Render Refactor
This is an overview task.
Definition of Render
When talking about the backends of KWinFT we usually mean the display backends, that is how graphics are transferred to other deeper areas of the system to finally show for the user (that being said there is also an input backend on Wayland connecting to libinput).
To render an image and afterwards to display it are usually two different steps that can even be on different silicon in hardware. In general to render means to create the image while to display means to output it.
When we say we want to do a render refactor then this would mean to work on the first step where we create the image. Mind you this creation must be done in a way so it is afterwards possible to easily hand it over to the display backends, so we might rather want to call it a refactor of our rendering pipeline.
What we don't mean with rendering is the actual manipulation of the image, which is part of the effects system, but rather we mean the plumbing behind the scenes to enable this.
Goals
In specific items we want to refactor our rendering pipeline according to the following strict requirements:
- Multi-rate refresh composition on Wayland.
- Adaptive sync support on Wayland.
- Direct scanout of any wl_surface to a hardware plane.
- Keeping the X11 render pipeline functional without regressions.
- Prepare for a library split-out of the rendering code according to #21.
- Replace dynamically loaded plugins with compile-time switches to select the render pipelines that should be available at runtime.
We also try to follow the following soft requirements:
- Reduce the amount of code we provide ourselves and rather use other well-tested pure C/C++ libraries.
- But reduce Qt usage.
- Use more static inheritance.
- Provide composite unredirect on X11.
Plan
Internal
- Clean up backends, simplify code. Early attempt at that in this branch.
- Design the overall future structure without plugins and with less dynamic inheritance in form of an UML or C4 diagram.
Reaching out
See how we could depend on wlroots in our rendering and display code. wlroots provides most of the features we want to have already and it is a well-organized project with respected developers.
wlroots is used in other interesting compositor projects like Wayfire. There is potential for sharing the work load and increased collaboration in the future.
