Pane officially opened via the serialized actions, via across the process boundary

src/cascadia/TerminalApp/Pane.cpp

@@ -205,7 +205,8 @@ Pane::BuildStartupState Pane::BuildStartupActions(uint32_t currentId, uint32_t n
         // When creating a pane the split size is the size of the new pane
         // and not position.
         const auto splitDirection = _splitState == SplitState::Horizontal ? SplitDirection::Down : SplitDirection::Right;
-        SplitPaneArgs args{ SplitType::Manual, splitDirection, 1. - _desiredSplitPosition, terminalArgs };
+        const auto splitSize = (asContent && _IsLeaf() ? .5 : 1. - _desiredSplitPosition);
+        SplitPaneArgs args{ SplitType::Manual, splitDirection, splitSize, terminalArgs };
         actionAndArgs.Args(args);
 
         return actionAndArgs;

src/cascadia/TerminalApp/TerminalPage.cpp

@@ -1937,6 +1937,15 @@ namespace winrt::TerminalApp::implementation
 
         content;
         tabIndex;
+
+        auto args = ActionAndArgs::Deserialize(content);
+        // TODO! if the first action is a split pane and tabIndex > tabs.size,
+        // then remove it and insert an equivalent newTab
+
+        for (const auto& action : args)
+        {
+            _actionDispatch->DoAction(action);
+        }
         co_await wil::resume_foreground(Dispatcher());
     }
     // Method Description:
@@ -2038,6 +2047,8 @@ namespace winrt::TerminalApp::implementation
                                                                   const float splitSize,
                                                                   PreparedContent preppedContent)
     {
+        // _GetFocusedTabImpl requires us to be on the UI thread
+        co_await wil::resume_foreground(Dispatcher(), CoreDispatcherPriority::Normal);
         auto focusedTab{ _GetFocusedTabImpl() };
 
         // Clever hack for a crash in startup, with multiple sub-commands. Say
@@ -2720,7 +2731,9 @@ namespace winrt::TerminalApp::implementation
     {
         PreparedContent preppedContent;
         _evaluateSettings(newTerminalArgs, duplicate, preppedContent.controlSettings, preppedContent.profile);
-        preppedContent.initContentProc = _CreateNewContentProcess(preppedContent.profile, preppedContent.controlSettings);
+        preppedContent.initContentProc = (newTerminalArgs && newTerminalArgs.ContentGuid() != winrt::guid{}) ?
+                                             _AttachToContentProcess(newTerminalArgs.ContentGuid()) :
+                                             _CreateNewContentProcess(preppedContent.profile, preppedContent.controlSettings);
         return preppedContent;
     }
 
@@ -2765,7 +2778,7 @@ namespace winrt::TerminalApp::implementation
         co_return content;
     }
 
-    ContentProcess TerminalPage::_AttachToContentProcess(const winrt::guid contentGuid)
+    Windows::Foundation::IAsyncOperation<ContentProcess> TerminalPage::_AttachToContentProcess(const winrt::guid contentGuid)
     {
         ContentProcess content{ nullptr };
         try
@@ -2775,7 +2788,7 @@ namespace winrt::TerminalApp::implementation
         catch (winrt::hresult_error hr)
         {
         }
-        return content;
+        co_return content;
     }
 
     // INVARIANT: Must be called on UI thread!

src/cascadia/TerminalApp/TerminalPage.h

@@ -482,7 +482,7 @@ namespace winrt::TerminalApp::implementation
                                             const bool duplicate);
         Windows::Foundation::IAsyncOperation<winrt::Microsoft::Terminal::Control::ContentProcess> _CreateNewContentProcess(winrt::Microsoft::Terminal::Settings::Model::Profile profile,
                                                                                                                            winrt::Microsoft::Terminal::Settings::Model::TerminalSettingsCreateResult settings);
-        winrt::Microsoft::Terminal::Control::ContentProcess _AttachToContentProcess(const winrt::guid contentGuid);
+        Windows::Foundation::IAsyncOperation<winrt::Microsoft::Terminal::Control::ContentProcess> _AttachToContentProcess(const winrt::guid contentGuid);
 
         winrt::fire_and_forget _createNewTabFromContent(PreparedContent preppedContent,
                                                         std::function<void(const winrt::com_ptr<TerminalTab>&)> postInitTab = nullptr);

src/cascadia/TerminalControl/ControlCore.cpp

@@ -1343,6 +1343,9 @@ namespace winrt::Microsoft::Terminal::Control::implementation
     // - duration - How long the note should be sustained (in microseconds).
     void ControlCore::_terminalPlayMidiNote(const int noteNumber, const int velocity, const std::chrono::microseconds duration)
     {
+        // TODO! GH#1256 This is intentionally here to conflict with https://github.com/microsoft/terminal/pull/13471#pullrequestreview-1039353718
+        // When we do tearout, we'll need to also recreate the midi thing
+
         // We create the audio instance on demand, and lock it for the duration
         // of the note output so it can't be destroyed while in use.
         auto& midiAudio = _getMidiAudio();
@@ -1989,6 +1992,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
     {
         if (owner != _owningHwnd && _connection)
         {
+            // TODO GH#1256 change the midi HWND too
             if (auto conpty{ _connection.try_as<TerminalConnection::ConptyConnection>() })
             {
                 conpty.ReparentWindow(owner);

src/cascadia/TerminalSettingsModel/ActionAndArgs.cpp

@@ -426,5 +426,21 @@ namespace winrt::Microsoft::Terminal::Settings::Model::implementation
         auto str = Json::writeString(wbuilder, json);
         return winrt::to_hstring(str);
     }
+    winrt::Windows::Foundation::Collections::IVector<Model::ActionAndArgs> ActionAndArgs::Deserialize(winrt::hstring content)
+    {
+        auto data = winrt::to_string(content);
+
+        std::string errs;
+        std::unique_ptr<Json::CharReader> reader{ Json::CharReaderBuilder::CharReaderBuilder().newCharReader() };
+        Json::Value root;
+        if (!reader->parse(data.data(), data.data() + data.size(), &root, &errs))
+        {
+            throw winrt::hresult_error(WEB_E_INVALID_JSON_STRING, winrt::to_hstring(errs));
+        }
+
+        winrt::Windows::Foundation::Collections::IVector<Model::ActionAndArgs> result{ nullptr };
+        JsonUtils::GetValueForKey(root, "actions", result);
+        return result;
+    }
 
 }

src/cascadia/TerminalSettingsModel/ActionAndArgs.h

@@ -17,6 +17,7 @@ namespace winrt::Microsoft::Terminal::Settings::Model::implementation
         static Json::Value ToJson(const Model::ActionAndArgs& val);
 
         static winrt::hstring Serialize(winrt::Windows::Foundation::Collections::IVector<Model::ActionAndArgs> args);
+        static winrt::Windows::Foundation::Collections::IVector<Model::ActionAndArgs> Deserialize(winrt::hstring content);
 
         ActionAndArgs() = default;
         ActionAndArgs(ShortcutAction action);

src/cascadia/TerminalSettingsModel/Command.idl

@@ -25,6 +25,7 @@ namespace Microsoft.Terminal.Settings.Model
         ActionAndArgs(ShortcutAction action, IActionArgs args);
 
         static String Serialize(IVector<ActionAndArgs> args);
+        static IVector<ActionAndArgs> Deserialize(String content);
 
         IActionArgs Args;
         ShortcutAction Action;