#5856 An option to prevent hibernation

14 files changed, 578 insertions, 9 deletions

diff --git a/indra/newview/app_settings/settings.xml b/indra/newview/app_settings/settings.xml
index 8086afb865..b1e161182e 100644
--- a/indra/newview/app_settings/settings.xml
+++ b/indra/newview/app_settings/settings.xml
@@ -14429,6 +14429,17 @@
       <key>Value</key>
       <integer>180</integer>
     </map>
+    <key>OSHibernationMode</key>
+    <map>
+        <key>Comment</key>
+        <string>Whether to prevent OS from hibernating. 0 - can hibernate; 1 - can't hibernate, can turn screen off; 2 - can't hibernate, can't turn screen off </string>
+        <key>Persist</key>
+        <integer>1</integer>
+        <key>Type</key>
+        <string>S32</string>
+        <key>Value</key>
+        <integer>0</integer>
+    </map>
     <key>HeightUnits</key>
     <map>
       <key>Comment</key>
diff --git a/indra/newview/llagent.cpp b/indra/newview/llagent.cpp
index 31814d8f4f..35d60e6595 100644
--- a/indra/newview/llagent.cpp
+++ b/indra/newview/llagent.cpp
@@ -1552,6 +1552,8 @@ void LLAgent::setAFK()
         setControlFlags(AGENT_CONTROL_AWAY | AGENT_CONTROL_STOP);
         gAwayTimer.start();
     }
+
+    LLAppViewer::instance()->setPermitOSHibernation(true);
 }
 
 //-----------------------------------------------------------------------------
@@ -1570,6 +1572,13 @@ void LLAgent::clearAFK()
         sendAnimationRequest(ANIM_AGENT_AWAY, ANIM_REQUEST_STOP);
         clearControlFlags(AGENT_CONTROL_AWAY);
     }
+
+    if (isAgentAvatarValid())
+    {
+        // Only set this if agent is inworld, login screen
+        // shouldn't prevent hibernation.
+        LLAppViewer::instance()->setPermitOSHibernation(false);
+    }
 }
 
 //-----------------------------------------------------------------------------
diff --git a/indra/newview/llappviewer.cpp b/indra/newview/llappviewer.cpp
index 6b5c0ea6b0..4a6739bb40 100644
--- a/indra/newview/llappviewer.cpp
+++ b/indra/newview/llappviewer.cpp
@@ -633,6 +633,12 @@ bool LLAppViewer::sendURLToOtherInstance(const std::string& url)
     return false;
 }
 
+//virtual
+void LLAppViewer::setOSHibernationMode(eHibernationMode mode)
+{
+    // See OS specific files
+}
+
 //----------------------------------------------------------------------------
 // LLAppViewer definition
 
@@ -4474,9 +4480,12 @@ void LLAppViewer::abortQuit()
     mClosingFloaters = false;
 }
 
-void LLAppViewer::sendViewerStatistics()
+void LLAppViewer::sendViewerStatistics(bool include_preferences)
 {
-    send_viewer_stats(false);
+    if (!gDisconnected)
+    {
+        send_viewer_stats(include_preferences);
+    }
 }
 
 void LLAppViewer::migrateCacheDirectory()
@@ -5857,6 +5866,29 @@ void LLAppViewer::outOfMemorySoftQuit()
     }
 }
 
+void LLAppViewer::setPermitOSHibernation(bool permit)
+{
+    if (permit)
+    {
+        if (mCurrentHibernationMode != LL_HIBERNATE_MODE_DEFAULT)
+        {
+            // Will call OS specific code to let OS hibernate when idle
+            setOSHibernationMode(LL_HIBERNATE_MODE_DEFAULT);
+            mCurrentHibernationMode = LL_HIBERNATE_MODE_DEFAULT;
+        }
+    }
+    else
+    {
+        static LLCachedControl<S32> os_hibernation_mode(gSavedSettings, "OSHibernationMode", 0);
+        eHibernationMode mode = static_cast<eHibernationMode>(os_hibernation_mode());
+        if (mode != LL_HIBERNATE_MODE_DEFAULT && mCurrentHibernationMode != mode)
+        {
+            setOSHibernationMode(mode);
+            mCurrentHibernationMode = mode;
+        }
+    }
+}
+
 void LLAppViewer::idleNameCache()
 {
     // Neither old nor new name cache can function before agent has a region
@@ -6064,6 +6096,9 @@ void LLAppViewer::disconnectViewer()
     // Pass the connection state to LLUrlEntryParcel not to attempt
     // parcel info requests while disconnected.
     LLUrlEntryParcel::setDisconnected(gDisconnected);
+
+    // Restore default OS hibernation mode
+    setPermitOSHibernation(true);
 }
 
 void LLAppViewer::forceErrorLLError()
@@ -6329,6 +6364,15 @@ void LLAppViewer::handleLoginComplete()
     // we logged in successfully, so save settings on logout
     LL_INFOS() << "Login successful, per account settings will be saved on log out." << LL_ENDL;
     mSavePerAccountSettings=true;
+
+    // Don't allow hibernation while we're running
+    setPermitOSHibernation(false);
+    // Track 'hibernation' mode changes
+    mOSHibernationModeChangeConnection = gSavedSettings.getControl("OSHibernationMode")->getSignal()->connect([](LLControlVariable* control, const LLSD& new_val, const LLSD& old_val)
+    {
+        // setPermitOSHibernation will sort itself out based on new mode.
+        LLAppViewer::instance()->setPermitOSHibernation(false);
+    });
 }
 
 //virtual
diff --git a/indra/newview/llappviewer.h b/indra/newview/llappviewer.h
index cde58b0850..6ecafae036 100644
--- a/indra/newview/llappviewer.h
+++ b/indra/newview/llappviewer.h
@@ -114,7 +114,7 @@ public:
                    const LLSD& substitutions = LLSD()); // Display an error dialog and forcibly quit.
     void earlyExitNoNotify(); // Do not display error dialog then forcibly quit.
     void abortQuit();  // Called to abort a quit request.
-    void sendViewerStatistics();
+    void sendViewerStatistics(bool include_preferences);
 
     bool quitRequested() { return mQuitRequested; }
     bool logoutRequestSent() { return mLogoutRequestSent; }
@@ -269,6 +269,8 @@ public:
     // Note: mQuitRequested can be aborted by user.
     void outOfMemorySoftQuit();
 
+    virtual void setPermitOSHibernation(bool permit);
+
 #ifdef LL_DISCORD
     static void initDiscordSocial();
     static void updateDiscordActivity();
@@ -285,6 +287,14 @@ protected:
     virtual bool initSLURLHandler();
     virtual bool sendURLToOtherInstance(const std::string& url);
 
+    typedef enum
+    {
+        LL_HIBERNATE_MODE_DEFAULT = 0, // Use the platform's default behavior.
+        LL_HIBERNATE_MODE_PREVENT = 1,
+        LL_HIBERNATE_MODE_PREVENT_SCREEN = 2,
+    } eHibernationMode;
+    virtual void setOSHibernationMode(eHibernationMode mode);
+
     virtual bool initParseCommandLine(LLCommandLineParser& clp)
         { return true; } // Allow platforms to specify the command line args.
 
@@ -391,6 +401,9 @@ private:
     LLAppCoreHttp mAppCoreHttp;
 
     bool mIsFirstRun;
+
+    eHibernationMode mCurrentHibernationMode = LL_HIBERNATE_MODE_DEFAULT;
+    boost::signals2::scoped_connection mOSHibernationModeChangeConnection;
 };
 
 // Globals with external linkage. From viewer.h
diff --git a/indra/newview/llappviewerlinux.cpp b/indra/newview/llappviewerlinux.cpp
index 89d19d180b..fe0d6f6e7d 100644
--- a/indra/newview/llappviewerlinux.cpp
+++ b/indra/newview/llappviewerlinux.cpp
@@ -58,6 +58,10 @@ namespace
     void (*gOldTerminateHandler)() = NULL;
 }
 
+// Initialize static members
+guint32 LLAppViewerLinux::sPowerInhibitCookie = 0;
+bool LLAppViewerLinux::sPowerInhibitActive = false;
+
 
 static void exceptionTerminateHandler()
 {
@@ -117,6 +121,11 @@ LLAppViewerLinux::LLAppViewerLinux()
 
 LLAppViewerLinux::~LLAppViewerLinux()
 {
+    // Clean up any power management inhibition on exit
+    if (sPowerInhibitActive)
+    {
+        uninhibitPowerManagement();
+    }
 }
 
 bool LLAppViewerLinux::init()
@@ -329,6 +338,299 @@ bool LLAppViewerLinux::sendURLToOtherInstance(const std::string& url)
 }
 #endif // LL_DBUS_ENABLED
 
+
+void LLAppViewerLinux::setOSHibernationMode(eHibernationMode mode)
+{
+    if (mode == LL_HIBERNATE_MODE_DEFAULT)
+    {
+        // Allow OS to sleep/hibernate - remove any inhibition
+        if (sPowerInhibitActive)
+        {
+            uninhibitPowerManagement();
+            LL_INFOS("OS") << "Permitted OS hibernation/sleep" << LL_ENDL;
+        }
+    }
+    else if (mode == LL_HIBERNATE_MODE_PREVENT)
+    {
+        // Prevent system sleep, but allow display to turn off
+        // Release any existing inhibition first to allow mode switching
+        if (sPowerInhibitActive)
+        {
+            uninhibitPowerManagement();
+        }
+
+        if (inhibitPowerManagement(false))
+        {
+            LL_INFOS("OS") << "Prevented OS hibernation/sleep, display sleep allowed" << LL_ENDL;
+        }
+        else
+        {
+            LL_WARNS("OS") << "Failed to prevent OS hibernation/sleep" << LL_ENDL;
+        }
+    }
+    else if (mode == LL_HIBERNATE_MODE_PREVENT_SCREEN)
+    {
+        // Prevent both system and display sleep
+        // Release any existing inhibition first to allow mode switching
+        if (sPowerInhibitActive)
+        {
+            uninhibitPowerManagement();
+        }
+
+        if (inhibitPowerManagement(true))
+        {
+            LL_INFOS("OS") << "Prevented OS hibernation/sleep and display sleep" << LL_ENDL;
+        }
+        else
+        {
+            LL_WARNS("OS") << "Failed to prevent OS hibernation/sleep and display sleep" << LL_ENDL;
+        }
+    }
+}
+
+// TODO: This is AI Generated!!!, needs review and testing.
+bool LLAppViewerLinux::inhibitPowerManagement(bool inhibit_display)
+{
+#if LL_DBUS_ENABLED
+    // Try to use D-Bus to inhibit power management via various desktop environment APIs
+    // This works with GNOME, KDE, XFCE, and most modern Linux desktop environments
+
+    if (!grab_dbus_syms(DBUSGLIB_DYLIB_DEFAULT_NAME))
+    {
+        LL_WARNS("OS") << "Failed to load D-Bus symbols for power management" << LL_ENDL;
+        return false;
+    }
+
+    GError* error = nullptr;
+    DBusGConnection* bus = lldbus_g_bus_get(DBUS_BUS_SESSION, &error);
+
+    if (!bus)
+    {
+        LL_WARNS("OS") << "Failed to connect to D-Bus session bus: "
+            << (error ? error->message : "unknown error") << LL_ENDL;
+        if (error)
+            g_error_free(error);
+        return false;
+    }
+
+    // Try multiple power management services in order of preference
+    // 1. org.freedesktop.PowerManagement (older standard)
+    // 2. org.gnome.SessionManager (GNOME)
+    // 3. org.kde.Solid.PowerManagement (KDE)
+
+    const char* services[] = {
+        "org.freedesktop.PowerManagement",
+        "org.gnome.SessionManager",
+        "org.kde.Solid.PowerManagement"
+    };
+
+    const char* paths[] = {
+        "/org/freedesktop/PowerManagement/Inhibit",
+        "/org/gnome/SessionManager",
+        "/org/kde/Solid/PowerManagement"
+    };
+
+    const char* interfaces[] = {
+        "org.freedesktop.PowerManagement.Inhibit",
+        "org.gnome.SessionManager",
+        "org.kde.Solid.PowerManagement"
+    };
+
+    const char* methods[] = {
+        "Inhibit",
+        "Inhibit",
+        "inhibit"
+    };
+
+    bool success = false;
+
+    for (int i = 0; i < 3 && !success; ++i)
+    {
+        DBusGProxy* proxy = lldbus_g_proxy_new_for_name(
+            bus,
+            services[i],
+            paths[i],
+            interfaces[i]
+        );
+
+        if (!proxy)
+            continue;
+
+        error = nullptr;
+        guint32 cookie = 0;
+
+        if (i == 0) // freedesktop.PowerManagement
+        {
+            // Inhibit(application_name: s, reason: s) -> cookie: u
+            success = lldbus_g_proxy_call(
+                proxy,
+                methods[i],
+                &error,
+                G_TYPE_STRING, "Second Life Viewer",
+                G_TYPE_STRING, inhibit_display ?
+                "Viewer active - preventing system and display sleep" :
+                "Viewer active - preventing system sleep",
+                G_TYPE_INVALID,
+                G_TYPE_UINT, &cookie,
+                G_TYPE_INVALID
+            );
+        }
+        else if (i == 1) // GNOME SessionManager
+        {
+            // Inhibit(app_id: s, toplevel_xid: u, reason: s, flags: u) -> cookie: u
+            // flags: 4 = suspend, 8 = idle (display), 12 = both
+            guint32 flags = inhibit_display ? 12 : 4;
+            success = lldbus_g_proxy_call(
+                proxy,
+                methods[i],
+                &error,
+                G_TYPE_STRING, "SecondLifeViewer",
+                G_TYPE_UINT, 0,  // toplevel_xid (0 = none)
+                G_TYPE_STRING, inhibit_display ?
+                "Viewer active - preventing system and display sleep" :
+                "Viewer active - preventing system sleep",
+                G_TYPE_UINT, flags,
+                G_TYPE_INVALID,
+                G_TYPE_UINT, &cookie,
+                G_TYPE_INVALID
+            );
+        }
+        else if (i == 2) // KDE Solid
+        {
+            // Different method signature for KDE
+            success = lldbus_g_proxy_call(
+                proxy,
+                methods[i],
+                &error,
+                G_TYPE_INVALID,
+                G_TYPE_INT, &cookie,
+                G_TYPE_INVALID
+            );
+        }
+
+        if (success)
+        {
+            sPowerInhibitCookie = cookie;
+            sPowerInhibitActive = true;
+            LL_INFOS("OS") << "Successfully inhibited power management using "
+                << services[i] << LL_ENDL;
+        }
+        else if (error)
+        {
+            LL_DEBUGS("OS") << "Failed to inhibit via " << services[i]
+                << ": " << error->message << LL_ENDL;
+            g_error_free(error);
+            error = nullptr;
+        }
+
+        g_object_unref(proxy);
+    }
+
+    return success;
+
+#else // !LL_DBUS_ENABLED
+    LL_WARNS("OS") << "Power management control not available - D-Bus support not enabled" << LL_ENDL;
+    return false;
+#endif
+}
+
+void LLAppViewerLinux::uninhibitPowerManagement()
+{
+#if LL_DBUS_ENABLED
+    if (!sPowerInhibitActive || sPowerInhibitCookie == 0)
+    {
+        return;
+    }
+
+    if (!grab_dbus_syms(DBUSGLIB_DYLIB_DEFAULT_NAME))
+    {
+        LL_WARNS("OS") << "Failed to load D-Bus symbols for power management uninhibit" << LL_ENDL;
+        return;
+    }
+
+    GError* error = nullptr;
+    DBusGConnection* bus = lldbus_g_bus_get(DBUS_BUS_SESSION, &error);
+
+    if (!bus)
+    {
+        if (error)
+            g_error_free(error);
+        return;
+    }
+
+    // Try to uninhibit using all services that might have been used
+    const char* services[] = {
+        "org.freedesktop.PowerManagement",
+        "org.gnome.SessionManager",
+        "org.kde.Solid.PowerManagement"
+    };
+
+    const char* paths[] = {
+        "/org/freedesktop/PowerManagement/Inhibit",
+        "/org/gnome/SessionManager",
+        "/org/kde/Solid/PowerManagement"
+    };
+
+    const char* interfaces[] = {
+        "org.freedesktop.PowerManagement.Inhibit",
+        "org.gnome.SessionManager",
+        "org.kde.Solid.PowerManagement"
+    };
+
+    const char* methods[] = {
+        "UnInhibit",
+        "Uninhibit",
+        "uninhibit"
+    };
+
+    bool success = false;
+
+    for (int i = 0; i < 3; ++i)
+    {
+        DBusGProxy* proxy = lldbus_g_proxy_new_for_name(
+            bus,
+            services[i],
+            paths[i],
+            interfaces[i]
+        );
+
+        if (!proxy)
+            continue;
+
+        error = nullptr;
+
+        if (lldbus_g_proxy_call(
+            proxy,
+            methods[i],
+            &error,
+            G_TYPE_UINT, sPowerInhibitCookie,
+            G_TYPE_INVALID,
+            G_TYPE_INVALID))
+        {
+            success = true;
+            LL_INFOS("OS") << "Successfully uninhibited power management using "
+                << services[i] << LL_ENDL;
+        }
+        else if (error)
+        {
+            LL_DEBUGS("OS") << "Failed to uninhibit via " << services[i]
+                << ": " << error->message << LL_ENDL;
+            g_error_free(error);
+            error = nullptr;
+        }
+
+        g_object_unref(proxy);
+
+        if (success)
+            break;
+    }
+
+    sPowerInhibitCookie = 0;
+    sPowerInhibitActive = false;
+
+#endif // LL_DBUS_ENABLED
+}
+
 void LLAppViewerLinux::initCrashReporting(bool reportFreeze)
 {
     std::string cmd =gDirUtilp->getExecutableDir();
diff --git a/indra/newview/llappviewerlinux.h b/indra/newview/llappviewerlinux.h
index dde223878d..6ab3682515 100644
--- a/indra/newview/llappviewerlinux.h
+++ b/indra/newview/llappviewerlinux.h
@@ -68,6 +68,16 @@ protected:
 
     virtual bool initSLURLHandler();
     virtual bool sendURLToOtherInstance(const std::string& url);
+    virtual void setOSHibernationMode(eHibernationMode mode);
+
+private:
+    // Power management state tracking
+    static guint32 sPowerInhibitCookie;
+    static bool sPowerInhibitActive;
+
+    // Helper methods for power management
+    bool inhibitPowerManagement(bool inhibit_display);
+    void uninhibitPowerManagement();
 };
 
 #if LL_DBUS_ENABLED
diff --git a/indra/newview/llappviewermacosx-objc.h b/indra/newview/llappviewermacosx-objc.h
index bfbb48dadb..13b8056193 100644
--- a/indra/newview/llappviewermacosx-objc.h
+++ b/indra/newview/llappviewermacosx-objc.h
@@ -32,5 +32,6 @@
 
 void force_ns_sxeption();
 void register_url_schemes();
+void set_os_hibernation_mode(int mode);
 
 #endif // LL_LLAPPVIEWERMACOSX_OBJC_H
diff --git a/indra/newview/llappviewermacosx-objc.mm b/indra/newview/llappviewermacosx-objc.mm
index 75d6b56e3e..ab4ae428b9 100644
--- a/indra/newview/llappviewermacosx-objc.mm
+++ b/indra/newview/llappviewermacosx-objc.mm
@@ -29,6 +29,7 @@
 #endif
 
 #import <Cocoa/Cocoa.h>
+#import <IOKit/pwr_mgt/IOPMLib.h>
 #include <iostream>
 
 #include "llappviewermacosx-objc.h"
@@ -63,3 +64,68 @@ void register_url_schemes()
         }
     }
 }
+
+// Add these as static variables at file scope
+static IOPMAssertionID gPowerAssertionID = kIOPMNullAssertionID;
+
+void set_os_hibernation_mode(int mode)
+{
+    // Release existing assertion
+    if (gPowerAssertionID != kIOPMNullAssertionID)
+    {
+        IOReturn result = IOPMAssertionRelease(gPowerAssertionID);
+        if (result == kIOReturnSuccess)
+        {
+            gPowerAssertionID = kIOPMNullAssertionID;
+            NSLog(@"Permitted OS hibernation/sleep");
+        }
+        else
+        {
+            NSLog(@"Failed to release power assertion: %d", result);
+        }
+    }
+
+    if (mode == 1)
+    {
+        // Prevent OS from sleeping/hibernating
+        CFStringRef assertionName = CFSTR("Second Life Viewer");
+        // kIOPMAssertionTypeNoIdleSleep prevents idle sleep
+        IOReturn result = IOPMAssertionCreateWithName(
+            kIOPMAssertionTypeNoIdleSleep,
+            kIOPMAssertionLevelOn,
+            assertionName,
+            &gPowerAssertionID
+        );
+
+         if (result == kIOReturnSuccess)
+        {
+            NSLog(@"Prevented OS hibernation/sleep, allow display sleep");
+        }
+        else
+        {
+            NSLog(@"Failed to create power assertion: %d", result);
+        }
+    }
+    else if (mode == 2)
+    {
+        // Prevent OS from sleeping/hibernating, prevent screen from going off
+        CFStringRef assertionName = CFSTR("Second Life Viewer");
+        // kIOPMAssertionTypeNoIdleSleep prevents idle sleep
+        // kIOPMAssertionTypeNoDisplaySleep prevents display sleep
+        IOReturn result = IOPMAssertionCreateWithName(
+            kIOPMAssertionTypeNoDisplaySleep,
+            kIOPMAssertionLevelOn,
+            assertionName,
+            &gPowerAssertionID
+        );
+
+        if (result == kIOReturnSuccess)
+        {
+            NSLog(@"Prevented OS hibernation/sleep or screen from turning off");
+        }
+        else
+        {
+            NSLog(@"Failed to create power assertion: %d", result);
+        }
+    }
+}
diff --git a/indra/newview/llappviewermacosx.cpp b/indra/newview/llappviewermacosx.cpp
index 830e2d4473..1c01d06852 100644
--- a/indra/newview/llappviewermacosx.cpp
+++ b/indra/newview/llappviewermacosx.cpp
@@ -125,6 +125,7 @@ bool pumpMainLoop()
 
 void cleanupViewer()
 {
+    set_os_hibernation_mode(0); // restore default OS hibernation behavior
     if(!LLApp::isError())
     {
         if (gViewerAppPtr)
@@ -427,6 +428,12 @@ bool LLAppViewerMacOSX::initSLURLHandler()
     return true;
 }
 
+void LLAppViewerMacOSX::setOSHibernationMode(eHibernationMode mode)
+{
+    // pass to objective-c++
+    set_os_hibernation_mode((int)mode);
+}
+
 std::string LLAppViewerMacOSX::generateSerialNumber()
 {
     char serial_md5[MD5HEX_STR_SIZE];       // Flawfinder: ignore
diff --git a/indra/newview/llappviewermacosx.h b/indra/newview/llappviewermacosx.h
index 35fc99dbd9..1153bd4191 100644
--- a/indra/newview/llappviewermacosx.h
+++ b/indra/newview/llappviewermacosx.h
@@ -47,6 +47,7 @@ public:
 protected:
     virtual bool restoreErrorTrap();
     virtual bool initSLURLHandler();
+    virtual void setOSHibernationMode(eHibernationMode mode);
 
     std::string generateSerialNumber();
     virtual bool initParseCommandLine(LLCommandLineParser& clp);
diff --git a/indra/newview/llappviewerwin32.cpp b/indra/newview/llappviewerwin32.cpp
index 5184b0f025..25aeb2a26e 100644
--- a/indra/newview/llappviewerwin32.cpp
+++ b/indra/newview/llappviewerwin32.cpp
@@ -1020,6 +1020,56 @@ bool LLAppViewerWin32::sendURLToOtherInstance(const std::string& url)
     return false;
 }
 
+void LLAppViewerWin32::setOSHibernationMode(eHibernationMode mode)
+{
+    // ES_CONTINUOUS tells Windows to reset the idle timer
+    // and restore normal operation
+    // ES_SYSTEM_REQUIRED prevents system sleep/hibernation
+    // ES_DISPLAY_REQUIRED prevents display sleep
+
+    if (mode == LL_HIBERNATE_MODE_DEFAULT)
+    {
+        // Allow OS to hibernate - clear the previous execution state flags
+        // ES_CONTINUOUS without other flags allows the system to idle normally
+        SetThreadExecutionState(ES_CONTINUOUS);
+        LL_INFOS("OS") << "Permitted OS hibernation/sleep" << LL_ENDL;
+    }
+    else if (mode == LL_HIBERNATE_MODE_PREVENT)
+    {
+        // Prevent OS from hibernating while viewer is running
+        // ES_CONTINUOUS | ES_SYSTEM_REQUIRED keeps the system awake
+        EXECUTION_STATE result = SetThreadExecutionState(
+            ES_CONTINUOUS | ES_SYSTEM_REQUIRED
+        );
+        if (result == NULL)
+        {
+            LL_WARNS("OS") << "Failed to prevent OS hibernation, error: " << GetLastError() << LL_ENDL;
+        }
+        else
+        {
+            LL_INFOS("OS") << "Prevented OS hibernation, but allowed display sleep" << LL_ENDL;
+        }
+    }
+    else if (mode == LL_HIBERNATE_MODE_PREVENT_SCREEN)
+    {
+        // Prevent OS from hibernating or turning screen off while viewer is running
+        // ES_CONTINUOUS | ES_SYSTEM_REQUIRED keeps the system awake
+        // ES_DISPLAY_REQUIRED keeps the display on
+        EXECUTION_STATE result = SetThreadExecutionState(
+            ES_CONTINUOUS | ES_SYSTEM_REQUIRED | ES_DISPLAY_REQUIRED
+        );
+
+        if (result == NULL)
+        {
+            LL_WARNS("OS") << "Failed to prevent OS hibernation and display sleep, error: " << GetLastError() << LL_ENDL;
+        }
+        else
+        {
+            LL_INFOS("OS") << "Prevented OS hibernation/sleep" << LL_ENDL;
+        }
+    }
+}
+
 bool LLAppViewerWin32::sendShutdownToOtherInstances(const std::wstring& install_dir)
 {
     // Velopack installs viewer like this:
diff --git a/indra/newview/llappviewerwin32.h b/indra/newview/llappviewerwin32.h
index 971907694a..7c3c7a475a 100644
--- a/indra/newview/llappviewerwin32.h
+++ b/indra/newview/llappviewerwin32.h
@@ -62,6 +62,7 @@ protected:
     bool restoreErrorTrap() override;
 
     bool sendURLToOtherInstance(const std::string& url) override;
+    void setOSHibernationMode(eHibernationMode mode) override;
 
     std::string generateSerialNumber();
 
diff --git a/indra/newview/llviewerwindow.cpp b/indra/newview/llviewerwindow.cpp
index abd7096f50..4229ffcfb5 100644
--- a/indra/newview/llviewerwindow.cpp
+++ b/indra/newview/llviewerwindow.cpp
@@ -1487,12 +1487,30 @@ void LLViewerWindow::handleCloseRequestCanceled()
 
 void LLViewerWindow::handleSuspendRequest()
 {
-    LLAppViewer::instance()->sendViewerStatistics();
-    // Todo: this should send a disconnect request as viewer
-    // can't keep heartbeat up while suspended and will get
-    // disconnected within a minute.
-    // Add a disconnect here once 'prevent OS from sleeping'
-    // feature is ready.
+    static LLCachedControl<S32> os_hibernation_mode(gSavedSettings, "OSHibernationMode", 0);
+    if (os_hibernation_mode == 0)
+    {
+        LL_INFOS() << "Got a 'suspend' event from OS" << LL_ENDL;
+        // Viewer doesn't handle hibernation.
+        // Just send statistics.
+        LLAppViewer::instance()->sendViewerStatistics(false);
+    }
+    else
+    {
+        LL_INFOS() << "Got a 'suspend' event from OS, disconnecting" << LL_ENDL;
+        // Viewer is set to prevent hibernation if agent isn't away.
+        // If we got here, likely Agent 'went' away then viewer got
+        // a hibernation message.
+        // We have a limited timeframe. Sends stats then disconnect.
+        LLViewerRegion* region = gAgent.getRegion();
+        if (region)
+        {
+            LLAppViewer::instance()->sendViewerStatistics(true);
+            LLAppViewer::instance()->metricsSend(!gDisconnected);
+            // Make sure to show a message.
+            LLAppViewer::instance()->forceDisconnect(LLTrans::getString("YouHaveBeenDisconnected"));
+        }
+    }
 }
 
 bool LLViewerWindow::handleCloseRequest(LLWindow *window, bool from_user)
diff --git a/indra/newview/skins/default/xui/en/panel_preferences_setup.xml b/indra/newview/skins/default/xui/en/panel_preferences_setup.xml
index 2036ed75ca..d5f2f69df7 100644
--- a/indra/newview/skins/default/xui/en/panel_preferences_setup.xml
+++ b/indra/newview/skins/default/xui/en/panel_preferences_setup.xml
@@ -246,5 +246,41 @@
     <button.commit_callback
 		  function="Pref.Proxy" />
   </button>
+  <text
+     type="string"
+     length="1"
+     follows="left|top"
+     height="10"
+     layout="topleft"
+     left="30"
+     name="os_hibernation_mode"
+     mouse_opaque="false"
+     top_pad="8"
+     width="300">
+    Prevent OS from hibernating if not Away:
+  </text>
+  <combo_box
+     control_name="OSHibernationMode"
+     follows="left|top"
+     height="23"
+     layout="topleft"
+     left_delta="50"
+     top_pad="10"
+     name="os_hibernation_combobox"
+     width="300"
+     tool_tip="Only prevents OS from sleeping if user is not away">
+        <combo_box.item
+         label="Can hibernate"
+         name="can_hibernate"
+         value="0" />
+        <combo_box.item
+         label="Can't hibernate, can turn screen off"
+         name="cant_hibernate"
+         value="1" />
+        <combo_box.item
+         label="Can't hibernate, can't turn screen off"
+         name="cant_hibernate_screen"
+         value="2" />
+  </combo_box>
 </panel>