This is the first tiny step towards the layer-based compositing in kwin.
The RenderLayer represents a layer with some contents. The actual
contents is represented by the RenderLayerDelegate class.
Currently, the RenderLayer is just a simple class responsible for
geometry, and repaints, but it will grow in the future. For example,
render layers need to form a tree.
The next (missing) biggest component in the layer-based compositing are
output layers. When output layers are added, each render layer would
have an output layer assigned to it or have its output layer inherited
from the parent.
The render layer tree wouldn't be affected by changes to the output
layer tree so transition between software and hardware cursors can be
seamless.
The next big milestone will be to try to port some of existing kwin
functionality to the RenderLayer, e.g. software cursor or screen edges.
Having a render loop in the Platform has always been awkward. Another
way to interpret the platform not supporting per screen rendering would
be that all outputs share the same render loop.
On X11, Scene::painted_screen is going to correspond to the primary
screen, we should not rely on this assumption though!
Hardware constraints limit the number of crtcs and which connector + crtc
combinations can work together. The current code is searching for working
combinations when a hotplug happens but that's not enough, it also needs
to happen when the user enables or disables outputs and when modesets are
done, and the configuration change needs to be applied with a single atomic
commit.
This commit removes the hard dependency of DrmPipeline on crtcs by moving
the pending state of outputs from the drm objects to DrmPipeline itself,
which ensures that it's independent from the set of drm objects currently
used. It also changes requests from KScreen to be applied truly atomically.
Once in a while, we receive complaints from other fellow KDE developers
about the file organization of kwin. This change addresses some of those
complaints by moving all of source code in a separate directory, src/,
thus making the project structure more traditional. Things such as tests
are kept in their own toplevel directories.
This change may wreak havoc on merge requests that add new files to kwin,
but if a patch modifies an already existing file, git should be smart
enough to figure out that the file has been relocated.
We may potentially split the src/ directory further to make navigating
the source code easier, but hopefully this is good enough already.
