On Android 14, a separate process was spawn on every display mode
request (to turn the screen off or on).
But starting a java process takes time (a few hundred milliseconds),
causing a noticeable latency between the request to turn the screen off
(MOD+o) or on (MOD+Shift+o) and the actual power mode change.
To minimize this latency, keep the process alive between requests, so
that only the first one will have to spawn the process.
It would be possible to spawn the process in advance, so that even the
first request would be immediate, but any problem would impact all
Android 14 users even without using the "turn screen off" feature.
PR #4446 <https://github.com/Genymobile/scrcpy/pull/4446>
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