> On 23 Mar 2016, at 1:23 PM, Graham Cox <graham....@bigpond.com> wrote:
> 
> Hi all,
> 
> I just upgraded to 10.11.4 and XCode 7.3 and therefore the latest SDK. 
> Rebuilding my app, my one instance of IKImageBrowserVIew in my app has gone 
> haywire. Whenever I load new images into it, it scrolls constantly to the 
> bottom of the view. If I manually scroll it elsewhere, it scrolls back to the 
> bottom when I let go. This has worked fine for years, and while I am looking 
> at some new code in this class (and hence have triggered a new compilation of 
> the sources), the new code has no bearing on this issue.
> 
> Has anyone else seen this, and if so, what’s the cause/fix? As it stands, the 
> class is unusable.
> 
> —Graham



So, can anyone suggest a reasonably easy way to investigate this?

I can subclass IKImageBrowserView, but I’m not sure what method I could 
override to get a hook into each scroll of the view (other than drawing, which 
is called too often and in too many other situations to be usable - also I 
believe IKImageBrowserVIew is largely implemented using layers, so it may not 
help).

I could also subclass NSScrollView - this is probably my next approach - but 
I’m hoping there’s an easier way. I need to see what is invoking the scroll of 
the document (image browser) view.

I have been through my code and checked every place that could conceivably 
affect scrolling (such as calls to -scrollToIndex:) and none of these are the 
problem. I’ve tried disabling responsive scrolling, that’s not it. I had one 
exception due to another issue that suggested that this might be being caused 
by repeated calls to -setFrameSize:, but I’ve tried overriding that and it only 
gets called a couple of times - certainly not during this weird scrolling. I’ve 
also determined that the fault stops after some time - in other words If I 
leave the view for enough time, I can manually scroll it where I want without 
it keep jumping back to the bottom. This suggests that there is a 
time-dependent element that is causing this, possibly the background thread 
that is loading all of the image thumbnails. When that’s complete, the 
scrolling stops. But I’ve checked all the places that my code might have a 
bearing on that, and I’ve drawn a blank - my use of IKImageBrowserView is in 
any case fairly simple, in that I pass it the URL of the image and it loads 
that in the background by itself without the intervention of my code.

—Graham



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