Genymobile/scrcpy

Extension is deliberately table-driven. Client CLI: add an OPT_* enum + options[] row + case in the getopt switch + field in scrcpy_options. Server options: mirror the param as an ADD_PARAM in execute_server() and a case in Options.parse(). New control messages require a coordinated change in enum sc_control_msg_type, sc_control_msg_serialize/is_droppable/destroy/log, ControlMessage type constants, ControlMessageReader parsing and Controller.handleEvent dispatch. New media sinks plug into the packet_source/packet_sink and frame_source/frame_sink trait interfaces; new input modalities implement key/mouse/gamepad processor interfaces (SDK/UHID/AOA are the three existing backends). Server-side work units implement AsyncProcessor; captures implement SurfaceCapture; audio sources implement AudioCapture.

• Adding a CLI option = new OPT_* enum entry + a row in the static options[] table (shortopt/longopt/argdesc/optional_arg/text) + handling in parse_args_with_getopt's switch; undocumented options are supported by leaving .text NULL.
  app/src/cli.c#L22-149app/src/cli.c#L1431
• Client->server option plumbing is a three-step mirror: sc_server_params field -> ADD_PARAM("key=value") in execute_server() -> case "key" in Options.parse() switch.
  app/src/scrcpy.c#L365-425app/src/server.c#L269-458server/src/main/java/com/genymobile/scrcpy/Options.java#L336-574
• New control message types must be added symmetrically: enum sc_control_msg_type + serialize/log/droppable/destroy cases client-side, and ControlMessage.TYPE_* + ControlMessageReader.read() case + Controller.handleEvent dispatch server-side.
  app/src/control_msg.h#L29-53app/src/control_msg.c#L103-211server/src/main/java/com/genymobile/scrcpy/control/ControlMessageReader.java#L25-70server/src/main/java/com/genymobile/scrcpy/control/Controller.java#L333-441
• The trait/ directory defines generic producer/consumer interfaces (packet_source/packet_sink for AVPackets, frame_source/frame_sink for AVFrames); recorder, decoders, screen, v4l2_sink and regulators all plug in via *_add_sink without knowing each other.
  app/src/trait/packet_source.happ/src/trait/frame_source.happ/src/scrcpy.c#L555-589
• Input backends implement narrow processor interfaces (sc_key_processor, sc_mouse_processor, sc_gamepad_processor in trait/); scrcpy.c picks sdk/uhid/aoa implementations into union members and passes them to the screen as kp/mp/gp.
  app/src/trait/key_processor.happ/src/trait/mouse_processor.happ/src/trait/gamepad_processor.happ/src/scrcpy.c#L706-766
• Server capture sources implement SurfaceCapture — ScreenCapture, NewDisplayCapture, CameraCapture — selected by videoSource/newDisplay in Server.scrcpy() and attached to SurfaceEncoder.
  server/src/main/java/com/genymobile/scrcpy/Server.java#L139-155server/src/main/java/com/genymobile/scrcpy/video/SurfaceCapture.java
• Audio capture is pluggable via AudioCapture implementations AudioDirectCapture and AudioPlaybackCapture chosen by AudioSource.isDirect().
  server/src/main/java/com/genymobile/scrcpy/Server.java#L119-127server/src/main/java/com/genymobile/scrcpy/audio/AudioCapture.java
• Server-side background work implements the AsyncProcessor interface (start/stop/join + TerminationListener); Server keeps a List<AsyncProcessor> it starts and joins uniformly.
  server/src/main/java/com/genymobile/scrcpy/AsyncProcessor.javaserver/src/main/java/com/genymobile/scrcpy/Server.java#L103-195
• Adding a codec means extending enum sc_codec, sc_server_get_codec_name, the demuxer SC_CODEC_ID_* mapping to AVCodecID, and the server-side VideoCodec/AudioCodec enums with matching wire ids.
  app/src/server.c#L105-130app/src/demuxer.c#L19-58server/src/main/java/com/genymobile/scrcpy/video/VideoCodec.java
• Custom SDL event types (SC_EVENT_*) in events.h + sc_push_event provide the extension mechanism for cross-thread signaling into the main event loop.
  app/src/events.happ/src/scrcpy.c#L116-153
• Recording formats extend enum sc_record_format -> sc_recorder_get_format_name() mapping to FFmpeg muxer names (mp4/matroska/opus/flac/wav).
  app/src/recorder.c#L64-83
• Feature flags compile out whole subsystems: HAVE_USB gates OTG/AOA code, HAVE_V4L2 gates the webcam sink, SERVER_DEBUGGER adds jdwp flags to the app_process command.
  app/meson.build#L104-119app/src/server.c#L225-249meson_options.txt