Currently, each player buffers their own inputs and sends them to the
host. The host then relays those inputs to everyone else. Every player
waits on inputs from all players to be buffered before continuing. What
this means is all clients run in lockstep, and the total latency of
inputs cannot be lower than the sum of the 2 highest client ping times
in the game (in 3+ player sessions with people across the world, the
latency can be very high).
Host input authority mode changes it so players no longer buffer their
own inputs, and only send them to the host. The host stores only the
most recent input received from a player. The host then sends inputs
for all pads at the SI poll interval, similar to the existing code. If
a player sends inputs to slowly, their last received input is simply
sent again. If they send too quickly, inputs are dropped. This means
that the host has full control over what inputs are actually read by
the game, hence the name of the mode. Also, because the rate at which
inputs are received by SI is decoupled from the rate at which players
are sending inputs, clients are no longer dependent on each other. They
only care what the host is doing. This means that they can set their
buffer individually based on their latency to the host, rather than the
highest latency between any 2 players, allowing someone with lower ping
to the host to have less latency than someone else.
This is a catch to this: as a necessity of how the host's input sending
works, the host has 0 latency. There isn't a good way to fix this, as
input delay is now solely dependent on the real latency to the host's
server. Having differing latency between players would be considered
unfair for competitive play, but for casual play we don't really care.
For this reason though, combined with the potential for a few inputs to
be dropped on a bad connection, the old mode will remain and this new
mode is entirely optional.
also did these things
fixed crash from joining user that isn't hosting via a direct connection
current game stat can now pass to override the current game in config
uses ip endpoint from dolphin.org
Most settings which affect determinism will now be synced on NetPlay.
Additionally, there's a strict sync mode which will sync various
enhancements to prevent desync in games that use EFB reads.
This also adds a check for all players having the IPL.bin file, and
doesn't load it for anyone if someone is missing it. This prevents
desyncs caused by mismatched system fonts.
Additionally, the NetPlay window was getting too wide with checkboxes,
so FlowLayout has been introduced to make the checkboxes take up
multiple rows dynamically. However, there's some minor vertical
centering issues I haven't been able to solve, but it's better than a
ridiculously wide window.
Basically everything here was race conditions in Qt callbacks, so I changed the client/server instances to std::shared_ptr and added null checks. It checks that the object exists in the callback, and the shared_ptr ensures it doesn't get destroyed until we're done with it.
MD5 check would also cause a segfault if you quit without cancelling it first, which was pretty silly.
Pierre Bourdon