one last bit of iterator weirdness

[Cyrille Berger Skott]

On Thursday 26 Apr 2012, Boudewijn Rempt wrote:
> I still cannot explain what is going on here exactly, there's a huge lack
> of documentation in this area, but I managed to "fix" it...

I guess there is a transaction running on that srcDev. The question is whether 
you can use a non const iterator (and the conscequences for that). Otherwise I 
suggest adding the following method to the const iterator interface:

const quint8* constRawData() const;

The idea with not having it was that const iterator would be used on devices 
where old tile == new tile.

-- 
Cyrille Berger Skott