I no longer have Compiz-Fusion running on the LXDE-based computer, named ‘Klexel’.

According to this earlier posting, I had run in to stability issues with my newly-reinstalled Linux computer, which I name ‘Klexel’. Well, the only sensible way, finally, to solve those problems, was to deactivate ‘Compiz Fusion’, which is a special window-manager / compositor, that creates a desktop cube animation, as well as certain other effects, chosen by the user out of a long menu of effects, but which needs to run on the graphics hardware, using OpenGL.

Even though Compiz Fusion is fancy and seems like a nice idea, I’ve run in to the following problems with it, in my own experience:

  • Compiz is incompatible with Plasma 5, which is still my preferred desktop manager,
  • If we have a weak graphics-chip, such as the one provided on the computer named ‘Klexel’ using ‘i915 Support’, trying to run Compiz on it forces the so-called GPU to jump through too many hoops, to display what it’s being asked to display.

Before a certain point in time, even a hardware-accelerated graphics chip, only consisted of X vertex pipelines and Y fragment pipelines, and had other strict limitations on what it could do. It was after a point in time, that the “Unified Shader Model” was introduced, whereby any GPU core could act, as a vertex shader core, as a fragment shader core, etc.. And after that point in time, the GPU also became capable of rendering its output to texture images, several stages deep… Well, programmers today tend to program for the eventuality, that the host machine has ‘a real GPU’, with Unified Shader Model and unlimited cores, as well as unlimited texture space.

The “HP Compaq DC7100 SFF”, that has become my computer ‘Klexel’, is an ancient computer whose graphics chip stems from ‘the old days’. That seems to have been an Intel 910, which has as hardware-capability, direct-rendering with OpenGL 1.4 , the Open-Source equivalent of DirectX 7 or 8 . Even though some Compiz effects only require OpenGL 1.4 , by default, I need to run the computer named ‘Klexel’ without compositing:

screenshot-from-2018-09-04-11-56-50

Also, before, when this was the computer ‘Walnut’, it actually still had KDE 3 on it! KDE 3 was essentially also, without compositing.

It should finally be stable again, now.

By comparison, the computer which acts as Web-server and hosts this blog, which I name ‘Phoenix’, has as graphics chip an Nvidia “GeForce 6150SE”, that is more powerful than the Intel ‘i915′ series was, is capable of OpenGL 2.1 , equivalent to DirectX 9 , but still predated the Unified Shader Model chips. Microsoft has even dropped support for this graphics chip, because according to Microsoft, it’s also not powerful enough anymore. And so up-to-date Windows versions won’t run on either of these two computers.

(Update 09/04/2018, 18h20 : )

I have come across some surprising facts about the Intel i915 Graphics Chip Family. Apparently, It is supposed to support OpenGL 2.1 , just like the other graphics chip, which I was comparing it to. At the same time, the ‘glxinfo’ command when run on the computer named ‘Klexel’, reports just that.

The conclusion which I need to come to is that, rather than the OpenGL version of the hardware not being high enough, this might just be an embarrassing case of the Debian drivers being shoddy. What can happen is that due to badly-programmed drivers, corrupted bits can end up stored on the graphics chip, which eventually cause it to fail at rendering something. It’s just that in the case of desktop compositing, what the chip next fails to render, could be the desktop cube itself, or the virtual camera position from which it’s to be made visible on the actual monitor. OTOH, if individual applications employ direct-rendering, the worst that can happen, is that one application-window gets messed up, until that application is closed and restarted.


 

I suppose that a different question which the reader might ask could be, ‘Does it pose any problems on the computer named Klexel, that even without compositing, some of its GUI libraries, especially Qt5 , require direct rendering?’ And the answer I’m getting is ‘No.’ Direct-rendering parts of the Web-browser’s view, or of Libre Office windows, piece by piece, poses no problem, just like, displaying the Compiz Fusion desktop cube, posed no problems at first. At first, that compositing configuration seems to recognize the graphics hardware and runs. Only, with Compiz, eventually some glitch gets the better of the computer – and the user.

Dirk

 

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