASURE),
+        TraceLoggingWideString(newMode.c_str(), "NewMode"));
+}
+
+void Trace::LightSwitch::ThemeTargetChanged(bool changeApps, bool changeSystem) noexcept
+{
+    TraceLoggingWriteWrapper(
+        g_hProvider,
+        "LightSwitch_ThemeTargetChanged",
+        ProjectTelemetryPrivacyDataTag(ProjectTelemetryTag_ProductAndServicePerformance),
+        TraceLoggingKeyword(PROJECT_KEYWORD_MEASURE),
+        TraceLoggingBoolean(changeApps, "ChangeApps"),
+        TraceLoggingBoolean(changeSystem, "ChangeSystem"));
+}
\ No newline at end of file
diff --git a/src/modules/LightSwitch/LightSwitchService/trace.h b/src/modules/LightSwitch/LightSwitchService/trace.h
new file mode 100644
index 0000000000..a06177075b
--- /dev/null
+++ b/src/modules/LightSwitch/LightSwitchService/trace.h
@@ -0,0 +1,17 @@
+#pragma once
+
+#include <common/Telemetry/TraceBase.h>
+#include <string>
+
+class Trace
+{
+public:
+    class LightSwitch : public telemetry::TraceBase
+    {
+    public:
+        static void RegisterProvider();
+        static void UnregisterProvider();
+        static void ScheduleModeToggled(const std::wstring& newMode) noexcept;
+        static void ThemeTargetChanged(bool changeApps, bool changeSystem) noexcept;
+    };
+};