Polyseat 0.37.0

A stream stuttered with nothing wrong with it. On a wired connection, with
every statistic on the client clean, a game streamed out of a seat still
hitched a few times a second. It was not the network and not the encoder: 60.00
frames a second left the seat and not a packet was lost. Five to eleven of
every hundred frames were the picture before, sent again, and for each of those
another one was never sent.

The cause was Sunshine's capture on sway. It asked for a frame on a clock of its
own, which made sway produce one whether the game had drawn anything new or
not, and depending on how that clock happened to stand against the game's the
same picture went out twice. A seat now runs the same Sunshine release with one
patch that takes a frame when sway has a new one, and its output runs at twice
the rate the client asked for, so that a frame the game delivers a little early
has somewhere to go. Measured on the same seat, game and client, before and
after: 5 to 11 repeats in a hundred down to none, at 60.00 frames a second,
over seven connections.

Both halves are needed and each was measured without the other. The patch alone
delivered 54 to 57 frames a second, and the faster output alone was clean on one
connection and one repeat in ten on the next.

A seat's Sunshine is built here now. It is LizardByte's 2026.914.233613
with packaging/sunshine/wlgrab-event-driven.patch, published as a package on
a release of this repository and checked against a checksum in the source
before it is installed. The web interface of that Sunshine names Polyseat as
its publisher, so that a problem with it is brought here. The recipe and how to
build it are in packaging/sunshine. The change itself is open with LizardByte
as #5751 and #5748; when a release of theirs carries it, the seats go back to
their package.

The interface shows twice the client's rate while somebody is streaming. A
seat serving a 60 fps client reads 3840x2160@120Hz now. That is the output's
rate and it is meant to be; the stream is still the 60 the client asked for.

Not measured: a client asking for 120 frames a second, which puts the
output at 240 Hz; a game running directly on sway rather than through Steam;
and an AMD host, where the package is the same but the encoder is not.

Seats have to be built again for this: recipe generation 65. Provisioning
replaces the Sunshine package and the script that sizes the output. A seat
built before keeps stuttering exactly as it did.