Command Design in the CAD Software

There are many human-computer interactions in CAD software. Many commands have to be completed with many steps and the users have to remember lots of commands and parameters. It designs the system frame based on MVC pattern and command pattern for single step interaction software. After the users select entities or snap points, the commands matching the selection will be judged. The users´ behaviors are predicted based on the previous pattern. And the behaviors history is saved and reloaded for undo/redo and operations playback.