Re: Attempt for an UNO Undo API

Hi Stephan,

>> I think any kind of error can happen inside an undo implementation for a
>> single action, so I can't think of any reasonable limitation here. A
>> WrappedTargetException might be appropriate, but then again, this is
>> just an euphemism for "anything can happen".
> 
> I see it differently.
> ...
> If an initial undo method has been specified to raise n different 
> exceptions, and it is later found out that an additional exception E' 
> would be needed, there are two choices:
> 
> - E' is of general interest to callers of undo, they would want to react 
> to it in specific ways.  This is similar to detecting that a method 
> misses a parameter:  Extend the method (add the raises-specification to 
> the existing method definition, rendering it incompatibly, or add a new 
> interface with the fixed method), fix up the implementation, fix up the 
> call sites.

Given the hurdles imposed on incompatible API changes, I dare to go this
way - experience shows rarely anybody ever goes through this pain,
"only" for having a clean API. Usually one ends up with throwing, guess,
WrappedTargetRuntimeExceptions (I thus consider the mere existence of
this class a bad hack. Well, a way-too-easy door opener for bad hacks,
that is.).

For the moment, I declared an UndoFailedException, derived from
css.uno.Exception, and let undo/redo throw it. Still an euphemism for
"anything can go wrong", though, so I am not that happy with it ...

Ciao
Frank

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Frank Schönheit | Software Engineer | [email protected]
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