Helper to generate previews of resources or files. This object is used to generate previews for resources of files. [b]Note:[/b] This class shouldn't be instantiated directly. Instead, access the singleton using [method EditorInterface.get_resource_previewer]. Create an own, custom preview generator. Check if the resource changed, if so, it will be invalidated and the corresponding signal emitted. Removes a custom preview generator. Emitted if a preview was invalidated (changed). [code]path[/code] corresponds to the path of the preview.