add xml attributes for combobox node and add resolution selection for new doc

engine/app_dialogs.cpp

@@ -30,9 +30,11 @@ void App::dialog_newdoc()
                 if (auto docname = layout[main_id]->find<NodeText>("txt-docname"))
                     docname->set_text(("Panodoc: " + doc_name).c_str());
 
+                int res = atoi(dialog->m_resolution->labels[dialog->m_resolution->m_current_index].c_str());
                 layers->clear();
                 canvas->m_canvas->m_layers.clear();
                 canvas->m_canvas->m_order.clear();
+                canvas->m_canvas->resize(res, res);
                 canvas->reset_camera();
                 ActionManager::clear();