Martin Graesslin looks at problems with the interaction between KWin and some graphics drivers. "Now that I have explained all our checks we did to ensure a smooth user experience, I want to explain how it could happen that there are regressions in 4.5. In 4.5 we introduced two new features which require OpenGL Shaders: the blur effect and the lanczos filter. Both are not hard requirements. Blur effect can easily be turned off by disabling the effect and the lanczos filter is controlled by the general effect level settings which is also used for Plasma and Oxygen animations. Both new features check for the required extensions and get only activated iff the driver claims support for it. So everything should be fine, shouldn't it? Apparently not when it comes to the free graphics drivers (please note and remember: we do not see such problems with the proprietary NVIDIA driver!)." (Thanks to Jos Poortvliet)