Will KDE drop support for older graphics chips?

Martin Gräßlin, lead developer of the compositing window manager KWin, has been considering the future of OpenGL 1.x support in KWin in a blog entry titled "The costs of supporting legacy hardware". He is considering removing the code because almost all modern graphic chips and drivers support the more recent OpenGL 2.0.

Gräßlin began considering the issue after seeing that Apple is dropping some support for legacy hardware in its next release on Mac OS X, 10.8. For the first time, Apple is dropping support of hardware on the basis of the GPU, rather than the processor. Gräßlin classifies legacy hardware as "anything not supporting at least OpenGL 2.0"; to use such an outdated chip requires separate code paths in KWin and the optimisation of legacy paths might "decrease the quality of the overall system".

Support for OpenGL 1.1 hardware therefore leads to increased complexity and higher maintenance costs. OpenGL 2.0 has been supported, according to Gräßlin, on ATI/AMD since the R300 (Radeon 9500) in 2002, on NVIDIA since the NV40 (GeForce 6) was released in 2004, and on Intel since the I965 released in 2006. OpenGL 2.0-supporting chips have been on the market for at least six years and the alternative graphics system Wayland will be unlikely to do anything with the legacy hardware.

However, there would be issues removing the OpenGL 1.x related code – the removal could affect many systems with Intel graphics cores and users of proprietary graphics drivers from AMD would have to forego a lot of KWin's 3D effects. "Given that the radeon driver has no problems with OpenGL 2 on the same hardware, I would not mind removing support for proprietary drivers", says Gräßlin. One thing Gräßlin says it would not affect is low end hardware; he points out that, for example, OpenGL ES 2.0 shares much of its code with the OpenGL 2.0 code path.

A solution for owners of legacy hardware may be the optimised infrastructure around the Mesa 3D llvmpipe driver. The driver performs its 3D acceleration entirely in software but it can already be used with Fedora 17 for smooth graphics in the GNOME shell. He wants to evaluate the effectiveness of the llvmpipe drivers with KWin when Mesa 8.0 arrives and "if I am satisfied with the performance, I will be tempted to remove the OpenGL 1.x based legacy code..."

(djwm)