protocols: implement a remote control protocol based on MIDI

Based on reverse engineering done by this wonderful team:

https://github.com/NicoG60/TouchMCU

cmake/libremidi.examples.cmake

@@ -1,15 +1,16 @@
 macro(setup_example _example)
-  target_link_libraries(${_example} PRIVATE libremidi)
+  target_link_libraries("${_example}" PRIVATE libremidi)
 endmacro()
 
 macro(add_example _example)
-  add_executable(${_example} examples/${_example}.cpp)
-  setup_example(${_example})
+  string(REPLACE "/" "_" _exampleName "${_example}")
+  add_executable("${_exampleName}" "examples/${_example}.cpp")
+  setup_example("${_exampleName}")
 endmacro()
 
 macro(add_backend_example _example)
-    add_executable(${_example} examples/backends/${_example}.cpp)
-    setup_example(${_example})
+    add_executable("${_example}" "examples/backends/${_example}.cpp")
+    setup_example("${_example}")
 endmacro()
 
 add_example(midiobserve)
@@ -27,6 +28,8 @@ add_example(minimal)
 add_example(midi2_echo)
 add_example(rawmidiin)
 
+add_example(protocols/remote_control)
+
 if(LIBREMIDI_NI_MIDI2)
   add_example(midi2_interop)
 endif()

examples/protocols/remote_control.cpp

@@ -0,0 +1,97 @@
+#include <libremidi/libremidi.hpp>
+#include <libremidi/protocols/remote_control.hpp>
+
+#if __has_include(<magic_enum_all.hpp>)
+  #include <magic_enum_all.hpp>
+#else
+  #include <iomanip>
+  #include <iostream>
+  #include <sstream>
+namespace magic_enum
+{
+std::string enum_name(auto cmd)
+{
+  std::stringstream ss;
+  ss << "0x" << std::setbase(16) << static_cast<uint32_t>(cmd);
+  return ss.str();
+}
+}
+#endif
+
+#include <cstdlib>
+#include <ctime>
+#include <iostream>
+
+int main()
+{
+  auto api = libremidi::API::ALSA_SEQ;
+  libremidi::observer observer{{.track_any = true}, api};
+  if (observer.get_input_ports().empty())
+    return 1;
+  if (observer.get_output_ports().empty())
+    return 1;
+
+  libremidi::input_port ip;
+  libremidi::output_port op;
+
+  // Tested with https://github.com/NicoG60/TouchMCU
+  for (auto& p : observer.get_input_ports())
+    if (p.port_name == "TouchOSC")
+      ip = p;
+  for (auto& p : observer.get_output_ports())
+    if (p.port_name == "TouchOSC")
+      op = p;
+
+  if (ip.port_name.empty() || op.port_name.empty())
+  {
+    std::cerr << "No device found !";
+    return 1;
+  }
+
+  // Create the midi out port
+  libremidi::midi_out midi_out{{}, api};
+
+  // Set-up the remote control API.
+  // Here we only do some logging, this is where commands sqall be handled.
+  libremidi::remote_control_processor rcp{{.midi_out = [&](libremidi::message&& msg) {
+    midi_out.send_message(msg);
+  }, .on_command = [](libremidi::remote_control_protocol::mixer_command cmd, bool pressed) {
+    std::cerr << "command: " << magic_enum::enum_name(cmd) << " -> "
+              << (pressed ? "pressed" : "released") << "\n";
+  }, .on_control = [](libremidi::remote_control_protocol::mixer_control ctl, int v) {
+    std::cerr << "control: " << magic_enum::enum_name(ctl) << " -> " << v << "\n";
+  }, .on_fader = [](libremidi::remote_control_protocol::fader f, uint16_t v) {
+    std::cerr << "fader: " << magic_enum::enum_name(f) << " -> " << v << "\n";
+  }}};
+
+  // Initialize the midi in port
+  libremidi::midi_in midi_in{
+      {.on_message = [&](const libremidi::message& message) { rcp.on_midi(message); }}, api};
+
+  // Open the ports
+  if (auto err = midi_in.open_port(ip); err != stdx::error{})
+    err.throw_exception();
+
+  if (auto err = midi_out.open_port(op); err != stdx::error{})
+    err.throw_exception();
+
+  // Start communication
+  rcp.start();
+
+  // Blast messages :)
+  using proto = libremidi::remote_control_protocol;
+  unsigned i = 0;
+  for (;;)
+  {
+    usleep(1e4);
+
+    std::time_t result = std::time(nullptr);
+    auto ctime = std::localtime(&result);
+    rcp.update_timecode(ctime->tm_hour, ctime->tm_min, ctime->tm_sec, 0);
+    rcp.update_lcd(std::string(1, '\0' + i % 127), i % 112);
+    rcp.fader(static_cast<proto::fader>(i % 8), (200 * i) % 16384);
+    i++;
+  }
+
+  return 0;
+}