Re: [Traits] dirty trait metadata

Robert Kern wrote:
> On Sat, Sep 6, 2008 at 00:33, Prabhu Ramachandran
> <prabhu@...> wrote:
>> Robert Kern wrote:
>>
>>>> Is there a simple way of doing this?  I know that I could achieve this
>>>> if I implemented x as a Property(Array) but is there an easier way?
>>> I don't think so. The comparison logic is in C
>>> (ctraits.c:setattr_trait), and there are no hooks for this.
>>>
>>> If you only need coarse-grained notifications, you might consider
>>> using an updated Event. This:
>> OK, so I came up with a new trait type that does this nicely with minimal
>> fuss and also does the validation right.
> 
> What's the use case again? For the one you demonstrated (notification
> that an array's contents have changed), I don't think the
> ShadowProperty semantics are particularly the obvious way to do issue
> that notification.

The use case is mayavi's mlab sources.  I'd like the user to be able to say

  obj.mlab_source.x = new_x

That new_x may be the same old x but updated.  I'd rather not have the 
user do obj.mlab_source.updated_x = True or whatever after that.  This 
really isn't about notification that an array's contents have changed. 
It is more of an API issue and a user convenience more than anything.

In any case, I've checked it into mayavi so it doesn't affect anyone and 
it works quite nicely for the mlab source.

cheers,
prabhu