Add fdm_signal_add() and fdm_signal_del(). Signals added to the fdm
will be monitored, and the provided callback called as “soon as
possible” from the main context (i.e not from the signal handler
context).
Monitored signals are *blocked* by default. We use epoll_pwait() to
unblock them while we’re polling. This allows us to do race-free
signal detection.
We use a single handler for all monitored signals; the handler simply
updates the signal’s slot in a global array (sized to fit SIGRTMAX
signals).
When epoll_pwait() returns EINTR, we loop the global array. The
callback associated with each signal that fired is called.
Shutdown the terminal when the client process terminates, not when the
ptmx file descriptor is closed.
This fixes an issue where the terminal remains running after the
client process has terminated, if it spawned child processes that
inherited the ptmx file descriptor.
We may want to be able to enable/disable IME run-time, even though we
have received an ‘enter’ IME event.
This enables us to do that.
Also add functions to enable/disable IME on a per-terminal instance
basis.
A terminal may have multiple seats focusing it, and enabling/disabling
IME in a terminal instance enables/disables IME on all those seats.
Finally, the code to enable IME is simplified; the *only* surface that
can ever receive ‘enter’ IME events is the main grid. All other
surfaces are sub-surfaces, without their own keyboard focus.
fdm_ptmx(), the FDM callback handler for ptmx data, is just as much in
the hot path as vt_from_slave(). It is also slightly more complicated
than a read() followed by a call to vt_from_slave().
As a result, some benchmarks performed significantly worse in a
partial PGO build than in a full PGO build, since fdm_ptmx() wasn’t
PGO:d.
To be able to feed data through fdm_ptmx(), we need to set up the
delayed rendering timer FDs, configure the timeout values, and provide
a readable FD it can read the VT data from.
The latter is done with a memory FD. This ensures *all* VT data is
loaded into memory before we feed it to the parser.
