The code definition window is a “helper” window that works in close conjunction with the code editor window by displaying definitions for symbols selected within the code editor. It is actually a near clone of the code editor window, with one big exception: It is read-only and does not permit edits to its content.
The code definition window content is refreshed anytime the cursor position is moved within the code editor window. If the cursor or caret is placed in a symbol/type, the code definition window shows you how that symbol is defined.
The code definition window has reacted to the cursor position by showing the source code that actually defines the type of the
_state field. You can see from the figure that ...