kde4 customize taskbar redraws multiple times

[Kevin Hunter]

Binary package hint: kdebase-workspace

Setup:
 Dell Vostro 1500, Core 2 Duo, nVidia GeForce 8400M (not currently used)
 Installed Hardy alpha 6, Kubuntu-KDE4

To save someone 5 minutes of head scratching, I'll repeat: that's KDE4, not KDE3. However, looking through the /etc/init.d/kdm script, I see references to kde3, so not sure ... Konqueror->Help->About reports 4.0.2

I probably noticed the inefficient/multiple drawings because I am not currently using my video card. I do, however, have a very fast system so this shouldn't be so obvious.

Symptom: changing location of taskbar panel makes desktop redraw multiple times. On this 2.2 GHz Core 2 Duo machine w/ 2G RAM, it takes a noticeable 3-5 redraws and 8 or 9 seconds to finish.

Steps to reproduce:
1. Right-click on taskbar, choose "Panel Settings"
2. Change location of panel to orthogonal place. e.g bottom to left or right. (Top doesn't trigger it as noticeably.)
3. Click Apply.
 ... Screen will redraw multiple times ...

Expected results: Desktop should redraw once, and only once, in a second buffer and refresh the visible screen only once.

Suggestion 1: Disable your video card to really highlight inefficient behavior.
Suggestion 2: Also have another process hog the CPU(s) to really highlight the inefficient behavior.

I note that after having changed the panel location three or four times (to make sure that I can reproduce this behavior), the kdm program is now hogging a core. I'll make two more bugs for that, about kdm hogging cpu at all, and kde/kernel not utilizing second available core.

[Kevin Hunter (hunteke)]

By orthogonal I mean top or bottom goes to left or right, and left or right goes to top or bottom. I suspect that changing both horizontal and vertical width of desktop is taking some long code path.

[Kevin Hunter (hunteke)]

For my Suggestion 1, I guess that "disable" is a misnomer. I mean simply that I'm not using the proprietary driver. Actually, I'm not sure *what* driver I'm using. I can attach my xorg.conf if that would be helpful. Other explicit information that may be helpful:

<code>
$ grep -i nvidia /etc/X11/xorg.conf
   # [No results]
$ grep -i nv /etc/X11/xorg.conf
   # [No results]
$ uname -a
Linux hani-alpha 2.6.24-12-generic #1 SMP Wed Mar 12 22:31:43 UTC 2008 x86_64 GNU/Linux
</code>

But, whatever driver I'm using, it's still an inefficient drawing process.

[Jonathan Thomas (echidnaman)]

I can confirm this in the latest Hardy. I believe that the problem is that all the widgets in the panel are all scrambling around, adjusting to the different layout. Many of these said widgets also adjust quite poorly to the different position.

[Jonathan Thomas (echidnaman)]

Things are much better in KDE 4.1.2 in Intrepid.