Returns whether the region is visible. A region is "visible" if it has been explicitly shown (or not explicitly hidden) and its parent is visible (that is, all of its ancestor frames (parent, parent's parent, etc) are also shown).

A region may be "visible" and not appear on screen -- it may not have any anchor points set, its position and size may be outside the bounds of the screen, or it may not draw anything (e.g. a FontString with no text, a Texture with no image, or a Frame with no visible children).