With the first Beta for KDE Plasma Workspaces 4.7 out of the door it is time to look back what we achieved in the last half year for the KDE Plasma Compositor and Window Manager. Personally I think this will become a very great release with hughe improvements for our users. The best about it is, that users should not even notice that anything changed at all. Almost everything we did is under the hood improving performance, stability and rendering.
The Compositor received a new OpenGL compositor based on OpenGL 2.x or OpenGL ES 2.0. Our default rendering nowadays uses the programmable pipeline instead of fixed functionality as in 4.6. In order to support the programmable pipeline quite some parts had to be rewritten and got optimized at the same time. Overall this brings a vast performance improvement for all users. From my experience this can even be increased when using the OpenGL ES 2.0/EGL backend which is unfortunately a compile-time switch (as not all drivers and hardware support EGL). I hope that distributions will provide an additional package.
As with all such changes there is the chance that on some hardware/driver combinations the performance decreases due to the raise of requirements to OpenGL 2. If that is the case the user can switch back to the legacy rendering mode by unchecking the option “Use OpenGL 2 Shaders” in the advanced Desktop Effects settings. This will disable all GLSL Shaders. Nevertheless Blur and Lanczos are still useable as they will fallback to ARB Shaders.
Fredrik has done some great work to improve the performance of the blur effect. Effects can know recommend whether they should be enabled by default and for Intel hardware, the effect does not get enabled any more by default. Users can still manually enable the effect. But there is also some real optimization
to ensure that less screen estate gets blurred in each rendered frame and some optimizations
on the shader giving a ~60 % improvement in shader performance with R600G.
Thomas worked on a way to allow applications to block compositing
. The primary goal is to have video players or OpenGL Fullscreen games be able to block compositing as for such use cases compositing is only a bad overhead. We have heard interest from VLC and Wine to support this new flag, but users can even make use of it if the application does not yet provide support for it by using a window specific rule. Given that we have now this new way to suppress compositing we disabled the unredirection of fullscreen windows by default
Together with Jacopo, Hugo and Aaron we worked on adding a new Shadow system allowing to provide their own shadows. This is currently used by Oxygen Qt and GTK to render shadows for so-called unmanaged windows. As the control for the look is with the client, the widget style is able to adjust the shadows for e.g. Mozilla Firefox. Also Plasma is making use of the new Shadows for the Panel and KRunner fixing some annoying issues with the old implementation like window snapping to the panel shadow and clickable shadows in KRunner. Not to mention that the new shadows look way better 🙂 Special thanks to Jacopo for writing the XRender code for the new Shadow system.
Arthur, our GSoC student, did some refactoring already before the GSoC project and brought all outline related code together in one class. This allowed me to add a new Effect to render the outline using a nice looking Plasma FrameSvg. If effects are not active the old X11 code is used. I am looking forward to Arthur’s GSoC, what I have seen so far looks very promising.
Very short before the release we received a Patch from a new contributor, Philipp, allowing KWin to support the graphicssystem raster
. Before KWin enforced the native system. In the beginning I was reluctant to integrate it, but got convinced that this is a hughe improvement. Especially with the NVIDIA blob this is a nice addition as we circumvent the slow transparent filling of XPixmaps improving the performance of resizing windows (caused by decorations) and the effect frames in e.g. Present Windows effect. There are more improvments to come from Philipp like a heap optimization
for glibc in KWin, scheduled for 4.8.
And of course much, much more happened which I just don’t remember at the moment 🙂 And for the next release cycle we can expect more great things to happen, more about that on Desktop Summit
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