This implements the modifier fixation procedure. The producer of a
stream has to ensure that it can create a buffer with the negotiated
properties. To do that we will take the result of the intersection of
supported modifiers by PipeWire and select the "best" modifier from that
list.
To do this we do the following allocations and fixate on the
modifier of the created buffer should the allocation suceed.
* Try to allocate a buffer with explicit modifiers using the list
provided by PipeWire
* Walk the list of modifiers and do single allocations for implicit and
linear modifiers using the old api.
If none of the allocations above succeed we fall back to shm buffers.
This is implemented in the next commit.
If an allocation was successfull we fixate the modifier with
fixate_format().
This function creates an EnumFormat like build_format, but will only
announce support for a single modifier.
It is used to finish the negotiation process by announcing it together
with EnumFormats of our full supported formats.
Using SPA_POD_PROP_FLAG_DONT_FIXATE pipewire can return a list of
supported modifiers. In that case are we responsible to select one
modifier and fixate it.
Dequeuing a new buffer imidiately creates a problem when the buffer is
destroid while renegotiation of a valid modifier because we can end up using
a buffer which was freed while waiting for the buffer_done event. Then
xdpw will segfault when requesting a copy with a nonexisting buffer. To fix
this we can just dequeue a buffer right before we need it. This makes
the fallback via on_process obsolete since we dequeue the buffer at the
lates possible time.
We should log buffer add and remove events in the debug loglevel, since
they signal starts, stops and renegotiations of the buffer transfer.
Additionaly logging the negotiated pwr_format should help classify
issues from the DEBUG loglevel.
Clients have wrongly used the chunk size to detect if a buffer was valid
or not. Since dmabufs might not have a well defined buffer size we will
set an arbitrary value until clients are patched.
This is using the older gbm api without support for explicit modifiers.
This is required to support AMD gpus using the GFX8 or older
architecture and older intel gpus.
When announcing support for dmabufs via PipeWire this is done by adding
the SPA_FORMAT_VIDEO_modifier property to an EnumFormat. Producers can
choose between two different ways [1]:
* Supporting only implicit modifiers by adding the property as a sigle
value together with the SPA_POD_PROP_FLAG_MANDATORY flag
* Support for multiple modifiers. This is done by announcing a
SPA_CHOICE_ENUM array together with the use of the
SPA_POD_PROP_FLAG_MANDATORY and SPA_POD_PROP_FLAG_DONT_FIXATE flag
[1] https://docs.pipewire.org/page_dma_buf.html
We want to support WL_SHM and DMABUFS based buffers. The buffer_type
member tracks the type of a xdpw_buffer and screencopy_frame_info of the
screencast_instance will be an array with an element for each buffer type
indexed by the value of the buffer_type enum. Only members of the
xdpw_screencopy_frame_info relevant to the buffer type should be used.
We build EnumFormats from our supported format multiple times. This
commit just creates a function to do that. This makes it easier to
handle the announcement of multiple buffer types.
drm format defined by drm_fourcc.h is the standard to describe the
format of a buffer. This will be used when dealing with dmabufs and to
simplify things we should drm_formats for all internal structs.
In case a client doesn't return a buffer early enough we can give it a
second chance by triggering on_process before we pass the buffer to
wlroots in the frame_buffer_done event.
The previous implemented way to use wlr_screencopy events to cicle the
screencast had issues, like halting the stream if it was paused and
resumed before PipeWire triggered a recreation of buffers. This came
from not returning a dequeued buffer. This is now mititgated by
enqueuing the current pw_buffer imidiately on a paused event and trying
to dequeue a buffer just before requesting a screencopy if none is
present.
It showed that handling self contained buffers is much easier then have
the metadata of the buffer seperated from the actual buffer attached to
the screencast instance.
The goal of the following changes is to separate the meta informations
like requested buffer attributes and wlr_screencast data from the actual
buffers.
This enables us to:
* Simplify the flow between the PipeWire loop and the wlroots one
* Track and apply damage to each used buffer (ext_screencopy)
We can trigger that with pw_stream_trigger_process when we are the
driver of the stream. Additionally this let's us run passivly with the
consumer driving the stream.
PipeWire can request to destroy the allocated buffers anytime. This
isn't a problem for us, since the screencopy protocol can handle
disappearing buffers. The only thing we have to do is not to use a
destroyed buffer.
The enum xdpw_frame_state is used to track the state of the xdpw_frame through
the screencopy callbacks. xdpw_wlr_stream_finish is used as the new
endpoint of the screencopy callbacks. Here we clean up the
screencopy_frame, enqueue the pipewire buffer and restart the screencopy
loop if needed.
Instead of using one wl_buffer to export buffers from wlroots and then
copy the content into the buffer dequed from pipewire, we can create a
wl_buffer for each pipewire buffer directly at allocation time and
attach it to the data attribute. Those wl_buffers can be directly handed
over to the wlroots screencopy protocol and so removing one copy.
Since we are driving the screencast there are no events on the pipewire loop
calling the on_event callback. We want to import and export (if possible) on
every frame of the wlroots loop, so this event is no longer needed.
The default node_id is SPA_ID_INVALID.
We are casting pipewire uint32_t node_id to int for printing since they are
currently staying in the range of low integer numbers. This makes
spotting an uninitialized node_id (casted to -1) much easier. Should be
corrected if that becomes an issue in the future.
Make sure that in SPA_POD_CHOICE_ENUM_Id(n_vals, ...) we always pass
exactly n_vals arguments. For this we build the object with separate
spa_pod_builder_add calls, since n_vals is known at runtime.
Fix#102
