conditional os in UI xml, add system dialog file open on osx, check api format or error message when opening a document, per-char text wrap on NodeText, additional info on create doc dialog like working path

src/node.cpp

@@ -866,6 +866,17 @@ void Node::load_internal(const tinyxml2::XMLElement* x_node)
     auto x_child = x_node->FirstChildElement();
     while (x_child)
     {
+        if (auto os = x_child->Attribute("os"))
+        {
+            auto osv = split(os, ',');
+            if (std::find(osv.begin(), osv.end(), PP_OS) == osv.end())
+            {
+                LOG("Element %s not for this os(%s), skipping", x_child->Name(), PP_OS)
+                x_child = x_child->NextSiblingElement();
+                continue;
+            }
+        }
+
         kWidget child_id = (kWidget)const_hash(x_child->Name());
         switch (child_id)
         {