Add support for OSC777 (Send Notification) (#20012)

## Summary of the Pull Request
targets #20010

This adds support for the `OSC 777 ; notify ; title ; body ST` sequence.
This allows client applications to send a notification to the Terminal.
When this notification is clicked, it summons the terminal window that
sent it.

## Validation Steps Performed
```pwsh
# in PowerShell. Terminal should not be focused.
sleep 2; Write-Output "`e]777;notify;Hello;This is a notification`a"
```

## PR Checklist
- [X] Closes #7718
- [ ] Documentation updated
- [X] Schema updated (if necessary)

Heavily based on #19938
Co-authored by @zadjii-msft

.github/actions/spelling/expect/expect.txt

@@ -1758,6 +1758,7 @@ UPKEY
 upss
 uregex
 URegular
+urxvt
 usebackq
 USECALLBACK
 USECOLOR

doc/cascadia/profiles.schema.json

@@ -2794,6 +2794,11 @@
           "description": "When set to true, VT applications will be allowed to set the contents of the local clipboard using OSC 52 (Manipulate Selection Data).",
           "type": "boolean"
         },
+        "compatibility.allowOSC777": {
+          "default": false,
+          "description": "When set to true, applications can send OSC 777 escape sequences to trigger desktop toast notifications with a custom title and body.",
+          "type": "boolean"
+        },
         "unfocusedAppearance": {
           "$ref": "#/$defs/AppearanceConfig",
           "description": "Sets the appearance of the terminal when it is unfocused.",

src/cascadia/TerminalApp/DesktopNotification.cpp

@@ -91,7 +91,7 @@ namespace winrt::TerminalApp::implementation
             // When the user activates (clicks) the toast, fire the callback.
             if (activatedFunc)
             {
-                toast.Activated([activatedFunc](const auto& /*sender*/, const auto& /*eventArgs*/) {
+                toast.Activated([activatedFunc = std::move(activatedFunc)](const auto& /*sender*/, const auto& /*eventArgs*/) {
                     activatedFunc();
                 });
             }

src/cascadia/TerminalApp/TabManagement.cpp

@@ -1353,7 +1353,11 @@ namespace winrt::TerminalApp::implementation
         // Use the Tab object's identity hash as a stable toast tag.
         // This survives tab reordering and cross-window moves.
         const auto tabHash = std::hash<winrt::Windows::Foundation::IUnknown>{}(*tab);
+#ifdef _WIN64
         const hstring tabTag{ fmt::format(FMT_COMPILE(L"wt-tab-{:016x}"), tabHash) };
+#else
+        const hstring tabTag{ fmt::format(FMT_COMPILE(L"wt-tab-{:08x}"), tabHash) };
+#endif
 
         const implementation::DesktopNotificationArgs args{
             .Title = notificationTitle,

src/cascadia/TerminalApp/TerminalPaneContent.cpp

@@ -42,6 +42,7 @@ namespace winrt::TerminalApp::implementation
         _controlEvents._SetTaskbarProgress = _control.SetTaskbarProgress(winrt::auto_revoke, { get_weak(), &TerminalPaneContent::_controlSetTaskbarProgress });
         _controlEvents._ReadOnlyChanged = _control.ReadOnlyChanged(winrt::auto_revoke, { get_weak(), &TerminalPaneContent::_controlReadOnlyChanged });
         _controlEvents._FocusFollowMouseRequested = _control.FocusFollowMouseRequested(winrt::auto_revoke, { get_weak(), &TerminalPaneContent::_controlFocusFollowMouseRequested });
+        _controlEvents._ShowNotification = _control.ShowNotification(winrt::auto_revoke, { get_weak(), &TerminalPaneContent::_controlShowNotification });
     }
     void TerminalPaneContent::_removeControlEvents()
     {
@@ -170,6 +171,11 @@ namespace winrt::TerminalApp::implementation
         FocusRequested.raise(*this, nullptr);
     }
 
+    void TerminalPaneContent::_controlShowNotification(const IInspectable& /*sender*/, const ShowNotificationEventArgs& args)
+    {
+        NotificationRequested.raise(*this, winrt::make<implementation::NotificationEventArgs>(args.Title(), args.Body()));
+    }
+
     // Method Description:
     // - Called when our attached control is closed. Triggers listeners to our close
     //   event, if we're a leaf pane.

src/cascadia/TerminalApp/TerminalPaneContent.h

@@ -88,6 +88,7 @@ namespace winrt::TerminalApp::implementation
             winrt::Microsoft::Terminal::Control::TermControl::SetTaskbarProgress_revoker _SetTaskbarProgress;
             winrt::Microsoft::Terminal::Control::TermControl::ReadOnlyChanged_revoker _ReadOnlyChanged;
             winrt::Microsoft::Terminal::Control::TermControl::FocusFollowMouseRequested_revoker _FocusFollowMouseRequested;
+            winrt::Microsoft::Terminal::Control::TermControl::ShowNotification_revoker _ShowNotification;
 
         } _controlEvents;
         void _setupControlEvents();
@@ -103,6 +104,7 @@ namespace winrt::TerminalApp::implementation
         void _controlSetTaskbarProgress(const winrt::Windows::Foundation::IInspectable& sender, const winrt::Windows::Foundation::IInspectable& args);
         void _controlReadOnlyChanged(const winrt::Windows::Foundation::IInspectable& sender, const winrt::Windows::Foundation::IInspectable& args);
         void _controlFocusFollowMouseRequested(const winrt::Windows::Foundation::IInspectable& sender, const winrt::Windows::Foundation::IInspectable& args);
+        void _controlShowNotification(const winrt::Windows::Foundation::IInspectable& sender, const winrt::Microsoft::Terminal::Control::ShowNotificationEventArgs& args);
 
         void _closeTerminalRequestedHandler(const winrt::Windows::Foundation::IInspectable& sender, const winrt::Windows::Foundation::IInspectable& /*args*/);
         void _restartTerminalRequestedHandler(const winrt::Windows::Foundation::IInspectable& sender, const winrt::Windows::Foundation::IInspectable& /*args*/);

src/cascadia/TerminalControl/ControlCore.cpp

@@ -139,6 +139,9 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         auto pfnSearchMissingCommand = [this](auto&& PH1, auto&& PH2) { _terminalSearchMissingCommand(std::forward<decltype(PH1)>(PH1), std::forward<decltype(PH2)>(PH2)); };
         _terminal->SetSearchMissingCommandCallback(pfnSearchMissingCommand);
 
+        auto pfnShowNotification = [this](auto&& PH1, auto&& PH2) { _terminalShowNotification(std::forward<decltype(PH1)>(PH1), std::forward<decltype(PH2)>(PH2)); };
+        _terminal->SetShowNotificationCallback(pfnShowNotification);
+
         auto pfnClearQuickFix = [this] { ClearQuickFix(); };
         _terminal->SetClearQuickFixCallback(pfnClearQuickFix);
 
@@ -1692,6 +1695,11 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         SearchMissingCommand.raise(*this, make<implementation::SearchMissingCommandEventArgs>(hstring{ missingCommand }, bufferRow));
     }
 
+    void ControlCore::_terminalShowNotification(std::wstring_view title, std::wstring_view body)
+    {
+        ShowNotification.raise(*this, make<implementation::ShowNotificationEventArgs>(hstring{ title }, hstring{ body }));
+    }
+
     void ControlCore::OpenCWD()
     {
         const auto workingDirectory = WorkingDirectory();

src/cascadia/TerminalControl/ControlCore.h

@@ -292,6 +292,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         til::typed_event<IInspectable, Control::OpenHyperlinkEventArgs> OpenHyperlink;
         til::typed_event<IInspectable, Control::CompletionsChangedEventArgs> CompletionsChanged;
         til::typed_event<IInspectable, Control::SearchMissingCommandEventArgs> SearchMissingCommand;
+        til::typed_event<IInspectable, Control::ShowNotificationEventArgs> ShowNotification;
         til::typed_event<> RefreshQuickFixUI;
         til::typed_event<IInspectable, Control::WindowSizeChangedEventArgs> WindowSizeChanged;
 
@@ -333,6 +334,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
                                    const int velocity,
                                    const std::chrono::microseconds duration);
         void _terminalSearchMissingCommand(std::wstring_view missingCommand, const til::CoordType& bufferRow);
+        void _terminalShowNotification(std::wstring_view title, std::wstring_view body);
         void _terminalWindowSizeChanged(int32_t width, int32_t height);
 
         void _terminalCompletionsChanged(std::wstring_view menuJson, unsigned int replaceLength);

src/cascadia/TerminalControl/ControlCore.idl

@@ -198,6 +198,7 @@ namespace Microsoft.Terminal.Control
         event Windows.Foundation.TypedEventHandler<Object, Object> RendererEnteredErrorState;
         event Windows.Foundation.TypedEventHandler<Object, ShowWindowArgs> ShowWindowChanged;
         event Windows.Foundation.TypedEventHandler<Object, SearchMissingCommandEventArgs> SearchMissingCommand;
+        event Windows.Foundation.TypedEventHandler<Object, ShowNotificationEventArgs> ShowNotification;
         event Windows.Foundation.TypedEventHandler<Object, Object> RefreshQuickFixUI;
         event Windows.Foundation.TypedEventHandler<Object, WindowSizeChangedEventArgs> WindowSizeChanged;
 

src/cascadia/TerminalControl/EventArgs.h

@@ -20,6 +20,7 @@
 #include "CharSentEventArgs.g.h"
 #include "StringSentEventArgs.g.h"
 #include "SearchMissingCommandEventArgs.g.h"
+#include "ShowNotificationEventArgs.g.h"
 #include "WindowSizeChangedEventArgs.g.h"
 
 namespace winrt::Microsoft::Terminal::Control::implementation
@@ -252,6 +253,17 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         til::property<til::CoordType> BufferRow;
     };
 
+    struct ShowNotificationEventArgs : public ShowNotificationEventArgsT<ShowNotificationEventArgs>
+    {
+    public:
+        ShowNotificationEventArgs(const winrt::hstring& title, const winrt::hstring& body) :
+            Title(title),
+            Body(body) {}
+
+        til::property<winrt::hstring> Title;
+        til::property<winrt::hstring> Body;
+    };
+
     struct WindowSizeChangedEventArgs : public WindowSizeChangedEventArgsT<WindowSizeChangedEventArgs>
     {
     public:

src/cascadia/TerminalControl/EventArgs.idl

@@ -160,6 +160,12 @@ namespace Microsoft.Terminal.Control
         Int32 BufferRow { get; };
     }
 
+    runtimeclass ShowNotificationEventArgs
+    {
+        String Title { get; };
+        String Body { get; };
+    }
+
     runtimeclass WindowSizeChangedEventArgs
     {
         Int32 Width;

src/cascadia/TerminalControl/TermControl.cpp

@@ -328,6 +328,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         _revokers.CompletionsChanged = _core.CompletionsChanged(winrt::auto_revoke, { get_weak(), &TermControl::_bubbleCompletionsChanged });
         _revokers.RestartTerminalRequested = _core.RestartTerminalRequested(winrt::auto_revoke, { get_weak(), &TermControl::_bubbleRestartTerminalRequested });
         _revokers.SearchMissingCommand = _core.SearchMissingCommand(winrt::auto_revoke, { get_weak(), &TermControl::_bubbleSearchMissingCommand });
+        _revokers.ShowNotification = _core.ShowNotification(winrt::auto_revoke, { get_weak(), &TermControl::_bubbleShowNotification });
         _revokers.WindowSizeChanged = _core.WindowSizeChanged(winrt::auto_revoke, { get_weak(), &TermControl::_bubbleWindowSizeChanged });
         _revokers.WriteToClipboard = _core.WriteToClipboard(winrt::auto_revoke, { get_weak(), &TermControl::_bubbleWriteToClipboard });
 

src/cascadia/TerminalControl/TermControl.h

@@ -230,6 +230,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         BUBBLED_FORWARDED_TYPED_EVENT(RestartTerminalRequested, IInspectable, IInspectable);
         BUBBLED_FORWARDED_TYPED_EVENT(WriteToClipboard,         IInspectable, Control::WriteToClipboardEventArgs);
         BUBBLED_FORWARDED_TYPED_EVENT(PasteFromClipboard,       IInspectable, Control::PasteFromClipboardEventArgs);
+        BUBBLED_FORWARDED_TYPED_EVENT(ShowNotification,         IInspectable, Control::ShowNotificationEventArgs);
 
         // clang-format on
 
@@ -468,6 +469,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
             Control::ControlCore::CompletionsChanged_revoker CompletionsChanged;
             Control::ControlCore::RestartTerminalRequested_revoker RestartTerminalRequested;
             Control::ControlCore::SearchMissingCommand_revoker SearchMissingCommand;
+            Control::ControlCore::ShowNotification_revoker ShowNotification;
             Control::ControlCore::RefreshQuickFixUI_revoker RefreshQuickFixUI;
             Control::ControlCore::WindowSizeChanged_revoker WindowSizeChanged;
 

src/cascadia/TerminalControl/TermControl.idl

@@ -82,6 +82,7 @@ namespace Microsoft.Terminal.Control
         event Windows.Foundation.TypedEventHandler<Object, CharSentEventArgs> CharSent;
         event Windows.Foundation.TypedEventHandler<Object, StringSentEventArgs> StringSent;
         event Windows.Foundation.TypedEventHandler<Object, SearchMissingCommandEventArgs> SearchMissingCommand;
+        event Windows.Foundation.TypedEventHandler<Object, ShowNotificationEventArgs> ShowNotification;
 
 
         Microsoft.UI.Xaml.Controls.CommandBarFlyout ContextMenu { get; };

src/cascadia/TerminalCore/ICoreSettings.idl

@@ -124,6 +124,7 @@ namespace Microsoft.Terminal.Core
         Boolean AllowKittyKeyboardMode { get; };
         Boolean AllowVtChecksumReport { get; };
         Boolean AllowVtClipboardWrite { get; };
+        Boolean AllowOscNotifications { get; };
         Boolean TrimBlockSelection { get; };
         Boolean DetectURLs { get; };
 

src/cascadia/TerminalCore/Terminal.cpp

@@ -267,6 +267,7 @@ void Terminal::SetOptionalFeatures(winrt::Microsoft::Terminal::Core::ICoreSettin
     auto features = til::enumset<ITermDispatch::OptionalFeature>{};
     features.set(ITermDispatch::OptionalFeature::ChecksumReport, settings.AllowVtChecksumReport());
     features.set(ITermDispatch::OptionalFeature::ClipboardWrite, settings.AllowVtClipboardWrite());
+    features.set(ITermDispatch::OptionalFeature::DesktopNotification, settings.AllowOscNotifications());
     engine.Dispatch().SetOptionalFeatures(features);
 }
 
@@ -1276,6 +1277,11 @@ void Microsoft::Terminal::Core::Terminal::SetSearchMissingCommandCallback(std::f
     _pfnSearchMissingCommand.swap(pfn);
 }
 
+void Microsoft::Terminal::Core::Terminal::SetShowNotificationCallback(std::function<void(std::wstring_view, std::wstring_view)> pfn) noexcept
+{
+    _pfnShowNotification.swap(pfn);
+}
+
 void Microsoft::Terminal::Core::Terminal::SetClearQuickFixCallback(std::function<void()> pfn) noexcept
 {
     _pfnClearQuickFix.swap(pfn);

src/cascadia/TerminalCore/Terminal.hpp

@@ -165,6 +165,8 @@ public:
 
     void SearchMissingCommand(const std::wstring_view command) override;
 
+    void ShowNotification(const std::wstring_view title, const std::wstring_view body) override;
+
 #pragma endregion
 
     void ClearMark();
@@ -233,6 +235,7 @@ public:
     void SetPlayMidiNoteCallback(std::function<void(const int, const int, const std::chrono::microseconds)> pfn) noexcept;
     void CompletionsChangedCallback(std::function<void(std::wstring_view, unsigned int)> pfn) noexcept;
     void SetSearchMissingCommandCallback(std::function<void(std::wstring_view, const til::CoordType)> pfn) noexcept;
+    void SetShowNotificationCallback(std::function<void(std::wstring_view, std::wstring_view)> pfn) noexcept;
     void SetClearQuickFixCallback(std::function<void()> pfn) noexcept;
     void SetWindowSizeChangedCallback(std::function<void(int32_t, int32_t)> pfn) noexcept;
     void SetSearchHighlights(const std::vector<til::point_span>& highlights) noexcept;
@@ -341,6 +344,7 @@ private:
     std::function<void(const int, const int, const std::chrono::microseconds)> _pfnPlayMidiNote;
     std::function<void(std::wstring_view, unsigned int)> _pfnCompletionsChanged;
     std::function<void(std::wstring_view, const til::CoordType)> _pfnSearchMissingCommand;
+    std::function<void(std::wstring_view, std::wstring_view)> _pfnShowNotification;
     std::function<void()> _pfnClearQuickFix;
     std::function<void(int32_t, int32_t)> _pfnWindowSizeChanged;
 

src/cascadia/TerminalCore/TerminalApi.cpp

@@ -380,6 +380,14 @@ void Terminal::SearchMissingCommand(const std::wstring_view command)
     }
 }
 
+void Terminal::ShowNotification(const std::wstring_view title, const std::wstring_view body)
+{
+    if (_pfnShowNotification)
+    {
+        _pfnShowNotification(title, body);
+    }
+}
+
 void Terminal::NotifyBufferRotation(const int delta)
 {
     // Update our selection, so it doesn't move as the buffer is cycled

src/cascadia/TerminalSettingsAppAdapterLib/TerminalSettings.cpp

@@ -352,6 +352,7 @@ namespace winrt::Microsoft::Terminal::Settings
         _AllowKittyKeyboardMode = profile.AllowKittyKeyboardMode();
         _AllowVtChecksumReport = profile.AllowVtChecksumReport();
         _AllowVtClipboardWrite = profile.AllowVtClipboardWrite();
+        _AllowOscNotifications = profile.AllowOscNotifications();
         _PathTranslationStyle = profile.PathTranslationStyle();
         _DragDropDelimiter = profile.DragDropDelimiter();
     }

src/cascadia/TerminalSettingsEditor/ProfileViewModel.h

@@ -143,6 +143,7 @@ namespace winrt::Microsoft::Terminal::Settings::Editor::implementation
         OBSERVABLE_PROJECTED_SETTING(_profile, AllowKittyKeyboardMode);
         OBSERVABLE_PROJECTED_SETTING(_profile, AllowVtChecksumReport);
         OBSERVABLE_PROJECTED_SETTING(_profile, AllowVtClipboardWrite);
+        OBSERVABLE_PROJECTED_SETTING(_profile, AllowOscNotifications);
         OBSERVABLE_PROJECTED_SETTING(_profile, AnswerbackMessage);
         OBSERVABLE_PROJECTED_SETTING(_profile, RainbowSuggestions);
         OBSERVABLE_PROJECTED_SETTING(_profile, PathTranslationStyle);

src/cascadia/TerminalSettingsEditor/ProfileViewModel.idl

@@ -142,5 +142,6 @@ namespace Microsoft.Terminal.Settings.Editor
         OBSERVABLE_PROJECTED_PROFILE_SETTING(Microsoft.Terminal.Control.PathTranslationStyle, PathTranslationStyle);
         OBSERVABLE_PROJECTED_PROFILE_SETTING(String, DragDropDelimiter);
         OBSERVABLE_PROJECTED_PROFILE_SETTING(Boolean, AllowVtClipboardWrite);
+        OBSERVABLE_PROJECTED_PROFILE_SETTING(Boolean, AllowOscNotifications);
     }
 }

src/cascadia/TerminalSettingsEditor/Profiles_Terminal.xaml

@@ -81,6 +81,16 @@
                               Style="{StaticResource ToggleSwitchInExpanderStyle}" />
             </local:SettingContainer>
 
+            <!--  Allow OSC 777 Desktop Notifications  -->
+            <local:SettingContainer x:Name="AllowOscNotifications"
+                                    x:Uid="Profile_AllowOscNotifications"
+                                    ClearSettingValue="{x:Bind Profile.ClearAllowOscNotifications}"
+                                    HasSettingValue="{x:Bind Profile.HasAllowOscNotifications, Mode=OneWay}"
+                                    SettingOverrideSource="{x:Bind Profile.AllowOscNotificationsOverrideSource, Mode=OneWay}">
+                <ToggleSwitch IsOn="{x:Bind Profile.AllowOscNotifications, Mode=TwoWay}"
+                              Style="{StaticResource ToggleSwitchInExpanderStyle}" />
+            </local:SettingContainer>
+
             <!--  Answerback Message  -->
             <local:SettingContainer x:Name="AnswerbackMessage"
                                     x:Uid="Profile_AnswerbackMessage"

src/cascadia/TerminalSettingsEditor/Resources/en-US/Resources.resw

@@ -573,6 +573,14 @@
     <value>Allow OSC 52 (Manipulate Selection Data) to write to the clipboard</value>
     <comment>{Locked="OSC 52"}{Locked="Manipulate Selection Data"}Header for a control to toggle support for applications to change the contents of the Windows system clipboard.</comment>
   </data>
+  <data name="Profile_AllowOscNotifications.Header" xml:space="preserve">
+    <value>Allow OSC 777 (Desktop Notification) to show toast notifications</value>
+    <comment>{Locked="OSC 777"}{Locked="Desktop Notification"}Header for a control to toggle support for applications to display desktop toast notifications via the OSC 777 escape sequence.</comment>
+  </data>
+  <data name="Profile_AllowOscNotifications.HelpText" xml:space="preserve">
+    <value>When enabled, applications can send the OSC 777 escape sequence to trigger a desktop notification with a custom title and body.</value>
+    <comment>{Locked="OSC 777"}Help text for the OSC 777 desktop notification toggle.</comment>
+  </data>
   <data name="Globals_AllowHeadless.Header" xml:space="preserve">
     <value>Allow Windows Terminal to run in the background</value>
     <comment>Header for a control to toggle support for Windows Terminal to run in the background.</comment>

src/cascadia/TerminalSettingsModel/MTSMSettings.h

@@ -108,6 +108,7 @@ Author(s):
     X(bool, AllowKittyKeyboardMode, "compatibility.kittyKeyboardMode", true)                                                                                   \
     X(bool, AllowVtChecksumReport, "compatibility.allowDECRQCRA", false)                                                                                       \
     X(bool, AllowVtClipboardWrite, "compatibility.allowOSC52", true)                                                                                           \
+    X(bool, AllowOscNotifications, "compatibility.allowOSC777", false)                                                                                         \
     X(bool, AllowKeypadMode, "compatibility.allowDECNKM", false)                                                                                               \
     X(hstring, DragDropDelimiter, "dragDropDelimiter", L" ")                                                                                                   \
     X(Microsoft::Terminal::Control::PathTranslationStyle, PathTranslationStyle, "pathTranslationStyle", Microsoft::Terminal::Control::PathTranslationStyle::None)

src/cascadia/TerminalSettingsModel/Profile.idl

@@ -93,6 +93,7 @@ namespace Microsoft.Terminal.Settings.Model
         INHERITABLE_PROFILE_SETTING(Boolean, AllowVtChecksumReport);
         INHERITABLE_PROFILE_SETTING(Boolean, AllowKeypadMode);
         INHERITABLE_PROFILE_SETTING(Boolean, AllowVtClipboardWrite);
+        INHERITABLE_PROFILE_SETTING(Boolean, AllowOscNotifications);
 
         INHERITABLE_PROFILE_SETTING(Microsoft.Terminal.Control.PathTranslationStyle, PathTranslationStyle);
         INHERITABLE_PROFILE_SETTING(String, DragDropDelimiter);

src/cascadia/inc/ControlProperties.h

@@ -56,7 +56,8 @@
     X(bool, RepositionCursorWithMouse, false)                                                                     \
     X(bool, RainbowSuggestions)                                                                                   \
     X(bool, AllowVtChecksumReport)                                                                                \
-    X(bool, AllowVtClipboardWrite, true)
+    X(bool, AllowVtClipboardWrite, true)                                                                          \
+    X(bool, AllowOscNotifications, false)
 
 // --------------------------- Control Settings ---------------------------
 //  All of these settings are defined in IControlSettings.

src/host/outputStream.cpp

@@ -459,3 +459,7 @@ void ConhostInternalGetSet::SearchMissingCommand(std::wstring_view /*missingComm
 {
     // Not implemented for conhost.
 }
+void ConhostInternalGetSet::ShowNotification(std::wstring_view /*title*/, std::wstring_view /*body*/)
+{
+    // Not implemented for conhost.
+}

src/host/outputStream.hpp

@@ -74,6 +74,8 @@ public:
 
     void SearchMissingCommand(std::wstring_view missingCommand) override;
 
+    void ShowNotification(std::wstring_view title, std::wstring_view body) override;
+
 private:
     Microsoft::Console::IIoProvider& _io;
 };

src/inc/til/string.h

@@ -336,6 +336,18 @@ namespace til // Terminal Implementation Library. Also: "Today I Learned"
             return sentinel{};
         }
 
+        typename iterator::value_type next() noexcept
+        {
+            const auto part = value();
+            advance();
+            return part;
+        }
+
+        typename iterator::value_type remaining() noexcept
+        {
+            return { _it, _end };
+        }
+
     private:
         bool valid() const noexcept
         {

src/terminal/adapter/ITermDispatch.hpp

@@ -29,6 +29,7 @@ public:
     {
         ChecksumReport,
         ClipboardWrite,
+        DesktopNotification,
     };
 
 #pragma warning(push)
@@ -162,6 +163,8 @@ public:
     virtual void DoVsCodeAction(const std::wstring_view string) = 0;
     virtual void DoWTAction(const std::wstring_view string) = 0;
 
+    virtual void DoUrxvtAction(const std::wstring_view string) = 0;
+
     virtual StringHandler DefineSixelImage(const VTInt macroParameter,
                                            const DispatchTypes::SixelBackground backgroundSelect,
                                            const VTParameter backgroundColor) = 0; // SIXEL

src/terminal/adapter/ITerminalApi.hpp

@@ -92,5 +92,7 @@ namespace Microsoft::Console::VirtualTerminal
         virtual void InvokeCompletions(std::wstring_view menuJson, unsigned int replaceLength) = 0;
 
         virtual void SearchMissingCommand(const std::wstring_view command) = 0;
+
+        virtual void ShowNotification(const std::wstring_view title, const std::wstring_view body) = 0;
     };
 }

src/terminal/adapter/adaptDispatch.cpp

@@ -3872,6 +3872,41 @@ void AdaptDispatch::DoWTAction(const std::wstring_view string)
     }
 }
 
+// Method Description:
+// - OSC 777 - Handles urxvt requests. Currently, the only supported request is for desktop notifications.
+//   The format is: OSC 777;notify;title;body ST
+// Arguments:
+// - string: contains the parameters that define the notification
+void AdaptDispatch::DoUrxvtAction(const std::wstring_view string)
+{
+    if (!_optionalFeatures.test(OptionalFeature::DesktopNotification))
+    {
+        return;
+    }
+
+    const auto parts = Utils::SplitString(string, L';');
+
+    if (parts.size() < 1)
+    {
+        return;
+    }
+
+    til::split_iterator split{ string, L';' };
+    const auto action = split.next();
+    if (action == L"notify")
+    {
+        // The body is everything after "notify;title;". We can't just use
+        // parts[2] because the body itself may contain semicolons.
+        const auto title = split.next();
+        const auto body = split.remaining();
+        _api.ShowNotification(title, body);
+    }
+    else
+    {
+        _api.UnknownSequence();
+    }
+}
+
 // Method Description:
 // - SIXEL - Defines an image transmitted in sixel format via the returned
 //   StringHandler function.

src/terminal/adapter/adaptDispatch.hpp

@@ -163,6 +163,8 @@ namespace Microsoft::Console::VirtualTerminal
 
         void DoWTAction(const std::wstring_view string) override;
 
+        void DoUrxvtAction(const std::wstring_view string) override;
+
         StringHandler DefineSixelImage(const VTInt macroParameter,
                                        const DispatchTypes::SixelBackground backgroundSelect,
                                        const VTParameter backgroundColor) override; // SIXEL

src/terminal/adapter/termDispatch.hpp

@@ -153,6 +153,8 @@ public:
 
     void DoWTAction(const std::wstring_view /*string*/) override {}
 
+    void DoUrxvtAction(const std::wstring_view /*string*/) override {}
+
     StringHandler DefineSixelImage(const VTInt /*macroParameter*/,
                                    const DispatchTypes::SixelBackground /*backgroundSelect*/,
                                    const VTParameter /*backgroundColor*/) override { return nullptr; }; // SIXEL

src/terminal/adapter/ut_adapter/adapterTest.cpp

@@ -233,6 +233,11 @@ public:
         Log::Comment(L"SearchMissingCommand MOCK called...");
     }
 
+    void ShowNotification(const std::wstring_view /*title*/, const std::wstring_view /*body*/) override
+    {
+        Log::Comment(L"ShowNotification MOCK called...");
+    }
+
     void PrepData()
     {
         PrepData(CursorDirection::UP); // if called like this, the cursor direction doesn't matter.

src/terminal/parser/OutputStateMachineEngine.cpp

@@ -909,6 +909,9 @@ bool OutputStateMachineEngine::ActionOscDispatch(const size_t parameter, const s
         _dispatch->DoWTAction(string);
         break;
     }
+    case OscActionCodes::UrxvtAction:
+        _dispatch->DoUrxvtAction(string);
+        break;
     default:
         _dispatch->UnknownSequence();
         break;

src/terminal/parser/OutputStateMachineEngine.hpp

@@ -227,6 +227,7 @@ namespace Microsoft::Console::VirtualTerminal
             ResetHighlightColor = 117,
             FinalTermAction = 133,
             VsCodeAction = 633,
+            UrxvtAction = 777,
             ITerm2Action = 1337,
             WTAction = 9001,
         };