Can I set a fixed root path to the Open Workspace widget?

In my customized Theia, I want the user can only open some designated folders, so can I set a fixed root path to the Open Workspace widget? Or how can i do that? Please help, thanks.

[original thread by AlwaysMing]

@ppeiming-mo you can rebind your own implementation for WorkspaceFrontendContribution and override the method doOpenWorkspace() to accept a fixed path (ex: the initial path) to something your use-case requires.