Kaleidoscope/UPGRADING.md

Upgrading from Focus to onFocusEvent + FocusSerial

Upgrading from Focus to onFocusEvent and FocusSerial is a reasonably simple process, the interface is quite similar. Nevertheless, we present a step-by-step guide here, covering two use cases: one where we wish to always provide a Focus command when both our plugin and FocusSerial are enabled; and another where we only wish to provide the command when explicitly asked to do so.

The most trivial example

The biggest difference between Focus and onFocusEvent is that the former required explicit registering of hooks, while the latter does it automatically: every plugin that implements the onFocusEvent method will be part of the system. As a consequence, only plugins are able to supply new commands: there is no explicit registration, thus, no way to inject a command that isn't part of a plugin. This also means that these functions now return kaleidoscope::EventHandlerResult instead of bool. Lets see a trivial example!

Focus

bool exampleFocusHook(const char *command) {
  if (strcmp_P(command, PSTR("example")) != 0)
    return false;

  Serial.println(F("This is an example response. Hello world!"));

  return true;
}

KALEIDOSCOPE_INIT_PLUGINS(Focus)

void setup() {
  Serial.begin(9600);
  Kaleidoscope.setup();
  Focus.addHook(FOCUS_HOOK(exampleFocusHook, "example"));
}

onFocusEvent

namespace kaleidoscope {
class FocusExampleCommand : public Plugin {
 public:
  FocusExampleCommand() {}

  EventHandlerResult onFocusEvent(const char *command) {
    if (strcmp_P(command, PSTR("example")) != 0)
      return EventHandlerResult::OK;

    Serial.println(F("This is an example response. Hello world!"));
    return EventHandlerResult::EVENT_CONSUMED;
  }
};
}

kaleidoscope::FocusExampleCommand FocusExampleCommand;

KALEIDOSCOPE_INIT_PLUGINS(Focus, FocusExampleCommand);

void setup() {
  Kaleidoscope.setup();
}

Summary

The new version is slightly more verbose for the trivial use case, because we have to wrap it up in an object. But other than that, the changes are minimal, and we don't need to explicitly register it!

Observe that the return values changed: with Focus, if we wanted other hooks to have a chance at processing the same command, the hook returned false; if we wanted to stop processing, and consider it consumed, it returned true. With the new system, this is more descriptive with the EventHandlerResult::OK and EventHandlerResult::EVENT_CONSUMED return values.

A stateful example

Perhaps a better example that shows the quality of life improvements the new system brings is the case where the command needs access to either plugin state, or plugin methods. With the former system, the focus hooks needed to be static methods, and needed to be public. This is not necessarily the case now, because onFocusEvent is a non-static object method. It has full access to plugin internals!

Focus

namespace kaleidoscope {
class ExamplePlugin : public Plugin {
 public:
  ExamplePlugin();

  static bool exampleToggle() {
    example_toggle_ = !example_toggle_;
    return example_toggle_;
  }

  static bool focusHook(const char *command) {
    if (strcmp_P(command, PSTR("example.toggle")) != 0)
      return false;

    ::Focus.printBool(exampleToggle());
    return true;
  }

 private:
  static bool example_toggle_;
};
}

kaleidoscope::ExamplePlugin ExamplePlugin;

KALEIDOSCOPE_PLUGIN_INIT(Focus, ExamplePlugin)

void setup() {
  Serial.begin(9600);
  Kaleidoscope.setup();

  Focus.addHook(FOCUS_HOOK(ExamplePlugin.focusHook, "example.toggle"));
}

onFocusEvent

namespace kaleidoscope {
class ExamplePlugin : public Plugin {
 public:
  ExamplePlugin();

  EventHandlerResult onFocusEvent(const char *command) {
    if (strcmp_P(command, PSTR("example.toggle")) != 0)
      return EventHandlerResult::OK;

    example_toggle_ = !example_toggle_;
    ::Focus.printBool(example_toggle_);

    return EventHandlerResult::EVENT_CONSUMED;
  }

 private:
  static bool example_toggle_;
};
}

kaleidoscope::ExamplePlugin ExamplePlugin;

KALEIDOSCOPE_PLUGIN_INIT(Focus, ExamplePlugin)

void setup() {
  Kaleidoscope.setup();
}

Summary

It's just another plugin, with just another event handler method implemented, nothing more. No need to explicitly register the focus hook, no need to provide access to private variables - we can just keep them private.

Optional commands

Optional commands are something that were perhaps easier with the Focus method: one just didn't register them. With onFocusEvent, we need to do a bit more than that, and move the command to a separate plugin, if we do not wish to enable it in every case. This adds a bit of overhead, but still less than Focus did.

Focus

bool exampleOptionalHook(const char *command) {
  if (strcmp_P(command, PSTR("optional")) != 0)
    return false;

  Serial.println(Layer.getLayerState(), BIN);
  return true;
}

KALEIDOSCOPE_INIT_PLUGINS(Focus)

void setup() {
  Kaleidoscope.setup();
}

Do note that we do not register the exampleOptionalHook here! As such, because it is unused code, it will get optimized out during compilation. While this is a simplistic example, the optional hook might have been part of a class, that provides other hooks.

onFocusEvent

namespace kaleidoscope {
class ExampleOptionalCommand : public Plugin {
 public:
  ExampleOptionalCommand() {}

  EventHandlerResult onFocusEvent(const char *command) {
    if (strcmp_P(command, PSTR("optional")) != 0)
      return EventHandlerResult::OK;

    Serial.println(Layer.getLayerState(), BIN);
    return EventHandlerResult::EVENT_CONSUMED;
  }
};
}

KALEIDOSCOPE_INIT_PLUGINS(Focus)

void setup() {
  Kaleidoscope.setup();
}

Summary

The trick here is to move optional commands out into a separate plugin. It's a bit more boilerplate, but not by much.