#278 Xscreensaver rendering four quarter-size images on screen

Rendering Error
MGA OpenGL (56)

I have noticed a rendering problem with Xscreensaver demos.

All the OpenGL screensavers are rendering four small images across the top of the screen, instead of full-screen.

It's probably going to turn out to be a bug in xscreensaver or the coding of the demos, but there again these were working fine until recently.

Anyway the images are subtly different in colour, but bizarrely, the colours match between the first and third images, and between the second and fourth. Still seems to be accelerated, as stairs (for example) is still fairly quick (this particular one seems to be treacle-slow in software, as is lament).

It struck me (just a guess) that somehow the CRTC and the accelerator have got into different "modes" having their parameters such as bit depth or buffering slightly different.


  • Bill Crawford

    Bill Crawford - 2001-01-12

    This doesn't happen in software fallback mode, so I think there is an issue with DRI here.

  • Bill Crawford

    Bill Crawford - 2001-01-13

    I just found out this is being triggered by a setting in the xscreensaver-demo program which appears to be forcing the window to be created with an inappropriate Visual for DRI rendering to take place.

    However I would still consider this a bug as the driver is attempting to render directly into a window with the wrong Visual and making a bit of a mess in the process.

    I have been unable to get a screenshot, but I have verified that this happens with at least two libGL.so versions.

    This is the mga.o kernel module from XFree86 CVS about five days ago, XFree86 likewise.

    Weirdest part is that it looks like the bits being drawn to screen may be the depth buffer ... sproingies looks like it's seen from behind.

  • Brian Paul

    Brian Paul - 2001-01-24
    • assigned_to: nobody --> jhartmann
  • Brian Paul

    Brian Paul - 2001-01-24

    Just a note: I've reproduced this problem on my machine using
    demos/texcyl and samples/prim demos. Jeff will try to look
    into it.

  • Bill Crawford

    Bill Crawford - 2001-02-19

    Still happening with latest CVS ...

  • Bill Crawford

    Bill Crawford - 2003-09-25
    • status: open --> closed

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