Possible problems with Intel drivers in 4.5.0 release
Helio Chissini de Castro
helio at kde.org
Tue Aug 3 01:57:00 CEST 2010
Martin, what you need to test ?
I have a notebook with this current issue ( Fedora 13 ) and happens that even Meego SDk not works anymore,
so is indeed a Intel issue.
I have another machine to test, desktop, but remote one.
Em Segunda-feira 02 Agosto 2010, às 15:59:24, Martin Gräßlin escreveu:
> Hi Release-Team,
> I know that the release is scheduled for tomorrow, nevertheless I want to make
> you aware of a possible problem with Intel graphics cards and compositing.
> I think I first have to explain a little bit: KWin uses a test to determine if
> OpenGL compositing is working during the startup. This seems to fail for some
> Intel drivers since some time. It used to work and the code has not changed,
> so it is most likely a driver bug. I was first made aware of this problem at
> Akademy. Due to the fact that I do not own Intel hardware I was unable to
> reproduce or try to fix the issue.
> Up to 4.4 KWin just disabled compositing if this check during startup failed.
> In the 4.5 development cycle it was changed to fall back to XRender
> compositing. The idea behind it was that you get translucancy when starting
> from live cd or running in a virtual machine. It was not meant for the case
> that the OpenGL driver causes an incorrect self check failure.
> This fallback to XRender causes slowness of the system and some effects not
> working. Furthermore the complete UI says that it is using OpenGL compositing
> although in truth XRender is used.
> When I was made aware of this problem with Intel drivers I reverted the
> fallback to XRender both in trunk and branch (svn revs 1148315 and 1148316).
> Unfortunately I missed one change (the original commit changed more than just
> the fallback) which I found by pure luck this weekend (svn commit 1157978).
> It's confirmed that this commit is now finally working: compositing is
> disabled at startup. By disabling the functionality checks in the advanced
> compositing preferences it is possible to get OpenGL compositing working
> Now the question is what to do with this commit. Due to the fact that I missed
> this one line KWin is now saying that it disables compositing but in truth is
> falling back to XRender. I see three possible solutions:
> 1. We ignore it. This might result in many complaints about slow KWin and that
> effects are not working any more (e.g. cube, coverswitch, blur, etc.). We will
> have many complaints about slow KWin anyway due to the enabling of blur and
> the fact that many drivers are too bad for it. On the other hand we had no bug
> report to this issue. I only heard about this problem by fellow KDE
> developers, which might be related to the fact that we have more recent
> drivers/Xorg than most of our users.
> 2. We backport this patch to 4.5.0. This means a lot of work due to the
> schedule (sorry for writing that late, I had to think about this issue for one
> day) and will cause users not be able to use desktop effects any more. But it
> would be the cleanest one.
> 3. We backport to 4.5.1. This would mean a behavior change between 4.5.0 and
> 4.5.1 which I would not like.
> To summarize: I am not happy with any of the three options I came up with. And
> I do not know what to do about it. Given that the release is tomorrow I guess
> it's only possible to choose between option 1 and 3, while I think option 2
> would be the best. I think it's better to disable compositing instead of slow
> compositing. So the question is, if we should backport the commit for 4.5.1.
> The best solution would be to fix the failing self check. But due to missing
> hardware I am not able to investigate it.
> Sorry for writing that late
> Martin Gräßlin
Helio Chissini de Castro
South America and Brazil Primary Contact
KDE Developer since 2002
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