destroy all textures on window destruction and restore OpenGL objects when Android resumes the app

engine/layout.cpp

@@ -534,6 +534,9 @@ void Node::clone_children(Node* dest) const
 
 bool LayoutManager::load(const char* path)
 {
+    if (m_loaded)
+        return true; // already loaded
+
 #ifndef __ANDROID__
     struct stat tmp_info;
     if (stat(path, &tmp_info) != 0)
@@ -598,6 +601,7 @@ bool LayoutManager::load(const char* path)
     }
     if (on_loaded)
         on_loaded();
+    m_loaded = true;
 
     return true;
 }