Wt

Adding a class to the TreeViewNode uses a WStringStream under the hood. There 'WStringStream::c_str()` is used. This is limited to 1024 characters.

We can omit this dependency, as the styleclasses added by Wt itself, are UTF8, and any styleclass provided by the developer have been added with WWidget::{add/set}StyleClass(). Making them UTF8, and thus not requiring this step again.
The call can thus rely on WStringStream::str(), which is not limited to 1024 characters.