Enable scene-tree direct scanout of a single buffer with various options
for scaling and source crop. This is intended to support direct scanout
for fullscreen video with/without scaling, letterboxing/pillarboxing
(e.g. 4:3 content on a 16:9 display), and source crop (e.g. when
1920x1088 planes are used for 1920x1080 video).
This works by explicitly specifying the source crop and destination box
for the primary buffer in the output state. DRM atomic and libliftoff
backends will turn this into a crop and scale of the plane (assuming the
hardware supports that). For the Wayland/X11/DRM-legacy backends I just
reject this so scanout will be disabled.
The previous behaviour is preserved if buffer_src_box and buffer_dst_box
are unset: the buffer is displayed at native size at the top-left of the
output with no crop.
The change to `struct wlr_output_state` makes this a binary breaking
change (but this works transparently for scene-tree compositors like
labwc after a recompile).
Since wlr_damage_ring now only works with buffer local coordinates, this
creates an inpedance mismatch for compositors that want to use this
function. Instead of compositors needing to the the conversion itself,
change thu function to take buffer local coordinates directly.
This wasn't that great:
1. Now that damage ring tracks damage across actual wlr_buffer objects,
it can use the buffer size to do any sort of cropping that needs to
happen.
2. The damage ring size really should be the size of the transformed
size of the output. Compositors currently have to call
`wlr_damage_ring_set_bounds()` where it might not be clear when to
call the function. Compositors can just check against the actual
output bounds that they care about when processing the damage.
Fixes: #3891
It was completely wrong: according to the protocol, the effective
geometry is only updated on commit time if there pending state has
new state from xdg_surface.set_window_geometry or
xdg_surface.set_window_geometry has never been sent at all.
This commit adds wlr_xdg_surface.geometry which correctly matches the
effective window geometry and removes now-useless
wlr_xdg_surface_get_geometry().
It seems that some scene compositors want to avoid wlr_scene_output_commit
and use the lower lever wlr_scene_output_build_state. However, build
state does not early return if a frame is not needed so compositors will
implement the check themselves. Let's add a helper function that compositors
can use to implement the check.
Technically pending_commit_damage is a private interface, so this lets
compositors not interface with private interfaces to implement the check.
This fixes direct scanout VRR. As direct scanout buffers are not part
of the swapchain, we would mistakenly union instead of subtract the damage
meaning it will just accumulate indefinitely.
The reason for this existing in the first place is for compositors that
might want to sidestep scene and commit their own buffers to the output.
In this case, scene could theoretically acknowledge that and update the
damage. Except, this really didn't work because WLR_OUTPUT_STATE_DAMAGE
would need to be defined which is optional. This patch also properly
acknowledges commits without damage.
In the use case of a weird compositor that might want to sidestep scene,
they can just trash the damage ring themselves.
Fixes: #3871
There were two problems with the old implementation:
1. wlr_scene_output_commit would bail early if a frame wasn't requested
and there was no commit damage, however commit damage could never accumulate
until rendering happens. The check was subtly wrong as a result.
2. Previously, we would fill the pending commit damage based on the
current state of the damage ring. However, during direct scanout, the
damage would accumulate which would mean we would submit damage from
previous frames even if we didn't need to.
The old logic might not update the entire scene node when a node is
disabled. It would only consider the damage last time (the damage was
based on the visible region of the node).
It's important that we update the entire node region because xwayland
stacking will depend on this.
We were relying on the fact that we wouldn't paint anything on top
of the black background in the region of a black rect. However
when fractional scaling is used the repaint region might get
expanded to nearby pixels by scale_output_damage(). As a result
the neighbour scene nodes might leak into the skipped black rect's
region.
Avoid this by using this optimization for bottom-most black rects
only when fractional scaling is used.
References: https://github.com/swaywm/sway/issues/8233
If we need to apply a color transform to rendered content, we will not
be able to use direct scanout. Explicitly skip it to not accidentally
show frames lacking the color transform.
Clients may, for example, commit an exclusive zone larger than the
output dimensions. Compositors must handle this gracefully, which likely
requires more work on the compositor side but returning a usable area
with negative width or height in wlr_scene_layer_surface_v1_configure()
is nonsensical.
