Recently noticed the View.SetCategoryHidden(Category category, bool hide) in the Revit API 2017. It looks pretty interesting or odd, that most people may think.
It is not new. Its intention seemed to replace the old View.SetVisibility(Category category, bool visible). Not only its method name has been changed, but also its parameter meaning. It is normal to change an existing method name or fix a typo there for example. It is also normal to introduce some more parameters with software being big and more features added.
In this case, the parameter amount is the same, two as before. The second parameter means totally opposite than before. Before, it means to make the category visible but now to hide the same guy. So it is really a Hide and Seek game!!!
Nothing big from changing so from the API, but it would cause great trouble for application migrations. It is not as easy as Search & Replace All. Please be careful, guys!