Add a system message to session restore (#17113)

This adds a system message which displays the time at which the
buffer snapshot was written to disk.

Additionally, this PR moves the snapshot loading into a background
thread, so that the UI thread is unblocked and that multiple
tabs/panes can load simultaneously.

Closes #17031
Closes #17074

## Validation Steps Performed
Repeatedly closing and opening WT adds more and more messages.
Currently, the messages get somewhat corrupted due to a bug
in our line-wrap handling, or some similar part.

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

@@ -1718,6 +1718,7 @@ sysparams
 sysparamsext
 SYSTEMHAND
 SYSTEMMENU
+SYSTEMTIME
 tabview
 TAdd
 taef

src/cascadia/TerminalControl/ControlCore.cpp

@@ -1777,6 +1777,38 @@ namespace winrt::Microsoft::Terminal::Control::implementation
  return;
  }
 
+ FILETIME lastWriteTime;
+ SYSTEMTIME lastWriteSystemTime;
+ if (!GetFileTime(file.get(), nullptr, nullptr, &lastWriteTime) ||
+ !FileTimeToSystemTime(&lastWriteTime, &lastWriteSystemTime))
+ {
+ return;
+ }
+
+ wchar_t dateBuf[256];
+ const auto dateLen = GetDateFormatEx(nullptr, 0, &lastWriteSystemTime, nullptr, &dateBuf[0], ARRAYSIZE(dateBuf), nullptr);
+ wchar_t timeBuf[256];
+ const auto timeLen = GetTimeFormatEx(nullptr, 0, &lastWriteSystemTime, nullptr, &timeBuf[0], ARRAYSIZE(timeBuf));
+
+ std::wstring message;
+ if (dateLen > 0 && timeLen > 0)
+ {
+ const auto msg = RS_(L"SessionRestoreMessage");
+ const std::wstring_view date{ &dateBuf[0], gsl::narrow_cast<size_t>(dateLen) };
+ const std::wstring_view time{ &timeBuf[0], gsl::narrow_cast<size_t>(timeLen) };
+ // This escape sequence string
+ // * sets the color to white on a bright black background ("\x1b[100;37m")
+ // * prints " [Restored <date> <time>] <spaces until end of line> "
+ // * resets the color ("\x1b[m")
+ // * newlines
+ // * clears the screen ("\x1b[2J")
+ // The last step is necessary because we launch ConPTY without PSEUDOCONSOLE_INHERIT_CURSOR by default.
+ // This will cause ConPTY to emit a \x1b[2J sequence on startup to ensure it and the terminal are in-sync.
+ // If we didn't do a \x1b[2J ourselves as well, the user would briefly see the last state of the terminal,
+ // before it's quickly scrolled away once ConPTY has finished starting up, which looks weird.
+ message = fmt::format(FMT_COMPILE(L"\x1b[100;37m [{} {} {}]\x1b[K\x1b[m\r\n\x1b[2J"), msg, date, time);
+ }
+
  wchar_t buffer[32 * 1024];
  DWORD read = 0;
 
@@ -1802,9 +1834,17 @@ namespace winrt::Microsoft::Terminal::Control::implementation
  }
  }
 
- // This pushes the restored contents up into the scrollback.
- const auto lock = _terminal->LockForWriting();
- _terminal->Write(L"\x1b[2J");
+ {
+ const auto lock = _terminal->LockForWriting();
+
+ // Normally the cursor should already be at the start of the line, but let's be absolutely sure it is.
+ if (_terminal->GetCursorPosition().x != 0)
+ {
+ _terminal->Write(L"\r\n");
+ }
+
+ _terminal->Write(message);
+ }
  }
 
  void ControlCore::_rendererWarning(const HRESULT hr, wil::zwstring_view parameter)

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

@@ -296,4 +296,8 @@ Please either install the missing font or choose another one.</value>
  <value>Select output</value>
  <comment>The tooltip for a button for selecting all of a command's output</comment>
  </data>
+ <data name="SessionRestoreMessage" xml:space="preserve">
+ <value>Restored</value>
+ <comment>"Restored" as in "This content was restored"</comment>
+ </data>
 </root>

src/cascadia/TerminalControl/TermControl.cpp

@@ -1187,11 +1187,12 @@ namespace winrt::Microsoft::Terminal::Control::implementation
 
  if (!_restorePath.empty())
  {
- winrt::get_self<ControlCore>(_core)->RestoreFromPath(_restorePath.c_str());
- _restorePath = {};
+ _restoreInBackground();
+ }
+ else
+ {
+ _core.Connection().Start();
  }
-
- _core.Connection().Start();
  }
  else
  {
@@ -1278,6 +1279,44 @@ namespace winrt::Microsoft::Terminal::Control::implementation
  return true;
  }
 
+ winrt::fire_and_forget TermControl::_restoreInBackground()
+ {
+ const auto path = std::exchange(_restorePath, {});
+ const auto weakSelf = get_weak();
+ winrt::apartment_context uiThread;
+
+ try
+ {
+ co_await winrt::resume_background();
+
+ const auto self = weakSelf.get();
+ if (!self)
+ {
+ co_return;
+ }
+
+ winrt::get_self<ControlCore>(_core)->RestoreFromPath(path.c_str());
+ }
+ CATCH_LOG();
+
+ try
+ {
+ co_await uiThread;
+
+ const auto self = weakSelf.get();
+ if (!self)
+ {
+ co_return;
+ }
+
+ if (const auto connection = _core.Connection())
+ {
+ connection.Start();
+ }
+ }
+ CATCH_LOG();
+ }
+
  void TermControl::_CharacterHandler(const winrt::Windows::Foundation::IInspectable& /*sender*/,
  const Input::CharacterReceivedRoutedEventArgs& e)
  {

src/cascadia/TerminalControl/TermControl.h

@@ -319,6 +319,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
  Reattach
  };
  bool _InitializeTerminal(const InitializeReason reason);
+ winrt::fire_and_forget _restoreInBackground();
  void _SetFontSize(int fontSize);
  void _TappedHandler(const Windows::Foundation::IInspectable& sender, const Windows::UI::Xaml::Input::TappedRoutedEventArgs& e);
  void _KeyDownHandler(const Windows::Foundation::IInspectable& sender, const Windows::UI::Xaml::Input::KeyRoutedEventArgs& e);