Comment 112 for bug 278471

Greetings!

I would like to add that I'm suffering the same problem on several machines, with a variety of display controllers - SiS, VIA, nvidia, ATI old and new, Permedia, you name it.

They all have one thing in common: Once flawless, their displays start twitching, flickering, or even cutting out for a second as soon as you run something from KDE4.

Whenever any window border or other KDE related widget is drawn, the twitching and flickering starts. Just scrolling a window about or clicking something in the Kontrol bar gets me a minor earthquake on the screen.

However, if you manage to just draw contents, not windows and widgets, the display calms down to flawless again. For example, you can watch a three-hour movie in fullscreen without a single hickup. MythTV sessions are flawless too, and so are other-window-manager sessions ... exactly for as long as you don't start a KDE application.

That rules out any suspicion of bandwidth constraints for the chipset integrated solutions - and so does the fact that my discretes suffer the same symptoms.

Since all these machines have run on KDE 3.5 without any such symptoms whatsoever, and since they all behave just as flawless as they ever did when not using KDE4 at all, I am very convinced this is a symptom triggered by KDE4.

The boxes are all openSUSE 11.1, originally on KDE 4.1 but now upgraded to 4.2.4 via the official openSUSE "KDE4 reloaded" repository. X video drivers are nv, sis, ati, glint, radeon. Some are 32-bit, some are 64-bit installations.

On some of these I skipped KDE 4.1, on those I did start on 4.1 I had the same symptoms - and sorry, I missed the opportunity to disable that KRandR service before the checkbox for it disappeared.

Now, having some experience in low level display chip programming myself, the idea that frequent monitor redetection is causing this sounds very very convincing to me. I know that for VGA monitor detection, one inherently needs to turn the RGB lines off for a brief moment, and I also know that many monitors do blank out while talking on DDC.

If any further information is needed, or if something needs a trial run, please let me know.

First thing I'd like to know, to assist the process, is a way to turn the display detection mechanism off in KDE 4.2 - even if it's an ugly hack, anything goes, just to confirm whether we're barking up the right tree.

Many thanks in advance!

best regards,
Peter