[Drawkit] Drawing Changed Indicator?

[Allan Daly]

Thanks for the reply and your good advice, Graham. I was wondering if  
undo was the way to go and it sounds like it is. I will follow that  
approach -- sounds like it should be relatively straightforward. -Allan


On Feb 5, 2010, at 1:07 AM, Graham Cox wrote:

> Hi Allan,
>
> Are you using any form of Undo? If so, that's probably the easiest  
> way to tell - if there is anything to undo, there are unsaved  
> changes. This is essentially how NSDocument works as well - it  
> receives notifications from the undo manager which drive the save  
> change status.
>
> If you're not using Undo, it's going to be a lot trickier, since DK  
> in itself doesn't have much of a concept of 'unsaved', as it is not  
> responsible for saving apart from supplying the data to be saved  
> when requested. It might be possible to observe objects via KVO and  
> track changes that way but it's not going to be very  
> straightforward. Really, undo is the only object that is informed  
> for all possible changes that occur. If you don't want to use undo  
> you could still set a private undo manager and receive notifications  
> from it, perhaps settings it history length to 1 (the minimum length  
> possible) to avoid it accumulating too much stuff in memory.
>
> --Graham
>
>
>
> On 05/02/2010, at 5:24 PM, Allan Daly wrote:
>
>> Hi Graham,
>>
>> I'm using DK drawings and views in my application and I'm at a  
>> point where it would be useful to be able to know if a user has  
>> changed the content or configuration of a drawing such that it  
>> needs to be saved. Is there a way to look at the properties of a  
>> drawing or drawing view and find out if the drawing has been  
>> changed since the last save?
>>
>> I'm not using DKDrawingDocument objects -- just straight DKDrawings  
>> and DKDrawingViews.
>>
>> Thanks for any ideas you might have.
>>
>> -Allan
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