From c4cc796f8697780db756af2811dd0f3c09bd38b3 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Tue, 4 Jan 2022 17:32:19 +0100
Subject: [PATCH] LibGUI: Make GUI::UndoStack remember time it was last set to
 unmodified

This can be used to determine how much time has passed since a document
was saved. :^)
---
 Userland/Libraries/LibGUI/UndoStack.cpp | 1 +
 Userland/Libraries/LibGUI/UndoStack.h   | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/Userland/Libraries/LibGUI/UndoStack.cpp b/Userland/Libraries/LibGUI/UndoStack.cpp
index 9ca07e0f57..6c265672c4 100644
--- a/Userland/Libraries/LibGUI/UndoStack.cpp
+++ b/Userland/Libraries/LibGUI/UndoStack.cpp
@@ -80,6 +80,7 @@ void UndoStack::set_current_unmodified()
         return;
 
     m_clean_index = m_stack_index;
+    m_last_unmodified_timestamp = Time::now_monotonic();
 
     if (on_state_change)
         on_state_change();
diff --git a/Userland/Libraries/LibGUI/UndoStack.h b/Userland/Libraries/LibGUI/UndoStack.h
index 44dd9ca0bf..cfc0b2c6ca 100644
--- a/Userland/Libraries/LibGUI/UndoStack.h
+++ b/Userland/Libraries/LibGUI/UndoStack.h
@@ -8,6 +8,7 @@
 
 #include <AK/Function.h>
 #include <AK/NonnullOwnPtrVector.h>
+#include <AK/Time.h>
 #include <LibGUI/Forward.h>
 
 namespace GUI {
@@ -28,6 +29,8 @@ public:
     void set_current_unmodified();
     bool is_current_modified() const;
 
+    Optional<Time> last_unmodified_timestamp() const { return m_last_unmodified_timestamp; }
+
     void clear();
 
     Optional<String> undo_action_text() const;
@@ -39,6 +42,7 @@ private:
     NonnullOwnPtrVector<Command> m_stack;
     size_t m_stack_index { 0 };
     Optional<size_t> m_clean_index;
+    Optional<Time> m_last_unmodified_timestamp;
 };
 
 }