Right now we rely entirely on implicit sync for synchronizing
access to GPU buffers. Implicit sync works by setting
synchronization points on the buffer in writers, and letting
readers wait on these sync points before accessing the buffer.
With OpenGL, sync points are created using functions such as
eglSwapBuffers or glFlush. If none of these special functions
are called, no sync point will be created and readers will
potentially access a buffer that hasn't finished rendering yet.
In the context of wlroots, OpenGL is the writer and the backend
(KMS or parent Wayland/X11 session) is the reader. After we're
done rendering a frame, and before passing that frame to the
backend, we need to call glFlush.
glFlush is called when the buffer is detached from the renderer.
This is a task done by output_clear_back_buffer. So let's call
this function before invoking the impl->commit hook, instead of
calling it after.
All of this is maybe a little tricky to get right with the
current renderer_bind_buffer API. The new
wlr_renderer_begin_with_buffer API is much better, because glFlush
is called on wlr_renderer_end, so it's more intuitive.
Closes: https://github.com/swaywm/wlroots/issues/3020
On commit failure, we need to unbind the back buffer from the
renderer.
This fixes assertions triggered on commits following a failed commit
where the compositor called wlr_output_attach_render.
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.
Compute only the transform matrix in the output. The projection matrix
will be calculated inside the gles2 renderer when we start rendering.
The goal is to help the pixman rendering process.
- The DRM backend initially doesn't have a frame scheduled initially.
However the compositor is expected to set a mode to start the
rendering loop (frame_pending is set to true in drm_crtc_pageflip).
- The headless and X11 backends have a timer to schedule frames, so they
ignore this hint completely.
- The Wayland backend renders a fake frame to start the rendering loop.
It's the only case where a frame is pending on init, move the
assumption there.
wlr_surface_send_enter now stores outputs that have been entered.
Combined with a new 'bind' event on wlr_output, this allows us to delay
enter events as necessary until the respective wl_output global has been
bound.
Closes: https://github.com/swaywm/wlroots/issues/2466
This event contains a `committed` bitfield, which allows callers to know
which output fields changed during the commit.
This allows users to setup a single atomic commit listener, instead of
setting up one listener for each event (mode, scale, transform, and so
on).
References: https://github.com/swaywm/wlroots/issues/2098
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.
GCC is complaining about a maybe-uninitialized variable when doing a
release build. Even if that can't actually happen because all enum
values are handled, add an abort call to silence the warning.
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.
Consumers call wlr_buffer_lock. Once all consumers are done with the
buffer, only the producer should have a reference to the buffer. In this
case, we can release the buffer (and let the producer re-use it).
This patch disambiguates the needs_frame event by uncoupling it from
damage. A new separate damage event is emitted when the backend damages
the output (this happens e.g. VT is changed or software cursors are
used). The event specifies the damaged region.
The wlr_output.damage field is removed. wlr_output is no longer
responsible for tracking its own damage, this is wlr_output_damage's
job.
This is a breaking change, but wlr_output_damage users shouldn't need an
update.
Bugs fixed:
- Screen flashes on VT switch
- Cursor damage issues on the X11 and headless backends
Closes: https://github.com/swaywm/sway/issues/5086
This way, wlr_output_schedule_frame will always be followed by a
wlr_output_commit. This forces the compositor to render an extra
frame before stopping the rendering loop.
To test, run wleird's frame-callback [1], make sure it's the only
visible client on the output and check the interval between frame
events is the output's refresh period instead of zero.
[1]: https://github.com/emersion/wleird/blob/master/frame-callback.c
Closes: https://github.com/swaywm/wlroots/issues/2051
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
This change ensures that wlr_output_transform_compose correctly composes
transforms when the first transform includes a rotation and the second
transform includes a flip.
wlr_output.description is a string containing a human-readable string
identifying the output. Compositors can customise it via
wlr_output_set_description, for instance to make the name more
user-friendly.
References: https://github.com/swaywm/wlroots/issues/1623
Backends not supporting presentation feedback call
wlr_output_send_present with a NULL event in their commit handler. Since
the commit hasn't been applied yet, commit_seq still has its old value.
We need to increment it.
An alternative would be to move commit_seq in wlr_output_state. This
would allow to have a pending and a current commit_seq.
wlr_output_send_present could take the pending commit_seq when called
with a NULL event.
