Tables, Menus: Fixed tables or child windows submitted inside BeginMainMenuBar() being unable to save their settings. (#8356)

Amend error handling (fa178f4) to avoid us setting ImGuiWindowFlags_NoSavedSettings on the wrong window.

docs/CHANGELOG.txt

@@ -75,6 +75,8 @@ Other changes:
 - Tables, Menus: Fixed using BeginTable() in menu layer (any menu bar). (#8355)
   It previously overrode the current layer back to main layer, which caused an issue
   with MainMenuBar attempted to release focus when leaving the menu layer.
+- Tables, Menus: Fixed tables or child windows submitted inside BeginMainMenuBar()
+  being unable to save their settings, as the main menu bar uses _NoSavedSettings. (#8356)
 - ColorEdit, ColorPicker: Fixed alpha preview broken in 1.91.7. (#8336, #8241). [@PathogenDavid]
 - Tabs, Style: reworked selected overline rendering to better accommodate
   for rounded tabs. Reduced default thickness (style.TabBarOverlineSize),

imgui_widgets.cpp

@@ -8755,18 +8755,29 @@ bool ImGui::BeginMainMenuBar()
     float height = GetFrameHeight();
     bool is_open = BeginViewportSideBar("##MainMenuBar", viewport, ImGuiDir_Up, height, window_flags);
     g.NextWindowData.MenuBarOffsetMinVal = ImVec2(0.0f, 0.0f);
-
-    if (is_open)
-        BeginMenuBar();
-    else
+    if (!is_open)
+    {
         End();
+        return false;
+    }
+
+    // Temporarily disable _NoSavedSettings, in the off-chance that tables or child windows submitted within the menu-bar may want to use settings. (#8356)
+    g.CurrentWindow->Flags &= ~ImGuiWindowFlags_NoSavedSettings;
+    BeginMenuBar();
     return is_open;
 }
 
 void ImGui::EndMainMenuBar()
 {
     ImGuiContext& g = *GImGui;
+    if (!g.CurrentWindow->DC.MenuBarAppending)
+    {
+        IM_ASSERT_USER_ERROR(0, "Calling EndMainMenuBar() not from a menu-bar!"); // Not technically testing that it is the main menu bar
+        return;
+    }
+
     EndMenuBar();
+    g.CurrentWindow->Flags |= ImGuiWindowFlags_NoSavedSettings; // Restore _NoSavedSettings (#8356)
 
     // When the user has left the menu layer (typically: closed menus through activation of an item), we restore focus to the previous window
     // FIXME: With this strategy we won't be able to restore a NULL focus.