Session Manager Service
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The Session Manager Service is a graphical-based service used in EiffelStudio to persist and retrieve data between multiple sessions of EiffelStudio. The session manager (SESSION_MANAGER_S) provide access to state persisted sessions in four flavors; Environment, Per-Window, Per-Project and finally Per-Window/Per-Project. The fine grained control of session states proffers a mechanism needed to restore the EiffelStudio as it was left as well as restore a project to exactly how it was left when it was closed.
Preferences Vs. Session Data
The session manager service is very simple to use and supports arbitrary data types so you may want to jump right in an use it instead of the defining a configurable preference. Session data and preference data have different roles so it is important you choose the right method of data persistence for the task you are trying to perform.
Both session data and preference data are persisted between opened and closed sessions of EiffelStudio, which is the extent at which the are akin. Session data will never been seen by the user whereas preference data can be viewed and modified from within the EiffelStudio IDE. It would not be wise to store a discardable dialog prompt's discarded state in a session because the user may want to revert back to view the dialog prompt at a later time - this is a clear case for a preference. On the other end of the scale, storing a tool's tool bar toggle button's selected state would be ideal to store as session data instead of preference data. That said, storing a toggle button's state in session data might not applicable for the task it's to perform. Note the reference to a tool's tool bar button. A tool is general self-contained and should not affect the behavior of other parts of EiffelStudio. Tool bar buttons on the main tool bar, which actually affect EiffelStudio as a global entity generally should not use a session but a preference instead. The exception to this rule is if data needs to be persisted on a per-window or per-project level.
