Don't create background queries for Results on threads without runloops

src/binding_context.hpp

@@ -70,6 +70,10 @@ class BindingContext {
 public:
     virtual ~BindingContext() = default;
 
+    // If the user adds a notification handler to the Realm, will it ever
+    // actually be called?
+    virtual bool can_deliver_notifications() const noexcept { return true; }
+
     // Called by the Realm when a write transaction is committed to the file by
     // a different Realm instance (possibly in a different process)
     virtual void changes_available() { }

src/results.cpp

@@ -180,7 +180,7 @@ void Results::update_tableview()
             if (!m_live) {
                 return;
             }
-            if (!m_realm->config().read_only && !m_realm->is_in_transaction() && !m_background_query) {
+            if (!m_background_query && !m_realm->is_in_transaction() && m_realm->can_deliver_notifications()) {
                 m_background_query = std::make_shared<_impl::AsyncQuery>(*this);
                 _impl::RealmCoordinator::register_query(m_background_query);
             }

src/shared_realm.cpp

@@ -411,6 +411,19 @@ bool Realm::refresh()
     return true;
 }
 
+bool Realm::can_deliver_notifications() const noexcept
+{
+    if (m_config.read_only) {
+        return false;
+    }
+
+    if (m_binding_context && !m_binding_context->can_deliver_notifications()) {
+        return false;
+    }
+
+    return true;
+}
+
 uint64_t Realm::get_schema_version(const realm::Realm::Config &config)
 {
     auto coordinator = RealmCoordinator::get_existing_coordinator(config.path);

src/shared_realm.hpp

@@ -107,6 +107,8 @@ namespace realm {
         void verify_thread() const;
         void verify_in_write() const;
 
+        bool can_deliver_notifications() const noexcept;
+
         // Close this Realm and remove it from the cache. Continuing to use a
         // Realm after closing it will produce undefined behavior.
         void close();