new_editor: make window sync rollback safe

new_editor/app/Platform/Win32/WindowManager/WindowSync.cpp

@@ -10,6 +10,16 @@
 
 namespace XCEngine::UI::Editor::App::Internal {
 
+namespace {
+
+struct ExistingWindowSnapshot {
+    EditorWindow* window = nullptr;
+    UIEditorWorkspaceController workspaceController = {};
+    std::wstring title = {};
+};
+
+} // namespace
+
 std::wstring EditorWindowWorkspaceCoordinator::BuildWindowTitle(
     const UIEditorWorkspaceController& workspaceController) const {
     const std::string& activePanelId = workspaceController.GetWorkspace().activePanelId;
@@ -54,13 +64,62 @@ bool EditorWindowWorkspaceCoordinator::SynchronizeWindowsFromWindowSet(
     const UIEditorWindowWorkspaceSet& windowSet,
     std::string_view preferredNewWindowId,
     const POINT& preferredScreenPoint) {
+    const auto restoreWindowSnapshot = [](const ExistingWindowSnapshot& snapshot) {
+        if (snapshot.window == nullptr) {
+            return;
+        }
+
+        snapshot.window->ReplaceWorkspaceController(snapshot.workspaceController);
+        snapshot.window->SetTitle(snapshot.title);
+        snapshot.window->ResetInteractionState();
+        if (snapshot.window->GetHwnd() != nullptr) {
+            SetWindowTextW(snapshot.window->GetHwnd(), snapshot.window->GetTitle().c_str());
+        }
+    };
+
+    const auto destroyAndEraseWindowById = [this](std::string_view windowId) {
+        auto& windows = m_hostRuntime.GetWindows();
+        const auto it = std::find_if(
+            windows.begin(),
+            windows.end(),
+            [windowId](const std::unique_ptr<EditorWindow>& candidate) {
+                return candidate != nullptr && candidate->GetWindowId() == windowId;
+            });
+        if (it == windows.end() || *it == nullptr) {
+            return false;
+        }
+
+        EditorWindow& window = *it->get();
+        const HWND hwnd = window.GetHwnd();
+        if (GetCapture() == hwnd) {
+            ReleaseCapture();
+        }
+
+        window.Shutdown();
+        if (hwnd != nullptr && IsWindow(hwnd)) {
+            DestroyWindow(hwnd);
+        }
+        window.MarkDestroyed();
+        windows.erase(it);
+        return true;
+    };
+
     std::vector<std::string> windowIdsInSet = {};
     windowIdsInSet.reserve(windowSet.windows.size());
+    std::vector<ExistingWindowSnapshot> existingWindowSnapshots = {};
+    existingWindowSnapshots.reserve(windowSet.windows.size());
+    std::vector<std::string> createdWindowIds = {};
 
     for (const UIEditorWindowWorkspaceState& entry : windowSet.windows) {
         windowIdsInSet.push_back(entry.windowId);
         if (EditorWindow* existingWindow = m_hostRuntime.FindWindow(entry.windowId);
             existingWindow != nullptr) {
+            existingWindow->ClearClosing();
+            existingWindowSnapshots.push_back(ExistingWindowSnapshot{
+                existingWindow,
+                existingWindow->GetWorkspaceController(),
+                existingWindow->GetTitle(),
+            });
             existingWindow->ReplaceWorkspaceController(BuildWorkspaceControllerForWindow(entry));
             existingWindow->ResetInteractionState();
             if (!existingWindow->IsPrimary()) {
@@ -93,8 +152,15 @@ bool EditorWindowWorkspaceCoordinator::SynchronizeWindowsFromWindowSet(
         }
 
         if (m_hostRuntime.CreateEditorWindow(BuildWorkspaceControllerForWindow(entry), createParams) == nullptr) {
+            for (const ExistingWindowSnapshot& snapshot : existingWindowSnapshots) {
+                restoreWindowSnapshot(snapshot);
+            }
+            for (auto it = createdWindowIds.rbegin(); it != createdWindowIds.rend(); ++it) {
+                destroyAndEraseWindowById(*it);
+            }
             return false;
         }
+        createdWindowIds.push_back(entry.windowId);
     }
 
     for (const std::unique_ptr<EditorWindow>& window : m_hostRuntime.GetWindows()) {
@@ -110,6 +176,7 @@ bool EditorWindowWorkspaceCoordinator::SynchronizeWindowsFromWindowSet(
                 windowIdsInSet.end(),
                 window->GetWindowId()) != windowIdsInSet.end();
         if (!existsInWindowSet) {
+            window->MarkClosing();
             PostMessageW(window->GetHwnd(), WM_CLOSE, 0, 0);
         }
     }