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backend/drm: implement output layers #3095
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The ad-hoc copies of I'll refactor the DRM backend a bit to avoid doing such copies. |
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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. The goal is to make use of this API in a future scene-graph API. References: swaywm#1826
The output layer API is implemented using subsurfaces. I chose to implement this API in the Wayland backend before doing so in the DRM backend, because it's way easier on Wayland. On DRM, one needs to figure out how buffers can be mapped to KMS planes (libliftoff can help) and perform atomic test-only commits (our current DRM backend isn't ready for this).
This new example demonstrates how to use the wlr_output_layer API. It's
a compositor that displays all client surfaces using wlr_output_layer.
To test, one can for instance run:
build/examples/output-layers -s 'weston-simple-dmabuf-egl & weston-simple-egl'
Under the Wayland backend (where layers work as long as clients use
DMA-BUFs), this should display two surfaces with remote wl_subsurfaces.
"state" is easily confused with wlr_output_state.
Previously, we were copying wlr_output_state on the stack and patching it up to be guaranteed to have a proper drmModeModeInfo stored in it (and not a custom mode). Also, we had a bunch of helpers deriving DRM-specific information from the generic wlr_output_state. Copying the wlr_output_state worked fine so far, but with output layers we'll be getting a wl_list in there. An empty wl_list stores two pointers to itself, copying it on the stack blindly results in infinite loops in wl_list_for_each. To fix this, rework our DRM backend to stop copying wlr_output_state, instead add a new struct wlr_drm_connector_state which holds both the wlr_output_state and additional DRM-specific information.
TODO: - Make it work on multi-output setups - Make it handle VRR and gamma
This will be useful for implementing the output layers API.
Delegate all of the work to libliftoff.
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wlroots has migrated to gitlab.freedesktop.org. This pull request has been moved to: https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/3095 |
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Depends on #1985
Depends on #3100