This is to allow for compositors that want to be more implicit about
how their scene is organized. Such a compositor may want to walk up
at a certain scene node to find something such as a surface to focus on.
...when only one edge is anchored.
The layer-shell protocol specifies that a positive exclusive-zone value is
'meaningful' if the surface is anchored to either:
1. one edge
2. one edge and both perpendicular edges.
For example, if you wish to position a layer-shell client along the top
edge and make it exclusive, you should be able to either set anchor=TOP or
anchor=TOP|LEFT|RIGHT. It appears that many panels/bars use the latter
approach (anchor to an edge and also both perpendicular edges) which is
probably why this has not been reported previously.
This patch adds support for the first case and thereby makes exclusive
zone behaviour consistent with the protocol and also with sway's extant
layer-shell implementation.
Now, it is checked whether an output pixel corresponds to an integer
number of buffer pixels; if it doesn't, the region is altered to take
this into account.
This allows the backend to have access to the frame damage, as
reported by the scanned-out client. Some KMS drivers can make use
of it (e.g. for PSR, or optimized USB transfers in the GUD driver),
and the Wayland/X11 backends forward it to the parent compositor.
The concept of a persistent accumulated surface offset is wrong
from a protocol point-of-view. wl_surface.offset is tied to a
commit, its interpretation depends on the surface role.
For example, with the following sequence:
wl_surface@1.offset(1, 1)
wl_surface@1.commit()
wl_pointer@2.set_cursor(wl_surface@1, 42, 42)
The final cursor hotspot is (42, 42): the commit which happened
before the set_cursor request has no impact on the hotspot
computation.
The wlr_output_cursor logic already uses wlr_surface.current.{dx,dy}.
wlr_scene's drag icon doesn't, update it accordingly.
If a new buffer is set for a buffer node, we must update the entire
node unconditionally if the buffer size changes, or the buffer is given
a buffer where it was previously NULL.
While we're here, let's avoid calling scene_node_update on just damage
updates. If the caller hasn't given us a damage region we just assume
the whole buffer.
If the area calculations for output overlap overflow a signed int, we
may not consider it to be a primary output. Turn this into an unsigned
type so this happens less frequently.
Additionally, it is possible the overflow would produce 0, we can handle
this by simply changing the comparison to more than or equal.
While we're here, let's assert that we always assign a primary output
if there are any intersecting outputs.
Originally, I thought that we could safely subtract opaque regions
from the background even if the black rect optimization was kicking in.
This is wrong because a scene node that isn't fully occluded will still
appear in the render list even if its partially under a black rect. We
need to make sure that while culling the background, we only consider
opaque regions that are also visible. This will fix the black rect
optimization with the background.
