Rendering Issues

I’ve run Kubuntu on an old MacBook Pro (revision 5.1) for over a year now, and it has worked great. However, last week, it became more or less unusable. It seems that some sort of blending operation results in noise.

When using the machine with some composition effects, it was completely unusable – moving a window resulted in a square or static noise. All edges of plasma widgets where covered in noise, etc. Disabling all effects meant that I can use the machine again, however, some noise prevails.

As you can see from the screenshot at the top of this post, it is visible in the panel. It is also visible in elements such as the slider and the upper right corner of the desktop folder plasma widget. Another factor is that the noise sometimes disappear when a repaint is forced, but it is “physical” enough to get caught in a screenshot.

So, dear lazy web, do you recognize this from somewhere? Is it the drivers? Is it something in kwinrc? Or is it hardware (perhaps graphics memory) failing?

Update. Thiago from Tro^H^H^HNokia Qt Development Frameworks^W^W^W^WIntel (apparently at a new job) told me to clear the image caches. Read the comment, follow the instructions, and everything works again!

6 thoughts on “Rendering Issues”

  1. I have seen this problem, with NVidia cards. They may happen on other cards, but NVidia is what I had when the problem happened.

    The problem is either driver or hardware. Either way, there’s a software crash in the GPU and it produces bad results. You may see some cryptic warnings in your dmesg, on lines starting with NV and containing a lot of hex numbers that are probably meaningful to NVidia people only.

    The solution to this is to do a cold reboot, update your drivers (downgrade if you’re using a beta driver) and clear all of your KDE image caches.

    The image corruption may have crept into your Plasma theme cache and the general KDE icon cache, due to the rasterisation being done with GPU acceleration. That’s why you see this error even with composition turned off.

    Caches are located in $KDEVARTMP and $KDEHOME/cache-$HOSTNAME.

  2. I’ve seen menu, font and icon corruption too many times with a radeon card and the gallium driver. It is relatively easy to trigger in my case; simply scroll through a fairly large PDF file with okular. Some times the corruption makes the system unusable. I don’t think it is KDE related, because I’ve seldom seen images in Firefox become corrupted too, so this points to a driver/Xorg issue.

  3. I’ve had this problem as well on my hardware, to me it seems they leave a much to large svg-canvas in the theme files which in most cases just waste hard-drive space by the amount necessary. A fix is in order IMO. Calledonia uses about 80% the space default theme does and the icons look better at all times!

  4. Please make sure to file a bug report. No user should have to do this themselves.

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