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Identifier uch.csd.msc//1993MST0205
Title Σχεδιασμός και Υλοποίηση του Μηχανισμού Undo-Redo στον Λαβύρινθο
Alternative Title Design and Implementation of Undo - Redo mechanism in Labyrinth System
Creator Farsaris, Jason E
Abstract To err is human. A practical software system must take in account the fact that its users will make various sorts of mistakes during the use of the system. If no protection against errors is provided, the system is very likely to be abandoned. This paper deals with the design and implementation of complete undo - redo mechanism in Labyrinth system. 'Labyrinth' is a general - purpose, open core for building graphical anb CAD tools. Provides a set of mechanisms for drawing graphical entities and for managing hierarchical networks of interconnected, parametrized cells. We described the design of the undo - redo mechanism in Lady's kernel, according to the object - oriented model. The undoable commands are mainly the ones, which manipulate the cells' definition structure. The user can recall one or more commands in reverse order in which the were executed. He/she can also reexecute one or more undome commands. Furthermore, we present the data structures (undo stacks), in which the undo/redo information for each undoable command is kept. Undoing/redoing comes in many flavors: Cummulative undo/redo, global undo/redo, undo/redo per composite cell. Under special circumstances undo or redo fails (mechanism comes in "blocking" state. Finally we present some ideas for improving abd expanding the mechanism (interrupt mechanisms).
Issue date 1993-05-01
Date available 1997-06-2
Collection   School/Department--School of Sciences and Engineering--Department of Computer Science--Post-graduate theses
  Type of Work--Post-graduate theses
Views 466