preview in dolphin is slow with many pictures

[Mathias Kraus]

Peter Penz schrieb am Monday 30 June 2008:
> Hi Mathias,
>
> I think I've some good news for you :-)

Hi Peter,

just two words ... you rock!

> On Thursday, 12. June 2008 23:46:03 Mathias Kraus wrote:
> [...]
>
> > some suggestions for preview:
> > -start from top left, instead from bottom right, if easy doable
> > -start with images that are completely in the visible area, not only
> > partly, but I think this will be more expensive
>
> [...]
>
> I've spend quite a lot of time during the last days to do some profiling
> and find the bottlenecks for the preview generation. The following
> improvements are now in SVN:
>
> - the previews are always generated for the visible area first from the
> top-left to the bottom-right (no matter which kind of sorting is used)

did I already said that you rock. BTW, I just suggested the top-left to bottom 
right direction because LTR is the natural way in Europe, Kanada, USA and so 
on, but if you get bored sometime and just don't know anything to do in 
Dolphin or any other project you have, I think our friends that are more 
familiar with RTL would enjoy a top-right to bottom-left preview generation 
from row to row and our Asian friends might enjoy a preview generation column 
wise. But that would just be the dot on the i or the cherry on top of the cake 
:)

> - if the previews for the invisible items are generated, the UI is not
> blocked anymore and the generation is done now very fast (even in the
> debugging mode)

Nice. I tried openSUSE on the weekend and noticed that Dolphin was much faster 
than on Kubuntu, e.g. I had absolutely no freeze while opening /usr/bin. I'll 
rebuild trunk for Kubuntu to enjoy the speed improvement also on my day to day 
distribution. BTW, you rock :)

> In my tests when having a folder with 1000 images and scrolling through the
> view during preview generation resulted in no blocking of the UI. Dolphin
> in KDE 4.0.x took 19 seconds for generating previews of 772 images (release
> mode) and Dolphin for KDE 4.1 only takes around 4 seconds (debug mode) for
> the same task although nicer (and more expensive) image frames are drawn
> and the visible area is considered too.

Did I already mentioned that you rock. I don't know, but while I was a student 
my memory got worse from semester to semester. I guess it's because of the 
huge amount of information ... I'm sure it can't be the huge amount of beer :)

> I did also some tests with a folder having 10000 items and here some
> blocking is done when opening the folder or after moving the visible area,
> but the root here is a combination how QListView receives the maximum size
> of an item and how Dolphin calculates this size and not the preview
> generation itself.
>
> However I think this is a good base for KDE 4.1 and hope you'll like it :-)

I definitely like it. Thank you very much for your hard work. I think there are 
also many other users that appreciate the work you do.

Best regards,
Mathias

> Best regards,
> Peter