Add a src_box state field. Use the SRC_* KMS props in the DRM
backend, reject the layers in the Wayland backend (for now, we can
support it later via viewporter).
This allows callers to set a destination size different from the
buffer size to scale them.
The DRM backend supports this. The Wayland backend doesn't yet
(we'd need to wire up viewporter).
- Simplifies the backends
- Avoids having two ways to do the same thing: previously one could
disable a layer by either omitting it from wlr_output_state.layers,
or by passing a NULL buffer
- We can change our mind in the future: we can allow users to omit
some layers and define a meaning without breaking the API.
References: https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/4017#note_1783997
This is based on previous work [1] [2].
This new API allows compositors to display buffers without needing to
perform rendering operations. This API can be implemented on Wayland
using subsurfaces and on DRM using KMS planes.
Compared to [1], this approach leverages wlr_addon_set to let backends
attach their own private state to layers, removes the pending
state (necessary for interop with wlr_output_commit_state()) and
enum wlr_output_layer_state_field.
[1]: https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/1985
[2]: https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/3447
Alexander Orzechowski
Simon Ser