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
Previously, adaptive sync was just a hint and wouldn't make any
atomic commit fail if the backend didn't support it. The main reason
is wlr_output_test wasn't supported at the time.
Now that we have a way for compositors to test whether a change can
work, let's remove the exception for adaptive sync and convert it to
a regular output state field.
The destroy callback in wlr_touch_impl has been removed. The function
`wlr_touch_finish` has been introduced to clean up the resources owned by a
wlr_touch.
`wlr_input_device_destroy` no longer destroys the wlr_touch, attempting to
destroy a wlr_touch will result in a no-op.
The field `name` has been added to the wlr_touch_impl to be able to identify
a given wlr_touch device.
The destroy callback in wlr_tablet_tool_impl has been removed. The function
`wlr_tablet_tool_finish` has been introduced to clean up the resources owned by
a wlr_tablet_tool.
`wlr_input_device_destroy` no longer destroys the wlr_tablet_tool, attempting to
destroy a wlr_tablet_tool will result in a no-op.
The field `name` has been added to the wlr_tablet_tool_impl to be able to
identify a given wlr_tablet_tool device.
The destroy callback in wlr_tablet_pad_impl has been removed. The function
`wlr_tablet_pad_finish` has been introduced to clean up the resources owned by a
wlr_tablet_pad.
`wlr_input_device_destroy` no longer destroys the wlr_tablet_pad, attempting to
destroy a wlr_tablet_pad will result in a no-op.
The field `name` has been added to the wlr_tablet_pad_impl to be able to identify
a given wlr_tablet_pad device.
The destroy callback in wlr_switch_impl has been removed. The function
`wlr_switch_finish` has been introduced to clean up the resources owned by a
wlr_switch.
`wlr_input_device_destroy` no longer destroys the wlr_switch, attempting to
destroy a wlr_switch will result in a no-op.
The field `name` has been added to the wlr_switch_impl to be able to identify
a given wlr_switch device.
The destroy callback in wlr_pointer_impl has been removed. The function
`wlr_pointer_finish` has been introduced to clean up the resources owned by a
wlr_pointer.
`wlr_input_device_destroy` no longer destroys the wlr_pointer, attempting to
destroy a wlr_pointer will result in a no-op.
The field `name` has been added to the wlr_pointer_impl to be able to identify
a given wlr_pointer device.
The destroy member in wlr_keyboard_impl has been removed. The function
`wlr_keyboard_finish` has been introduce to clean up the resources owned by a
wlr_keyboard.
`wlr_input_device_destroy` no longer destroys the wlr_keyboard, attempting to
destroy a wlr_keyboard will result in a no-op.
The field `name` has been added to the wlr_keyboard_impl to be able to identify
a given wlr_keyboard device.
In case the `wlr_input_device` is not owned by a specialized input device, the
function will finish the wlr_input_device and call it's implementation destroy
function if an implementation has been supplied, or simply free it.
This change introduces new double buffered state to the wlr_output,
corresponding to the buffer format to render to.
The format being rendered to does not control the bit depth of colors
being sent to the display; it does generally determine the format with
which screenshot data is provided. The DRM backend _may_ sent higher
bit depths if the render format depth is increased, but hardware and
other limitations may apply.
Right now, when a new output state field is added, all backends by
default won't reject it. This means we need to add new checks to
each and every backend when we introduce a new state field.
Instead, introduce a bitmask of supported output state fields in
each backend, and error out if the user has submitted an unknown
field.
Some fields don't need any backend involvment to work. These are
listed in WLR_OUTPUT_STATE_BACKEND_OPTIONAL as a convenience.
Instead of passing a wlr_texture to the backend, directly pass a
wlr_buffer. Use get_cursor_size and get_cursor_formats to create
a wlr_buffer that can be used as a cursor.
We don't want to pass a wlr_texture because we want to remove as
many rendering bits from the backend as possible.
The output backend API is now mostly state-less thanks to the atomic
hooks (commit and test). There is one exception though: attach_render.
This function makes the rendering context current. However sometimes the
compositor might decide not to render after attach_render (e.g. when
there's nothing new to render to the back buffer). Thus
wlr_output_rollback has been introduced to revert the pending state.
Because the output backend API is mostly state-less, the only thing
wlr_output_impl.rollback needs to do is revert the current rendering
context. Rename the function to rollback_render to make this clear. Add
a check in the common wlr_output code to only call rollback_render when
attach_buffer has been previously called.
On the long term, we'll be able to remove attach_render and
rollback_render together.
Most of the pending output state is not forwarded to the backend prior
to an output commit. For instance, wlr_output_set_mode just stashes the
mode without calling any wlr_output_impl function.
wlr_output_impl.commit is responsible for applying the pending mode.
However, there are exceptions to this rule. The first one is
wlr_output_attach_render. It won't go away before renderer v6 is
complete, because it needs to set the current EGL surface.
The second one is wlr_output_attach_buffer.
wlr_output_impl.attach_buffer is removed in [1].
When wlr_output_rollback is called, all pending state is supposed to be
cleared. This works for all the state except the two exceptions
mentionned above. To fix this, introduce wlr_output_impl.rollback.
Right now, the backend resets the current EGL surface. This prevents GL
commands from affecting the output after wlr_output_rollback.
This patch is required for FBO-based outputs to work properly. The
compositor might be using FBOs for its own purposes [2], having leftover
FBO state can have bad consequences.
[1]: https://github.com/swaywm/wlroots/pull/2097
[2]: https://github.com/swaywm/wlroots/pull/2063#issuecomment-597614312
Check that buffer can be scanned out in wlr_output_test instead of
wlr_output_attach_buffer. This allows the backend to have access to the
whole pending state when performing the check.
This brings the wlr_output API more in line with the KMS API.
This removes the need for wlr_output_attach_buffer to return a value,
and for wlr_output_impl.attach_buffer.
This function allowed backends to provide a custom function for frame
scheduling. Before resuming the rendering loop, the DRM and Wayland
backends would wait for vsync.
There isn't a clear benefit of doing this. The only upside is that we
get more stable timings: the delay between two repaints doesn't change too
much and is close to a mutliple of the refresh rate.
However this introduces latency, especially when a client misses a
frame. For instance a fullscreen game missing vblank will need to wait
more than a whole frame before being able to display new content. This
worst case scenario happens as follows:
- Client is still rendering its frame and cannot submit it in time
- Deadline is reached
- Compositor decides to stop the rendering loop since nothing changed on
screen
- Client finally manages to render its frame, submits it
- Compositor calls wlr_output_schedule_frame
- DRM backend waits for next vblank
- The wlr_output frame event is fired, compositor draws new content on screen
- On the second next vblank, the new content reaches the screen
With this patch, the wlr_output frame event is fired immediately when
the client submits its late frame.
This change also makes it easier to support variable refresh rate, since
VRR is all about being able to present too-late frames earlier.
References: https://github.com/swaywm/wlroots/issues/1925
