Persist window layout every few minutes (#18898)

If `persistedWindowLayout` is enabled, we now persist the window layout
every few minutes (excluding the text buffer).

This was done by adding a `SafeDispatcherTimer` to the `WindowEmperor`
that calls `PersistState()` every 5 minutes. For `BuildStartupKind`, I
split up `Persist` into `PersistAll` and `PersistLayout`. This way, we
go through all the same code flow that `Persist` had except for
specifically serializing the buffer.

## Validation Steps Performed
✅ (with the timer set to 3 seconds) create a window layout and ensure
the layout is restored after forcefully stopping Terminal (aka
simulating a "crash")

Closes #18838

src/cascadia/TerminalApp/IPaneContent.idl

@@ -8,7 +8,8 @@ namespace TerminalApp
         None,
         Content,
         MovePane,
-        Persist,
+        PersistLayout,
+        PersistAll
     };
 
     runtimeclass BellEventArgs

src/cascadia/TerminalApp/TerminalPage.cpp

@@ -1953,7 +1953,7 @@ namespace winrt::TerminalApp::implementation
         }
     }
 
-    void TerminalPage::PersistState()
+    void TerminalPage::PersistState(bool serializeBuffer)
     {
         // This method may be called for a window even if it hasn't had a tab yet or lost all of them.
         // We shouldn't persist such windows.
@@ -1968,7 +1968,7 @@ namespace winrt::TerminalApp::implementation
         for (auto tab : _tabs)
         {
             auto t = winrt::get_self<implementation::TabBase>(tab);
-            auto tabActions = t->BuildStartupActions(BuildStartupKind::Persist);
+            auto tabActions = t->BuildStartupActions(serializeBuffer ? BuildStartupKind::PersistAll : BuildStartupKind::PersistLayout);
             actions.insert(actions.end(), std::make_move_iterator(tabActions.begin()), std::make_move_iterator(tabActions.end()));
         }
 

src/cascadia/TerminalApp/TerminalPage.h

@@ -113,7 +113,7 @@ namespace winrt::TerminalApp::implementation
 
         safe_void_coroutine RequestQuit();
         safe_void_coroutine CloseWindow();
-        void PersistState();
+        void PersistState(bool serializeBuffer);
 
         void ToggleFocusMode();
         void ToggleFullscreen();

src/cascadia/TerminalApp/TerminalPaneContent.cpp

@@ -141,7 +141,7 @@ namespace winrt::TerminalApp::implementation
             // "attach existing" rather than a "create"
             args.ContentId(_control.ContentId());
             break;
-        case BuildStartupKind::Persist:
+        case BuildStartupKind::PersistAll:
         {
             const auto connection = _control.Connection();
             const auto id = connection ? connection.SessionId() : winrt::guid{};
@@ -156,6 +156,7 @@ namespace winrt::TerminalApp::implementation
             }
             break;
         }
+        case BuildStartupKind::PersistLayout:
         default:
             break;
         }

src/cascadia/TerminalApp/TerminalWindow.cpp

@@ -266,11 +266,11 @@ namespace winrt::TerminalApp::implementation
         AppLogic::Current()->NotifyRootInitialized();
     }
 
-    void TerminalWindow::PersistState()
+    void TerminalWindow::PersistState(bool serializeBuffer)
     {
         if (_root)
         {
-            _root->PersistState();
+            _root->PersistState(serializeBuffer);
         }
     }
 

src/cascadia/TerminalApp/TerminalWindow.h

@@ -71,7 +71,7 @@ namespace winrt::TerminalApp::implementation
 
         void Create();
 
-        void PersistState();
+        void PersistState(bool serializeBuffer);
 
         void UpdateSettings(winrt::TerminalApp::SettingsLoadEventArgs args);
 

src/cascadia/TerminalApp/TerminalWindow.idl

@@ -59,7 +59,7 @@ namespace TerminalApp
         Boolean ShouldImmediatelyHandoffToElevated();
         void HandoffToElevated();
 
-        void PersistState();
+        void PersistState(Boolean serializeBuffer);
 
         Windows.UI.Xaml.UIElement GetRoot();
 

src/cascadia/WindowsTerminal/WindowEmperor.cpp

@@ -314,6 +314,7 @@ void WindowEmperor::HandleCommandlineArgs(int nCmdShow)
     _createMessageWindow(windowClassName.c_str());
     _setupGlobalHotkeys();
     _checkWindowsForNotificationIcon();
+    _setupSessionPersistence(_app.Logic().Settings().GlobalSettings().ShouldUsePersistedLayout());
 
     // When the settings change, we'll want to update our global hotkeys
     // and our notification icon based on the new settings.
@@ -323,6 +324,7 @@ void WindowEmperor::HandleCommandlineArgs(int nCmdShow)
             _assertIsMainThread();
             _setupGlobalHotkeys();
             _checkWindowsForNotificationIcon();
+            _setupSessionPersistence(args.NewSettings().GlobalSettings().ShouldUsePersistedLayout());
         }
     });
 
@@ -921,10 +923,22 @@ LRESULT WindowEmperor::_messageHandler(HWND window, UINT const message, WPARAM c
     return DefWindowProcW(window, message, wParam, lParam);
 }
 
-void WindowEmperor::_finalizeSessionPersistence() const
+void WindowEmperor::_setupSessionPersistence(bool enabled)
 {
-    const auto state = ApplicationState::SharedInstance();
+    if (!enabled)
+    {
+        _persistStateTimer.Stop();
+        return;
+    }
+    _persistStateTimer.Interval(std::chrono::minutes(5));
+    _persistStateTimer.Tick([&](auto&&, auto&&) {
+        _persistState(ApplicationState::SharedInstance(), false);
+    });
+    _persistStateTimer.Start();
+}
 
+void WindowEmperor::_persistState(const ApplicationState& state, bool serializeBuffer) const
+{
     // Calling an `ApplicationState` setter triggers a write to state.json.
     // With this if condition we avoid an unnecessary write when persistence is disabled.
     if (state.PersistedWindowLayouts())
@@ -936,12 +950,19 @@ void WindowEmperor::_finalizeSessionPersistence() const
     {
         for (const auto& w : _windows)
         {
-            w->Logic().PersistState();
+            w->Logic().PersistState(serializeBuffer);
         }
     }
 
-    // Ensure to write the state.json before we TerminateProcess()
+    // Ensure to write the state.json
     state.Flush();
+}
+
+void WindowEmperor::_finalizeSessionPersistence() const
+{
+    const auto state = ApplicationState::SharedInstance();
+
+    _persistState(state, true);
 
     if (_needsPersistenceCleanup)
     {

src/cascadia/WindowsTerminal/WindowEmperor.h

@@ -64,6 +64,8 @@ private:
     void _registerHotKey(int index, const winrt::Microsoft::Terminal::Control::KeyChord& hotkey) noexcept;
     void _unregisterHotKey(int index) noexcept;
     void _setupGlobalHotkeys();
+    void _setupSessionPersistence(bool enabled);
+    void _persistState(const winrt::Microsoft::Terminal::Settings::Model::ApplicationState& state, bool serializeBuffer) const;
     void _finalizeSessionPersistence() const;
     void _checkWindowsForNotificationIcon();
 
@@ -77,6 +79,7 @@ private:
     bool _notificationIconShown = false;
     bool _forcePersistence = false;
     bool _needsPersistenceCleanup = false;
+    SafeDispatcherTimer _persistStateTimer;
     std::optional<bool> _currentSystemThemeIsDark;
     int32_t _windowCount = 0;
     int32_t _messageBoxCount = 0;