The problem is still there. KDE4 svn of yesterday, build myself, on gentoo.
I can clearly see the difference in selection speed between dolphin and konqueror on my system (core duo cpu and nvidia 7300go gpu). KWin compositing (3d effects) makes no difference.

To reproduce :
open dolphin, go to a folder with some images, activate "preview", drag the rubberband around -> result : the selection lags quite bad behind the mouse mouvements

open konqueror, go to the same folder, drag the rubberband around -> result : the selection (almost) smoothly follows the mouse

Visually, the two behave identical, it's just the speed that differs.


Imortant : Using a folder with images, with preview on, highlights the speed difference, but the difference exists under all circumstances (even with preview off, in a folder like /lib).


Konqueror uses the dolphin-kpart, so the problem must be in dolphin itself (not the kpart). 

This bug is really annoying, because dolphin gets just to slow to use confortably ...

All this on kde4. With konqueror 4 and dolphin 1 (from kde4).

Thanks Laurens for the report. Could you please let us know:
- which view mode did you use (icons, details, columns)?
- do you have enabled the Information Panel
- do you have enabled Nepomuk?

If the problem does not occur anymore when you close the Information Panel: This issue has been fixed for KDE 4.2.

The slowdown still exists in my kde4.2 trunk checkout from last week.
Nepomuk and the info panel are diseabled.
It has gotten better, but most rubberbandings are still slower in dolphin than konqueror (in iconview).
It is not very reproducible though, sometimes it's slow, sometimes it's ok. But whenever it slows down, Xorg cpu usage skyrockets. Fortunately most of the slowdowns are just a slow painting fps, without input lag (that certainly is an improvement over kde4.1)

However scrolling an iconview window with 4000 items gives some serious slowdowns in both konqui and dolphin, and this puts Xorg on 90% cpu use, so I guess the nvidia video driver is at it again...  You probably can't do anything to fix this (quite some qt4 paintops are real slow here on my 7300go with binary nvidia driver).

The same stuff is supersmooth on another laptop with an ati 3650 video card.

OK, I'll have a look whether there are still expensive operations done in Dolphin although the Information Panel is disabled...

SVN commit 886635 by ppenz:

don't request a tooltip during a selection

CCBUG: 151496

 M  +5 -4      tooltipmanager.cpp  


WebSVN link: http://websvn.kde.org/?view=rev&revision=886635

SVN commit 886642 by ppenz:

assure that no expensive operations are done when the Information Panel has been opened at least once and closed again

CCBUG: 151496

 M  +4 -4      infosidebarpage.cpp  


WebSVN link: http://websvn.kde.org/?view=rev&revision=886642

I did some profiling with valgrind: There seems to be no bottleneck in the Dolphin application specific parts, so Konqueror and Dolphin should (...) be equally fast. I also could not observe the behavior that Konqueror feels faster on my environment :-/

But during the profiling I observed 2 things:

1. Tooltips get requested during the selection. I've committed a fix (see comment #6). However this took only around 5 % of the overall performance.

2. When the Information Panel is open and has been closed without restarting Dolphin, then still expensive operations are done during a selection (generating of previews, getting meta data). I've fixed this (see commit #7) and this might be the root cause during your testing.

I cannot do anything against the X11 issues (I've also an NVidia card and the selection itself is very slow), however I hope that you can confirm that Konqueror and Dolphin are now equally fast/slow ;-)

I've set this issue to FIXED, please reopen it if it still occurs after updating to the latest NVidia driver. Thanks!