The Chat window should be pretty straight forward. The only problem may be implementing the connection between computers. But the UI and functionality seem simple enough.
One tricky part for the Roster to be implemented is when granting Snapshot permission, the instructor selects a Snapshot and then click on the checkboxes. A connection between the Roster and Deskdrawer needs to be established. Also, sending chat signals to the Chat window and creating groups needs careful implementation as starting chat tabs is one of the main functions for Roster.
The Editor object is comprised of three main components: Numbering, Folds, and HTMLContent. Numbering is used to keep track of the number of lines in the lecture and the current line the cursor is at. Folds are used to store areas that may or may not be hidden from view. Folds and Numbering operations consist of accessors and mutators methods for every instance variable. HTMLContent is byfar the most important component in that it contains the actual lecture content represented by alternating tags and strings. Operations for HTMLContent are the standard collection operations (addition, selection, modification, deletion). One operation that might be difficult to implement is the "Generate slides" macro operation in which the lecture is broken up into slides. The application will have to "convert" all the content and wrap or break it up so that it stays within the slide limits set by the user. This may get tedious or horribly messy if designed poorly.