Re: IKImageBrowser performance issues

FROM : Thomas Goossens
DATE : Tue Nov 27 16:02:02 2007

The behavior of the image browser is the following:
When all the visible images are imported (ie. the placeholders are 
replaced by the thumbnail), the browser starts to prefetch some images 
in the neighborhood of the visible area.
This prefetching is asynchronous (in a secondary thread) and with a 
low priority (except if you use the NSImage representation because 
NSImages are not 100% thread safe and so its "decompression" is always 
performed on the main thread).
Which representation are you using ?

> From: Colin Cornaby <colin.<email_removed>>
> Date: 26 novembre 2007 09:26:28 HNEC
> To: j o a r <<email_removed>>
> Cc: <email_removed>
> Subject: Re: IKImageBrowser performance issues
>
> Sorry for the somewhat confusing email, the iPhone is not the ideal 
> platform for typing these sorts of things. :)
>
> Basically what happens is I have a drop down menu to select groups 
> of images to display within the browser view. When the group is 
> switched out, I pull a different batch of items from a backing 
> CoreData database that contains URL's to images. I then tell the 
> image browser view to reload.
>
> After I switch groups, I can watch my app's CPU usage stay extremely 
> high in process viewer, and graphics performance in other parts of 
> my app declines rapidly. The image items in the browser view's 
> currently viewed bounds are all loaded and visible. During this 
> period of high cpu usage I scroll down and quickly run into 
> "unloaded" images, which are represented by whatever the placeholder 
> image is that Apple uses to represent unloaded items. The items are 
> quickly filled in by the browser view.
>
> If I don't scroll down, and I just wait for my CPU usage to hit 0 
> again, I can scroll through the browser view and all my images seem 
> to be already loaded. This is what led me to believe that my image 
> browser was preloaded all the images currently being vended by the 
> datasource, not just the currently visible ones in the data browser. 
> I'm sure some debugging in the data source for my browser would 
> confirm that.
>
> I just find it odd that with IKImageBrowserView being so 
> multithreaded that the browser item loading isn't being handled by a 
> second core, leaving the first core free to continue maintaining the 
> rest of my app.
>
> On Nov 25, 2007, at 9:22 PM, j o a r wrote:
>

>>
>> On Nov 25, 2007, at 5:19 PM, Colin Cornaby wrote:
>>

>>> Do I have any means of regulating IKImageBrowser*s CPU use? It's 
>>> hogging the CPU in my app for a solid 5-10 seconds when I switch 
>>> the items in the view, and I'm not sure the user will understand 
>>> the reason for the CPU hit given that the visible images in the 
>>> view will already be loaded.

>>
>>
>> File a bug report with Apple. I'm not sure why it's loading 
>> "invisible" images at all (are you sure that's what's going on?), 
>> but it seems reasonable to expect that any such activity should be 
>> given a lower priority.
>>
>> j o a r
>>
>>