As discussed a few days ago, let's define rotation to be always
clockwise, as it is done in other graphics frameworks as well as our
own image rotation. This means changing the definition for the
software renderer. Also fixed docs for the enum in the linuxkms backend
that was wrong.
This is the initial implementation based on DRM dumb buffers,
which cleans up various things at the same time:
- DRM output is separate from GBM and DRM dumb buffer displays.
The latter two re-use the former.
- The timer refresh for the Vulkan KHR Display rendering lives
now with the KHR display code, in hope to be replaced with a
better mechanism in the future.
What's missing still is support for partial updates as well as
rendering with our own software renderer.
That's less boiler plate for us and better error handling (note how the receive_events()
call on the DRM device now propagates the error). And this also unregisters automatically
on drop.
... instead pass the fd into the calloop event loop and change state when we receive activity on it.
This improves performance slightly, and is a necessary to be able to implement refresh rate throttled rendering (in the next commits).
This patch adds support for the `SLINT_KMS_ROTATION` environment
variable, that instructs the Skia/FemtoVG renderers to rotate
the scene before rendering.
