Modesets require a buffer. The DRM backend tried to auto-enable
outputs when a CRTC becomes available in the past, but now that
fails because no buffer is available.
Instead of having this magic inside the DRM backend, a better
approach is to do it in the compositor or in an optional helper.
On modeset wlr_output will internally allocate a buffer. The
backend will emit a "mode" output event, then wlr_output will
emit a "commit" event.
wlr_output_damage handles the "mode" event by damaging the whole
output, and then handles the "commit" event. However the commit
event has a buffer, so wlr_output_damage rotates the damage in its
ring buffer, thinking the compositor has rendered a frame. The
compositor hasn't rendered a frame, what wlr_output_damage sees is
the internal wlr_output black buffer used for the modeset.
Let's fix this by damaging the whole output in the "commit" event
handler if the mode has changed. Additionally, damage the whole
output after rotating the damage ring buffer.
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.
Caching frame callback lists is actually the correct behavior, because
if a surface is locked because of e.g. subsurface synchronization,
clients would expect to receive frame done events only after the
pending state is actually committed.
This function behaves like allocate_shm_file, except it also
returns a read-only FD. This is useful to share the same segment
of memory with many Wayland clients.
Add RECT nodes to the scene-graph demo to illustrate how they are used.
Here, we add a solid rectangle behind each surface as a quick-and-dirty
border, handling surface.commit in order to size it appropriately.
With the addition of a non-surface node type, it was unclear how such
nodes should interact with scene_node_surface_at(). For example, if the
topmost node at the given point is a RECT, should the function treat
that node as transparent and continue searching, or as opaque and return
(probably) NULL?
Instead, replace the function with one returning a scene_node, which
will allow for more consistent behavior across different node types.
Compositors can downcast scene_surface nodes via the now-public
wlr_scene_surface_from_node() if they need access to the surface itself.
RECT is a solid-colored rectangle, useful for simple borders or other
decoration. This can be rendered directly using the wlr_renderer,
without needing to create a surface.
Commits named "Fix #XXX" make it pretty complicated to figure out
exactly what the commit is doing from the shortlog. A better place
for issue references is in the extended commit message.
For consistency with the rest of the scene-graph API, prevent detaching
a subtree by giving NULL for the new parent, and don't allow ROOT nodes
to be grafted into another tree.
If nodes are arranged in a tree rather than at a single level, then it
makes sense that there should be a way to move them to a completely
different parent in addition to moving up or down among siblings.
