Re: [Rosegarden-devel] [Guitar Chord Editor] - Adding new command

[Chris C. <chr...@fe...>]

G:
> This pattern is very simple : all user commands are represented by 
> instances of an abstract Command class, which has only two methods : 
> execute() and, obviously, unexecute(). 

Note that some of our commands use an intermediate class (BasicCommand) to provide unexecute. This basically implements a brute-force undo for commands that modify part of a Segment - at construction time the command indicates what region of the segment it will modify and the class saves a copy of the events in that region, restoring them on unexecute. 

It can optionally implement execute() the same way on all but the first invocation (brute-force redo).

This class is where the modifySegment method originates. 


Chris